Neuroscience Glossary | Neurology | Washington University in St. Louis

Neuroscience Glossary | Neurology | Washington University in St. Louis
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This glossary is intended as a resource for those looking to expand their knowledge of the field of neuroscience.
Allyson Zazulia, MD
Y  Z
abducens nerve (cranial nerve VI)
motor nerve innervating the lateral rectus muscle, which
abducts
the eye; lesions of the
nucleus
, which is located in the
dorsal
pons
, produce a horizontal gaze palsy; nerve fibers exit the ventromedial pons and because of their long course are vulnerable to damage by mass lesions/increased
intracranial pressure
abduct
move away from the
sagittal
plane of the body
absence seizure (petit mal seizure)
generalized seizure
characterized by abrupt cessation of ongoing activity with a blank stare and lost or impaired consciousness lasting on average 10-20 seconds
abulia
loss of will, impulse, and decision-making ability; most commonly associated with damage to anterior cingulate cortex or its subcortical functional connections
acalculia
“inability to calculate” or difficulty with arithmetic; may be the result of damage to the
angular gyrus
in the
hemisphere
dominant for speech and language
acephalic migraine
migraine
variant consisting of the
migraine aura
without the headache; also known as migraine equivalent
accommodation
adjustment of the focal length of the lens of the eye in order to keep objects at varying distances in focus on the retina
acrocephaly
see
brachycephaly
action potential
rapid, transient, all-or-none nerve impulse initiated at the
axon
hillock; electrical signal by which the brain receives, analyzes, and conveys information
action tremor
tremor
that appears during movement of the affected body part
activities of daily living (ADLs)
activities a person performs for self-care (feeding, grooming, bathing, dressing), work, homemaking, and leisure; ability to perform ADLs is often used as a measure of ability/disability
activity limitations
difficulties an individual may have in executing specific tasks or actions (e.g., walking independently).
acute
developing over minutes to hours; implies acute metabolic dysfunction (e.g.,
ischemia
seizure
acute disseminated encephalomyelitis (ADEM)
acute, classically monophasic
demyelinative
disease of the
CNS
that may follow a viral syndrome or vaccination or no identifiable predisposing cause
adduct
move towards the
sagittal
plane of the body
Adie’s syndrome
association of
Adie’s tonic pupil
with absence of
muscle stretch reflexes
Adie’s tonic pupil
irregularly dilated pupil exhibiting minimal or no reaction to light, slow reaction to accommodation, and hypersensitivity to pilocarpine; typically
idiopathic
and most often seen in young women
adrenoleukodystrophy
typically X-linked recessive
demyelinative
disease ± adrenal dysfunction due to accumulation of very long chain fatty acids
afferent
sensory pathway proceeding toward the
CNS
from the peripheral receptor organs
afferent pupillary defect (Marcus-Gunn pupil)
pupillary dilation in the eye with a pre-chiasmic optic pathway lesion (e.g.,
optic neuritis
) in response to shining a light in the damaged eye after first shining it in the normal eye
ageusia
impaired sense of taste
agnosia
inability to recognize and interpret objects, people, sounds or smells despite intact primary sense organs (e.g., inability to identify a sound despite intact hearing); typically results from damage to the occipital or parietal lobe
agraphia
inability to communicate ideas in written language not due to mechanical dysfunction; typically results from damage to the parietal lobe.
akathisia
motor restlessness; inability to sit still
akinesia
paucity of movement
akinetic mutism
disorder of consciousness characterized by periods of sleep and periods of wakefulness during which the patient lies with eyes open but is unresponsive, mute and immobile; often due to frontal lobe damage
alexia
inability to read, usually due to a lesion of dominant occipitotemporal
cortex
alien hand syndrome
syndrome characterized by the involuntary movement of a single upper limb in conjunction with the experience of estrangement from or personification of the movements of the limb; often seen in
corticobasal degeneration
allodynia
condition in which an ordinarily painless stimulus is experienced as being painful
alpha motor neurons
large motor
neurons
that innervate extrafusal skeletal muscle fibers
alpha-synuclein
protein expressed predominantly in the
CNS
that when aggregated, can result in neurodegenerative diseases such as
Parkinson disease
dementia
with Lewy bodies and
multisystems atrophy
Alzheimer’s disease
most common cause of
dementia
in older adults; a neurodegenerative disease characterized by the gradual loss of cognitive ability in association with the neuropathological findings of abnormal protein aggregates (
neuritic plaques
and
neurofibrillary tangles
) and
neuron
loss in the
cerebral cortex
amaurosis fugax
temporary loss of vision in one eye due to impairment of blood supply through the
internal carotid artery
or the ophthalmic artery
amblyopia
developmental abnormality in which a child fails to develop sharp visual acuity
amygdala
telencephalic
gray matter
structure located in the anterior portion of the medial temporal lobe involved in emotion, cognition and the regulation of
autonomic
processes; part of the
limbic
system
amyotrophic lateral sclerosis
(ALS or Lou Gehrig’s disease) inexorably progressive and fatal disease of unknown cause characterized by slowly progressive degeneration of
upper
and
lower
motor neurons
analgesia
loss of pain sensation
anarthria
total inability to articulate speech with spared auditory comprehension and written language due to cortical, subcortical or brainstem damage
anencephaly (aprosencephaly)
CNS
malformation involving failure of closure of the
cephalic
end of the neural tube, resulting in absence of the
forebrain
and
cerebrum
; rudimentary
brainstem
may be present so that reflex actions such as breathing and responses to sound or touch may occur
aneurysm (brain aneurysm, cerebral aneurysm)
a bulging formation on an artery, usually caused by hypertension or an excessive amount of fatty deposits
angular gyrus
gyrus
located immediately posterior to the supramarginal
gyrus
at the superior edge of the temporal lobe and involved in recognition of visual symbol; lesions can result in
alexia
and
agraphia
anhidrosis
absence of sweating
anisocoria
pupillary asymmetry
ankle-foot orthosis (AFO)
brace that is worn on the lower leg and foot to support the ankle and correct foot drop
anomia
inability to name objects or to recognize written or spoken names of objects
anosmia
loss of sense of smell
anosognosia
lack of awareness of or indifference to one’s own neurological deficit, seen with nondominant parietal lobe lesions
anterior cerebral artery
a branch of the
internal carotid artery
; supplies blood to the medial aspect of the
cerebral cortex
(leg area predominant), some areas of the frontal lobe,
corpus callosum
caudate
and the anterior limb of the
internal capsule
anterior commissure
one of the three major groups of commissural fibers that courses through the
basal ganglia
and cross the midline in the anterior
forebrain
to interconnect the olfactory bulbs,
amygdala
and
hippocampal
areas, among others
anterior communicating artery
branch of the
internal carotid artery
that joins together the paired
anterior cerebral arteries
anterior cord syndrome
spinal cord injury syndrome associated with damage to the anterior 2/3 of the spinal cord, often due to occlusion of the anterior spinal artery resulting in bilateral
paralysis
, bladder dysfunction and loss of pain sensation below the level of the lesion
anterior cranial fossa
portion of the internal base of the skull housing the frontal lobes
anterior horn (ventral horn)
gray matter
in the front of the spinal cord that contains
motor_neurons
Anton’s syndrome
form of
cortical blindness
in which the patient is unaware of/denies the visual
impairment
; due to a lesion of the occipital lobe extending from primary visual
cortex
into visual association
cortex
aphasia
syndrome of disordered expression or comprehension of spoken and/or written language caused by brain injury; see also
non-fluent
fluent
conduction
global
transcortical motor
and
transcortical sensory
aphasia
aphemia
inability to speak words despite being able to make other sounds and write
aphonia
complete loss of voice
apnea test
part of the “
brain death
exam”; verifies lack of responsiveness to carbon dioxide (paCO2 > 60 mm Hg) in the presence of respiratory acidosis (pH < 7.3)
apraxia
impaired planning/sequencing of movement that is not due to weakness, incoordination, or sensory loss. Although the movements cannot be performed for a specific situation, they may be performed under other circumstances (e.g., inability to lift feet off the floor when attempting to walk but preserved ability to perform bicycling movements of the legs while lying in bed). Results from dissociation of parts of the
cerebrum
and is often associated with parietal lobe lesions.
aprosencephaly
see
anencephaly
arachnoid
middle layer of the
meninges
covering the brain and spinal cord
arachnoid granulations
(arachnoid villi) branched tufts of
arachnoid
that project through the
dura mater
into the venous sinuses and function to return CSF to the systemic circulation
arachnoid villi
diverticula of the
arachnoid
mater in the
subarachnoid space
that extend into the veins and venous sinuses of the
dura
; a major pathway for the drainage of
cerebrospinal fluid
and transport across the endothelium into the blood.
arcuate fasciculus
pathway connecting Wernicke’s area in the posterior left superior temporal
gyrus
to Broca’s area in the left inferior frontal lobe; lesion results in impaired repetition
area postrema
chemoreceptor trigger zone for vomiting that is located on the
dorsal
surface of the
medulla
Argyll-Robertson pupil
pupil exhibiting
light-near dissociation
due to a lesion in the
midbrain
periaqueductal gray
matter caused by tertiary syphilis
Arnold-Chiari malformation
see
Chiari malformation
arousal
abrupt change from sleep to wakefulness, or from a “deeper” stage of
non-REM sleep
to a “lighter” stage
arteriovenous malformation
a tangled collection of abnormal arteries and veins
arteritis
inflammation of an artery
arthrokinetic nystagmus
nystagmus
induced by passive rotation of the arm of a stationary subject seated in total darkness inside a rotating drum
ascending tract of Deiters
direct pathway (lying just lateral to the
medial longitudinal fasciculus
) from the vestibular
nuclei
to the
ipsilateral
medial rectus subnucleus; clinical significance of this pathway is unclear
aseptic meningitis
syndrome characterized by headache, neck stiffness, low grade fever and
cerebro spinal fluid
lymphocytic pleocytosis in the absence of an acute bacterial pathogen; often used synonymously with viral
meningitis
, but also incudes meningeal inflammation due to various drugs (e.g., NSAIDs) or diagnostic procedures (e.g., angiography); atypical bacterial, fungal, parasitic, or
parameningeal
infection; neoplastic processes; and various systemic disorders
asomatognosia
inability to recognize part of one’s own body, seen with nondominant parietal lobe (or less commonly premotor cortex) lesions
associated reactions
movements of body parts other than the ones that are intended to move, often increased with increased effort
association cortex
cortical areas involved in higher order processing of sensory information and integration of multiple sensory and sensorimotor modalities
astasia
inability to stand because of motor incoordination
astasia-abasia
functional stance and gait characterized by bizarre movements, typically swaying wildly and nearly falling, but then recovering at the last minute
asterixis
sudden palmar flapping movement of the hands at the wrists; indicative of metabolic
encephalopathy
astrocytes
CNS
glia
that function to orient neuroblast migration in the cerebral and
cerebellar
hemispheres, provide mechanical support, react to injury, insulate synaptic surfaces, provide a source and sink for extracellular potassium and uptake neurotransmitters to terminate their synaptic action
astrocytoma
most common
central nervous system
tumor derived from
astrocytes
astrocytosis
reaction of
astrocytes
to neuronal injury characterized by an increase in the number and size of astrocytes (primary reaction) and cytoplasmic changes including increased glial filaments and glassy eosinophilic cytoplasm followed by formation of a dense gliotic scar (secondary reaction)
ataxia
incoordination of movement usually due to disease of
cerebellar
or sensory pathways
athetosis
involuntary, slow, writhing movements
atonia
loss of muscle tone
atonic seizure (drop attack)
generalized seizure
characterized by sudden loss of muscle tone and strength; may cause the head to drop suddenly, objects to fall from the hands or the legs to lose strength, with falling and potential injury
aura
warning symptom (e.g., of vision, smell or perception) occurring prior to a spell such as a
migraine
or
seizure
; implies focal brain disturbance
automatism
mechanical, seemingly aimless behavior (e.g., lip smacking or picking at clothes) characteristic of
complex partial seizures
autonomic
pertaining to the autonomic nervous system, which controls bodily functions that are not under conscious control (e.g., heartbeat, breathing, sweating)
autonomic nervous system
part of the
peripheral nervous system
that regulates visceral function and homeostasis independent of voluntary control
autoregulation
physiological process by which blood vessels change caliber to maintain constant cerebral blood flow over a wide range of
cerebral perfusion pressures
axial
transverse plane producing a cross-section of the body or head
axon
long, slender projection from the neruonal cell body that is specialized for the conduction of information encoded in the form of action potentials
axonal degeneration
neuropathic process resulting in degeneration of the
axon
and its
myelin
sheath; preferentially involves the distal portion of the
axon
(“dying back
neuropathy
“)
axonal spheroid
stereotypic
axonal
response to injury consisting of marked swelling due to accumulation of materials undergoing
axonal
transport
Babinski response
extension of the great toe on stimulation of the sole of the foot, signifying a lesion of the
corticospinal trac
t (a.k.a., upgoing toe); see also
plantar response
Balint syndrome
syndrome comprising
paralysis
of visual fixation, optic
ataxia
, and
impairment
of visual fixation due to bilateral lesions of the parietal and occipital lobes
basal ganglia
large
subcortical
nuclear masses consisting of the
caudate
putamen
globus pallidus
subthalamus
and
substantia nigra
; part of the motor system that permits chosen and inhibits unwanted movement
basal palisading
basal layer of small cells with darkly staining nuclei and little cytoplasm seen in the epithelium of
craniopharyngiomas
basilar artery
large
brainstem
artery located on the ventral surface of the
pons
formed by the joining of the two
vertebral arteries
and bifurcating into the
posterior cerebral arteries
; supplies blood to cerebral circulation and ventral
pons
basilar migraine
form of
migraine
characterized by a visual
aura
followed by an often occipital headache and one or more of the following symptoms:
dysarthria
vertigo
tinnitus
, decreased hearing,
diplopia
, blindness,
ataxia
, bilateral
paresthesia
, bilateral
paresis
and impaired cognition
behavioral symptom
complex changes in personality and behavior
Bell’s palsy (
idiopathic
facial
paralysis
cranial neuritis affecting the facial nerve thought to be due to reactivation of the herpes simplex virus; results in
lower motor neuron
facial weakness,
hyperacusis
, taste disturbance and impaired lacrimation
Bell’s phenomenon
fluttering of the eyes upward when closed eyelids are opened by the examiner
Benedikt syndrome
ipsilateral
oculomotor
palsy and
contralateral
hemichoreoathetosis due to lesion of the
ventral
midbrain
tegmentum
affecting the IIII nerve
fascicles
and the
red nucleus
Berry aneurysm
small
saccular aneurysm
of an intracranial artery
Binswanger’s disease (subcortical leukoencephalopathy)
degenerative
white matter
disease producing
dementia
due to hypertensive microvascular changes
lipohyalinosis
of the small arteries and
fibrinoid necrosis
of the larger vessels inside the brain)
blepharospasm
excessive involuntary contraction of the orbicularis oculi sometimes resulting in functional blindness; a focal
dystonia
blood-brain barrier
specialized system of capillary endothelial cells that strictly limits transport into the brain through both physical (tight junctions) and metabolic (enzymes) barriers
borderzone infarct
(aka watershed infarct)
infarct
occurring in tissue that is in the distalmost territory of two arteries and thus vulnerable to a reduction in blood supply; may be a result of global hypoperfusion or local atherosclerotic disease
brachial
relating to the arm
brachium
anatomical structure comprising a collection of
axons
that resemble an arm
brachium conjunctivum
see
superior cerebellar peduncle
brachium pontis
see
middle cerebellar peduncle
brachycephaly (acrocephaly)
premature fusion of bilateral coronal
sutures
producing a foreshortened skull
bradykinesia
slowed movement due to dysfunction of the
basal ganglia
and related structures
bradyphrenia
slowing of thought processes that can occur in
Parkinson disease
or as a side effect of antipsychotic medications
brain death
see
death by neurological criteria
brainstem
medulla
pons
and
midbrain
brainstem auditory evoked potentials (BAEP)
series of waves that reflect sequential activation of neural structures along the auditory pathways following a brief click or tone transmitted via an earphone or headphone and measured by surface electrodes placed at the vertex of the scalp and ear lobes; provides information regarding auditory function and hearing sensitivity and used to screen for retrocochlear pathology (e.g., acoustic
neuroma
), universal newborn hearing screening and intraoperative monitoring
brain death
see
death by neurological criteria
Broca’s aphasia
see
non-fluent aphasia
Brodmann’s areas
distinct regions of the
cerebral cortex
recognized by variations in cell size, density and thickness of the cortical layers
Brown Sequard syndrome
spinal cord injury syndrome associated with damage to one lateral half of the spinal cord (spinal hemisection) resulting in
ipsilateral
weakness and loss of vibration
proprioception
and
contralateral
loss of pain sensation
Brudzinski’s sign
involuntary flexion of the hips in response to passive flexion of the neck; indicative of
meningeal
irritation
bruxism
grinding one’s teeth while asleep
bulbar
pertaining to the lower cranial nerve
nuclei
in the lower (pons and medulla) brainstem (“bulb” is an archaic term for medulla)
burst fracture
compression fracture of vertebral body with expansion in sagittal and coronal planes due to axial loading; unstable and often associated with spinal cord injury
calcarine cortex
primary visual
cortex
located in the occipital lobe (striate area 17)
carotid sinus
arterial baroreceptor located at the bifurcation of the external and internal carotid arteries that regulates arterial pressure and heart rate in response to changes in stretch and transmural pressure
carphologia
see
floccillation
catamenial
referring to menses; with regard to women with
epilepsy
or
migraine
, a tendency for
seizures
/migraines to occur around the time of menses
cataplexy
sudden loss of postural tone, often triggered by an emotional stimulus and resulting in falls to the floor; seen in
narcolepsy
cauda equina
(“horse’s tail”) collection of intradural spinal nerve roots
caudal
to the spinal cord that supply the lower limbs and pelvis; since this structure is part of the
peripheral nervous system
, lesions produce
lower motor neuron
deficits
caudal
toward the tail
caudate
portion of the
basal ganglia
that lies in the floor of the lateral ventricle
cavernoma (cavernous malformation)
vascular malformations composed primarily of large venous channels without a clear-cut arterial component
cavernous sinus
paired, venous structures located on either side of the
sella turcica
that receive blood from the superior and inferior orbital veins and drain into the superior and inferior petrosal sinuses; contains the
carotid artery
and its sympathetic plexus, the oculomotor nerves (III, IV, VI) and the ophthalmic branch of V; lesions typically result in
ophthalmoplegia
, orbital congestion and
proptosis
central chromatolysis
regenerative response to
axonal
injury consisting of
neuronal
swelling, nuclear eccentricity and loss of Nissl substance
central cord syndrome
spinal cord injury syndrome associated with damage to the central portion of the spinal cord characterized by bilateral weakness of distal>proximal muscles in the arm>leg, bladder dysfunction, and a variable degree of sensory loss below the level of injury
central herniation
downward displacement of the
cerebral hemispheres
pushing the
diencephalon
and
midbrain
through the tentorial notch; symptoms classically follow a rostrocaudal deterioration
central nervous system (
CNS
brain and spinal cord
central pain syndrome
intense pain arising from injury to the
central nervous system
, most often in patients who have had a
stroke
multiple sclerosis
or brain injury.
central sulcus
prominent sulcus on the dorsolateral aspect of the
cerebral hemispheres
formed by the precentral and postcentral
gyri
; defines the boundary between the frontal and parietal lobes
centrum semiovale
expansive region of
white matter
in the dorsal core of the frontal and parietal lobes, named because of its central position in the
forebrain
and its semi-oval shape
cephalic
relating to the head
cerebellar peduncle
three major
white matter
structures containing
efferent
and
afferent
axons
of the
cerebellum
; named the inferior, middle and superior
cerebellar
peduncles
cerebellar tonsil
lateral portions of the uvula located in the posterior lobe of the
cerebellum
cerebellopontine angle
space located at the junction of the
cerebellum
pons
, and
medulla
containing cranial nerves V-XI, blood vessels, the
flocculus
of the cerebellum and choroid plexus
cerebellum
brain structure in
posterior fossa
that coordinates the many muscles active in any given movement; receives input from spinal cord and
cerebral cortex
and projects to postural and voluntary motor control systems and
red nucleus
cerebral amyloid angiopathy (congophilic angiopathy)
vascular disorder in which beta amyloid protein is deposited within the media and adventitia of small- to medium-sized meningeal and
cortical
blood vessels, causing them to become brittle and break; important cause of predominantly lobar intracerebral hemorrhage in the elderly
cerebral aqueduct
portion of the ventricular system that lies in the dorsal
midbrain
and connects the third and fourth ventricles
cerebral arteriosclerosis
thickening and hardening of the arteries within the brain
cerebral atherosclerosis
build-up of fatty deposits in the inner wall of cerebral arteries; form of
cerebral arteriosclerosis
cerebral atrophy
the shrinking of the brain or brain cells.
cerebral autosomal dominant arteriopathy with
subcortical
infarcts
& leukoencephalopathy (CADASIL)
familial arterial disease of the brain caused by mutations in the Notch3 gene and consisting of recurrent
subcortical
strokes
starting in midadult life,
dementia
, depression and
migraine
cerebral cortex
highly convoluted layer of
gray matter
that constitutes the outermost layer of the
cerebrum
and is responsible for integrating sensory impulses and for higher intellectual functions
cerebral hemisphere
symmetrical half of the
cerebrum
as separated by the
sagittal sulcus
and containing the
cerebral cortex
basal ganglia
hippocampus
and
amygdala
cerebral peduncle (crus cerebri)
white matter
tracts (
corticospinal
and
corticobulbar
) on the ventral surface of the
midbrain
containing the
efferent
axons
of
cerebral cortex
that project to
brainstem
and spinal cord
cerebral perfusion pressure (CPP)
mean arterial pressure (MAP) – intracranial pressure (ICP)
cerebral salt wasting
centrally-mediated hypovolemic hyponatremia associated with negative sodium balance that occurs in approximately 30-50% of patients with
subarachnoid hemorrhage
despite their being given maintenance volumes of fluids; excessive sodium loss is thought to be due to impaired sodium reabsorption in the proximal tubule and may be caused by disruption of sympathetic input to the kidneys, production of a circulating natriuretic factor or both
cerebritis
inflammation of the brain
cerebrospinal fluid (CSF)
clear, colorless fluid bathing the entire surface of the
CNS
, most of which is secreted by the
choroid plexus
and the remainder by brain capillaries; flows through the ventricles and out into the
subarachnoid space
via the foramen of Magendie in the midline and the two foramina of Luschka at the lateral margins of the roof of the 4th ventricle, then is absorbed through the
arachnoid villi
in the walls of
dura
l sinuses and returned to the systemic circulation
cerebrum
anterior portion of the brain consisting of the two
cerebral hemispheres
that each contain four lobes
Charcot-Bouchard aneurysm
aneurysmal dilation of small intraparenchymal vessels commonly seen in the brains of patients with
hypertensive hemorrhage
Charcot joint
progressive destruction and deformity of bone and soft tissue at weight bearing joints due to severe sensory or autonomic
neuropathy
cheiro
relating to the hand
Chiari malformation
CNS
disorder characterized by
cerebellar
elongation and protrusion through the foramen magnum into the cervical spinal cord. Type I consists of
caudal
displacement of the
medulla
and inferior pole of the
cerebellar
hemispheres through the foramen magnum. Type II=type I +
hydrocephalus
and lumbosacral
spina bifida
. Type III involves herniation of the entire
cerebellum
through the foramen magnum with a cervical
spina bifida
cystica. Type IV involves
cerebellar
hypoplasia
chorea
involuntary, irregular, rapid, jerking movements
choroid plexus
intraventricular structure that secretes
cerebrospinal fluid
choroid plexus papilloma
histologically benign intracranial tumor of neuroectodermal origin that is most commonly located in a
ventricle
(lateral>fourth>third), where it often presents with
non-communicating hydrocephalus
due to overproduction of
CSF
; may also be seen in the
cerebellopontine angle
chronic daily headache
headache disorder consisting of frequent headache occurring 15 or more days per month and including headache associated with medication overuse
chronic paroxysmal hemicrania
indomethacin-responsive headache
disorder characterized by the occurrence of multiple daily attacks lasting 5 to 30 minutes of severe unilateral head pain often associated with
autonomic
phenomenon (eye tearing, eye redness, eyelid edema, nasal congestion, runny nose); also known as atypical
cluster headache
chronic-progressive
developing over months to years; implies gradual deterioration as occurs with degenerative diseases like
Alzheimer disease
Huntington disease
, etc.
cingulate gyrus
cortical
component of the
limbic
system located on the medial aspect of the hemisphere superior to the
corpus callosum
; involved in emotional and cognitive processing
cingulate herniation
horizontal displacement of a
cerebral hemisphere
due to an expanding lesion that forces the
cingulate gyrus
under the
falx cerebri,
compressing the internal cerebral vein and the
contralateral
hemisphere
circadian rhythm
innate daily fluctuation of physiological or behavioral functions, including sleep-wake states generally tied to the 24-hour daily dark-light cycle
Circle of Willis
the main arterial anastomatic trunk located at the base of the brain; place where the two
internal carotid arteries
and the
basilar
artery come together, allowing blood to be redistributed to the
anterior
middle
and
posterior
cerebral arteries
“clasp knife”
spring-like resistance to passive extension at the elbow or flexion at the knee that increases up to a certain length and force before suddenly relaxing as the
Golgi tendon organ
is activated; sign of
spasticity
classic migraine
see
migraine with aura
Claude Syndrome
ipsilateral
oculomotor
palsy and
contralateral
ataxia
and hemichoreoathetosis due to a
dorsal
midbrain
tegmental
lesion affecting the III nerve
fascicles
superior cerebellar peduncle
and
red nucleus
claustrum
thin plate of
gray matter
lying in the
white matter
between the
insula
and the
basal ganglia
that modulates
cortical
activity
clay shoveler’s fracture
typically stable fracture through a spinous process due to hyperextension injury
clonic seizure
generalized seizure
characterized by jerking movements on both sides of the body
clonus
rhythmic contraction relaxation
tremor
due to cyclic alternations of the spindle stretch reflex and the
Golgi tendon organ
reflex; indicative of exaggerated
stretch reflexes
cluster headache
primary headache syndrome characterized by intense, unilateral orbital, supraorbital, and/or temporal pain lasting 15-180 minutes and occurring in “clusters” up to several times per day for a period of one or more months before going into “remission” for months or years; diagnosis requires one or more of the following
autonomic
abnormalities
ipsilateral
to the headache: conjunctival injection, lacrimation,
ptosis
miosis
, eyelid edema, nasal congestion, rhinorrhea or facial sweating
CNS
central nervous system
CNS metastasis
metastatic tumors typically spread by a hematogenous route and found at the junction between
gray matter
and
white matter
where they are trapped by the acute angle branching of the microvasculature
cogwheeling
ratchety movement due to superimposition of
tremor
on
rigidity
coital headache
indomethacin-responsive headache
disorder characterized by sudden, severe, throbbing, occipital headache that occurs just before or during orgasm
cold calorics
see
oculovestibular response
coma
state of unarousable unresponsiveness with closed eyes, no speech and no purposeful movements
common carotid artery
artery that arises from the brachiocephalic artery on the right and from the aortic arch on the left, ascending in the neck and dividing at the upper border of the thyroid cartilage into the external and
internal carotid arteries
to supply the head and neck
common migraine
see
migraine without aura
communicating hydrocephalus
blockage of
CSF
flow outside the ventricular system, either at the level of the
arachnoid granulations
or because of overproduction of CSF (e.g., from a
choroid plexus papilloma
) that exceeds the rate of absorption
complex partial seizure
partial seizure
in which consciousness or awareness is impaired; epileptic discharge either originates in
limbic
structures (
hippocampus
) or spreads to them from neo
cortex
, especially from the frontal lobe
complex tic
distinct, coordinated patterns of successive movements involving several muscle groups; complex vocal
tics
include meaningful syllables, words or phrases; complex motor tics are coordinated or sequential patterns of movement such as twirling a pencil or touching other people
concussion
traumatic closed head injury that results in temporary impairment of neurological function, e.g., transient loss of consciousness
conduction aphasia
selective impairment of the ability to repeat due to a lesion of the
arcuate fasciculus
, which connects Wernicke’s area to Broca’s area
conduction block
failure of impulse conduction along an anatomically intact
axon
; characteristic of
demyelinating
neuropathy
contracoup
opposite to the site of impact
contracture
permanent shortening of the muscles and tendons adjacent to a joint, which can result from severe
spasticity
and interferes with normal movement around the affected joint
contralateral
located on the opposite side of the body (brain)
contusion
edematous brain lesion containing punctuate
parenchymal
hemorrhages on the surface of the brain that may extend bidirectionally into the
white matter
and the
subdural
and
subarachnoid spaces
; occur at the site of impact (
coup
contusion) with direct trauma and at a site opposite to the site of impact (
contracoup
contusion) with acceleration/deceleration injury
conus medullaris
caudal
-most part of the spinal cord located between the first and second lumbar vertebrae. Since this structure is part of the spinal cord but is in close proximity to spinal nerve roots, lesions often produce both
upper motor neuron
and
lower motor neuron
deficits
convergence
coordinated inward movement of the eyes in order to fixate on a near object
convergence-retraction nystagmus
form of
nystagmus
consisting of jerking eye movements inward and backward; associated with dorsal
midbrain
lesion
conversion disorder (functional neurological symptom disorder)
somatoform disorder involving physical symptoms or signs that cannot be explained by an organic neurological or medical condition; term derives from the historical belief that the disorder involves conversion of psychological distress into neurological symptoms, but new criteria do not require presence of a psychological stressor
coprolalia
uncontrolled, often obsessive use of obscene language occasionally seen in
Tourette syndrome
coronal
vertical plane from head to foot and parallel to the shoulders
corona radiata
fan-like arrangement of fibers projecting from all aspects of the
cerebral cortex
and converging toward the
thalamus
where they will form the
internal capsule
corpus callosum
large fiber structure that makes connections between homotopic regions of the
cerebral hemispheres
; bend at its anterior limit is called the
genu
; bend at its
caudal
end is called the
splenium
; portion between the two is called the body.
corpus striatum
(“striped body”) part of the
basal ganglia
consisting of the
caudate
putamen
and
globus pallidus
cortical
referring to the
cerebral cortex
, the outermost layer of the
cerebrum
cortical blindness
apparent lack of visual functioning in spite of anatomically and structurally intact eyes due to bilateral lesions of the primary visual
cortex
corticobasal degeneration
progressive neurological disorder characterized by nerve cell loss in the
cerebral cortex
and
basal ganglia
and producing
parkinsonism
dementia
, visual-spatial impairment,
alien hand syndrome
apraxia
and
myoclonus
corticobulbar tract
axons
originating in the posterior frontal lobe and projecting to
lower motor neurons
of the cranial nerves in the lower
brainstem
(“bulb” is an archaic term for medulla)
corticospinal tract (pyramidal tract)
motor pathway responsible for voluntary movement that arises from primary motor
cortex
, area 6 and somatosensory
cortex
and descends through the
corona radiata
internal capsule
cerebral peduncle
, medullary
pyramid
(where it decussates) and spinal cord to
alpha motor neurons
in spinal cord
gray matter
cough headache
indomethacin-responsive headache
disorder characterized by transient, severe, explosive head pain upon coughing, sneezing, weight lifting, bending or stooping
coup
lesion at the site of impact
Cowdry A inclusion bodies
eosinophilic nuclear inclusions surrounded by a clear halo in neurons or glial cells occurring in herpes simplex
encephalitis
Cowdry B inclusion bodies
large glassy eosinophilic nuclear inclusions occurring in herpes simplex
encephalitis
craft palsy
dystonia
occurring in the setting of a highly learned skilled task, e.g., writer’s cramp, yips in golfers
craniectomy
surgical removal of a section of bone (bone flap) from the skull for the purpose of operating on the underlying tissues or relieving intracranial pressure, in which the bone flap is not replaced at the end of the procedure
craniopharyngioma
suprasellar
WHO
grade I tumor of children/young adults that causes significant morbidity and mortality; characterized histologically by basal palisading, wet keratin and infiltrative fingers of tumor that make it difficult to cure
cranioplasty
surgical repair of a defect or deformity of the skull; replacement of a bone flap
craniorachischisis totalis
fatal neural tube defect consisting of total failure of
neurulation
; a neural plate-like structure is entirely exposed without overlying bony or dermal covering
craniosynostosis
premature closure at birth of one or more cranial
sutures
, which limits head growth perpendicular to the
suture(s)
; see also
brachycephaly
oxycephaly
plagiocephaly
scaphocephaly
trigonocephaly
craniotomy
surgical removal of a section of bone (bone flap) from the skull for the purpose of operating on the underlying tissues, in which the bone flap is replaced at the end of the procedure
creatine kinase
enzyme that catalyzes the conversion of creatine to phosphocreatine and is released into the blood by tissues — particularly muscle — that consume adenosine triphosphate (ATP) rapidly; elevated levels are seen in
myopathy
cremasteric reflex
superficial (cutaneous) reflex elicited by stroking the superior and medial part of the thigh in a downward direction; normal response is contraction of the cremasteric muscle that pulls up the scrotum and testis on the side stroked; dependent on nerve roots L1 and L2
Creutzfeldt-Jakob disease
fatal
prion
disease characterized by spongiform changes in the brain, progressive
dementia
, psychiatric changes and
myoclonus;
form of
spongiform encephalopathy
crossed adductor reflex
reflex contraction of the adductor magnus caused by tapping the opposite knee; indication of hyperreflexia on the side of the adductor contraction; commonly thought to be due to stimulation of the adductor muscle on the hyperreflexive side through slight jarring of the pelvis
“crossed signs”
ipsilateral
cranial nerve signs and
contralateral
long-tract signs
: implies lesion of the
brainstem
; sometimes used synonymously with
dissociated sensory deficits
due to spinal cord or brainstem lesions
crural
relating to the leg
crus cerebri
see
cerebral peduncle
cryptogenic
occurring without known cause; in the context of
epilepsy
, indicates cases in which a lesion and distinct pathogenesis are presumed
cyclopia
central orbit located in the middle of the face due to fusion of the eyes associated with
holoprosencephaly
cyclotorsion
(a.k.a. torsion): rotation of the eye around an anterior-posterior axis; see
excyclotorsion
incyclotorsion
Dawson’s fingers
ovoid
demyelinating
lesions with their long axis perpendicular to the ventricular surface seen in
multiple sclerosis
death by neurological criteria
irreversible loss of all brain function
decerebrate rigidity
stereotyped posture consisting of extension of all four limbs occurring with transaction between the
superior collicui
and
inferior colliculi
in the
midbrain
; often used synonymously with
extensor posturing
decorticate rigidity
stereotyped posture consisting of flexion of the forelimbs and extension of the hindlimbs occurring with transaction between the
diencephalon
and
midbrain
; often used synonymously with
flexor posturing
decussate
to cross
deja vu
feeling as if one has lived through or experienced this moment before; may occur in people without any medical problems or as a
seizure
aura
delayed sleep phase syndrome
circadian rhythm
disorder in which in the daily sleep/wake cycle is delayed with respect to clock time such that sleep occurs well after the conventional bedtime; common in young adults
delirium
abnormal mental state characterized by disorientation, inattention, confusion, fear, irritability, perceptual disturbance, and fluctuating level of consciousness; common with toxic and metabolic disorders and acute febrile systemic infections
dementia
acquired and sustained loss of memory and other intellectual functions that is of sufficient severity to interfere with daily functioning
dementia pugilistica
chronic traumatic
encephalopathy
caused by cumulative and repetitive head trauma and manifesting as
dementia
and
parkinsonism
demyelination
destruction or loss of the myelin sheath surrounding
axons
; results in impaired nerve impulse conduction
dendrite
receiving portion of the
neuron
denervation
loss of nerve supply
dermatome
distribution of sensory innervation on the skin of the body and the limbs
diabetes insipidus
inability to concentrate urine resulting from decreased secretion of antidiuretic hormone; reflects a lesion of the
hypothalamic
osmoreceptors, supraoptic or paraventricular
nuclei
, or the supraopticohypophyseal tract and may occur in
transtentorial herniation
due to downward traction on the
hypothalamic
median eminence
diaphragma sellae
thin
dural
membrane overlying the
sella turcica
that is fenestrated to allow passage of the
infundibulum
diaschisis
depression of metabolism at sites distant from, but connected with, a site of cerebral injury (e.g.,
infarction
) due to interruption of
afferent
or
efferent
fiber pathways
diastematomyelia
longitudinal division of the spinal cord by a septum of bone
diencephalon
thalamus
hypothalamus
subthalamic nucleus
and
pineal
diffuse axonal injury
widespread damage to
white matter
due to rotational shearing forces with head trauma
diffuse Lewy body disease (Lewy body dementia)
form of
dementia
associated with fluctuating alertness, recurrent visual hallucinations and
parkinsonism
and defined pathologically by
cortical
(as well as nigral)
Lewy bodies
diplegia
see
paraplegia
diplopia
double vision
dissociated sensory deficit
impairment
of pain/temperature sensation with preservation of vibration/
proprioception
or vice versa; implies lesion of
brainstem
or spinal cord involving 1 sensory tract but sparing the other
dolichocephaly
see
scaphocephaly
doll’s phenomenon
see
oculocephalic response
dorsal
posterior
dorsal columns
ascending
axonal
tract running in the dorsal funiculus of the spinal cord that carries tactile and
proprioceptive
information to the brain; fibers cross in the ventromedial
medulla
to become the
medial lemniscus
dorsal horn
see
posterior horn
dorsal motor nucleus of the vagus
parasympathetic nucleus that stimulates secretion from glands of the pharynx and thoracic and abdominal viscera
dorsal rhizotomy
surgical procedure involving sectioning of the dorsal spinal nerve roots performed to reduce
spasticity
dorsal root ganglion
collection of cell bodies located in the intervertebral foramina that transduce sensory information into neural signals and transmit these signals to the
CNS
dose failure
phenomenon in which an individual dose of medication has no effect; occurs in
Parkinson disease
possibly in association with a tablet getting stuck in the throat or delayed gastric emptying
double simultaneous stimulation (DSS)
ability to detect two stimuli applied simultaneously to opposite sides of the body; for tactile DSS, if a patient is able to identify which side is being touched when each side is touched individually, but extinguishes or neglects one of the sides when both sides are touched simultaneously; indicates dysfunction of the
contralateral posterior
parietal lobe
drop metastases
tumor masses in the lumbosacral spinal cord due to
CSF
spread of neoplastic cells (e.g.,
medulloblastoma
duction
movement of one eye
dura mater
outermost layer of the
meninges
covering the brain and spinal cord; consists of a thick fibrous tissue that is adherent to the inner table of the skull and forms a protective sheath in the vertebral canal
dural tail sign
tail of
dural
enhancement seen on CT or MRI in association with meningeal neoplasms such as
meningioma
Duret hemorrhages
secondary hemorrhages occurring in the
diencephalon
midbrain
, and
pons
as downward movement of the
brainstem
relative to the immobile blood vessels on the surface of the brainstem results in injury to small penetrating blood vessels; sequelae of cerebral herniation
dysarthria
inability to pronounce or articulate words due to weakness or incoordination of the vocal apparatus (e.g., lips, tongue, larynx)
dysdiadochokinesia
impaired ability to perform rapid alternating movements (e.g., pronation/supination of hands); indicates
cerebellar
dysfunction
dysesthesia
pain or discomfort in response to a stimulus (e.g., touch) that would not be expected to cause pain
dysgeusia
distorted taste perception
dysgraphia
a writing disability that results in incorrectly spelled or written words
dyskinesia
blanket term for movement disorders characterized by increased motor activity
dyslexia
disorder that limits the ability to read
dysmetria
difficulty judging and controlling the speed, distance, or power of motor actions; tendency to over- or underestimate the extent of motion needed
dysphagia
difficulty in swallowing
dysphonia
voice disorder, often related to weakness of laryngeal muscles, in which sound production is impaired
dysraphism
defective closure of a
raphe
, particularly the
neural tube
dyssomnia
disorder in which the main complaint is about inadequate or unrefreshing sleep
dystonia
involuntary muscle spasms that produce peculiar postures of different body parts
echolalia
imitation of sounds without comprehension of their meaning
echopraxia
imitative repetition of the movements, gestures or posture of another person occasionally seen in
Tourette syndrome
Edinger-Westphal nucleus
accessory nucleus of each oculomotor nerve that supplies preganglionic parasympathetic fibers for pupillary constriction and lens
accommodation
; located in the midline between the extraocular oculomotor nerve nuclei
efferent
motor pathway proceeding from the
CNS
toward the peripheral end organs
electromyography
graphical representation of the electrical activity in a muscle
eidetic memory (photographic memory)
ability to vividly recall visual images, sounds, or objects in memory with extraordinary detail
electroencephalogram (EEG)
system for recording the electrical potentials of the brain derived from electrodes attached to the scalp
eloquent cortex
regions of the
cerebral cortex
responsible for motor, sensory, language or other cognitive processing that if removed, will result in a neurological deficit; identification of eloquent cortex through brain mapping is a vital part of the planning for epilepsy surgery and resection of brain tumors and vascular malformations in order to minimize adverse outcomes from surgery
empty sella
downward displacement and compression of the
pituitary gland
by
cerebrospinal fluid
filling the
sella turcica
; primary empty sella syndrome occurs when a small defect in the
diaphragma sellae
increases pressure in the sella and compresses the
pituitary
; secondary empty sella syndrome occurs when the sella is empty because the
pituitary
has shrunken following injury, surgery or radiation
encephalitis
inflammation of brain tissue
encephalocele
failure of bone fusion in the posterior midline of the skull resulting in a bony cleft through which
meninges
and/or brain
parenchyma
protrude encephalomalacia focal softening of the brain in areas of tissue death following cerebral
infarction
, infection, trauma, etc.
encephalopathy
literally, “brain suffering”; diffuse brain dysfunction that may be caused by toxins, infection, metabolic or mitochondrial disease, tumor or increased intracranial pressure, trauma or lack of blood flow or oxygen to the brain; the hallmark is impaired level of consciousness
endomysium
innermost layer of connective tissue that forms an interstitial layer around each individual muscle fiber
endoneurium
(epilemma) innermost layer of connective tissue of a peripheral nerve that forms an interstitial layer around each individual
axon
Schwann cell
unit
enophthalmos
recession of the eyeball within the orbit
eosinophilic neuronal necrosis
neuronal
response to
ischemia
and
hypoxia
characterized by brightly eosinophilic (red) cytoplasm and nuclear shrinkage
ependyma
epithelial lining of the ventricles of the brain and the canal of the spinal cord
ependymal cells
type of
glia
consisting of cuboidal cells lining the adult ventricles and spinal canal
ependymal true rosette
halo of cells surrounding an empty lumen; fairly specific for, though infrequently seen in,
ependymomas
ependymoma
WHO
grade II primary
CNS
tumor of children (involving the 4th ventricle) and young adults (involving the spinal cord); characterized histologically by perivascular pseudorosettes, ependymal true rosettes, sharp demarcation and enhancement on CT/MRI
ephaptic
electrical conduction of a nerve impulse across a non-synaptic contact site between nerves and without the mediation of a neurotransmitter
epilepsy
chronic brain disorder of various etiologies characterized by recurrent unprovoked
seizures
epilepsy syndrome
disorder defined by
seizure
type, clinical and
EEG
findings, age of onset, family history, response to therapy, and prognosis epineurium outermost layer of a peripheral nerve containing connective tissue and an anastomotic vascular network
epithalamus
dorsal posterior subdivision of the
diencephalon
generally considered to include the
habenula
, the
pineal
body and the epithelial roof of the third ventricle
esotropia
an eye with
strabismus
that deviates inward
essential tremor
medium or high frequency (4-8 Hz)
tremor
that occurs with action or holding a sustained posture that typically affects the arms, the head/neck or the voice
evoked potentials
recordings of the nervous system’s electrical response to the stimulation of specific sensory pathways; see also
somatosensory evoked potentials
brainstem auditory evoked potentials
and
visual evoked potentials
excessive daytime sleepiness (hypersomnolence)
subjective difficulty in staying awake and easily falling asleep when sedentary
excyclotorsion
(a.k.a. extorsion):
cyclotorsion
of an eye such that the superior pole rotates outward
executive functions
higher intellectual functions such as judgment, insight, reasoning, abstraction
exophthalmos
see
proptosis
exotropia
an eye with
strabismus
that deviates outward
Expanded Disability Status Scale (EDSS)
20-point scale, ranging from 0 (normal examination) to 10 (death) by half-points, that measures
impairment
(gait is heavily emphasized); used in clinical trials of
multiple sclerosis
extensor plantar response
extension of the great toe (“upgoing toe”) with fanning of the other toes in response to application of a stimulus to the skin of the foot or leg; signifies a lesion of the
corticospinal tract
extensor posturing
stereotyped posture occurring in
coma
in response to stimulation in which the arms and legs extend (hips and shoulders extend, adduct, and internally rotate; knees and elbows extend; forearms hyperpronate; wrists and fingers flex; feet plantarflex and invert; and trunk extends); reflects “release” of primitive responses from the suppression of more
rostral
motor areas that have been damaged and is reminiscent of the decerebrate state demonstrated in animals with transection through the
midbrain
colliculi
extensor response in the arm
stereotyped posture occurring in
coma
in response to stimulation in which the upper extremity extends (shoulder extends, adducts, and internally rotates; elbow extends; forearm hyperpronates; wrist and fingers flex); may be accompanied by extension of the lower extremity (hip extends, adducts, and internally rotates; knee extends; foot plantar flexes and inverts) as in
decerebrate rigidity
; reflects “release” of primitive responses from the suppression of more
rostral
motor areas that have been damaged
extensor spasm
manifestation of
spasticity
in which the legs involuntarily straighten into an extended position where they remain for several minutes
extinction
see
double simultaneous stimulation
extra-axial
within the skull or vertebral column but outside of the brain or spinal cord
extrapyramidal
movement disorder not involving the
corticospinal tracts
; typically refers to
basal ganglia
or
cerebellar
disorders
extrasylvian
outside of the area surrounding the
Sylvian fissure
; often used synonymously with “transcortical,” as in
transcortical motor aphasia
and
transcortical sensory aphasia
F-wave
long latency muscle action potential seen after supramaximal stimulation to a nerve
facial masking (hypomimia)
decreased facial expression due to
rigidity
of facial muscles
facial nerve (cranial nerve VII)
predominantly motor nerve supplying muscles of facial expression; also carries sensation (external ear, taste from anterior 2/3 of tongue) via the nervus intermedius and preganglionic
parasympathetic
fibers to the lacrimal, palatal and nasal glands
fainting
see
syncope
falx cerebri
fold of
dura
mater in the
sagittal sulcus
between the two
cerebral hemispheres
fascicle
bundle of
axons
(nerve fascicle) or muscle fibers (muscle fascicle) surrounded by a layer of contractile cells (
perineurium
for nerves or
perimusium
for muscles)
fasciculation
spontaneous firing of an
axon
resulting in a visible twitch of all the muscle fibers it contacts; indicative of denervation
febrile seizure
typically benign
seizure
associated with high fever in children aged 3 months to 5 years
festination
an involuntary tendency to take short accelerating steps in walking that can occur in
Parkinson disease
fibrillation
spontaneous firing of a single muscle fiber not visible to the naked eye, indicative of denervation or irritable
myopathy
; seen electrographically as a brief action potential with initial positive (down) wave followed by negative (up) wave
fibrinoid necrosis
brightly eosinophilic lesions in the small vessels of the brain postulated to occur because of disordered cerebral
autoregulation
in association with aging and hypertension; contributes to the development of
lacunar infarction
and
hypertensive hemorrhage
filum terminale
fibrous tissue extension of the
spinal cord
from the
conus medullaris
to the coccyx; surrounded by
cauda equina
finger agnosia
type of
agnosia
characterized by inability to identify the fingers; a component of
Gerstmann syndrome
Fisher scale
scale for grading CT appearance in patients with nontraumatic
subarachnoid hemorrhage
; higher scores predictive of developing symptomatic cerebral
vasospasm
Description
Grade
No subarachnoid blood detected
Diffuse subarachnoid blood or vertical layers of blood < 1 mm thick
Localized clots and/or vertical layers of blood < 1 mm thick
Intracerebral or intraventricular clots with diffuse or no subarachnoid blood
flaccidity
severe form of
hypotonicity
flexor plantar response
flexion (curling down) of all toes (“downgoing toe”) in response to application of a stimulus to the skin of the foot or leg; normal response
flexor posturing
stereotyped posture occurring in
coma
in response to stimulation in which the upper extremity flexes and the lower extremity extends; reflects release of primitive responses from the suppression of more
rostral
motor areas that have been damaged and is reminiscent of the
decorticate
state demonstrated in animals with transaction of corticospinal fibers above the midbrain
flexor response in the arm
stereotyped posture occurring in
coma
in response to stimulation in which the upper extremity flexes and the lower extremity extends; reflects release of primitive responses from the suppression of more rostral motor areas that have been damaged and is reminiscent of the decorticate state demonstrated in animals with transaction of corticospinal fibers above the midbrain
flexor spasm
often painful manifestation of
spasticity
in which the legs involuntarily pull upward into a clenched position for a period of a few seconds
floccillation
purposeless picking at clothing or bedding seen in
delirium
flocculus
small lobe of the posterior
cerebellum
; comprises the lateral portion of the vestibulocerebellum
fluent aphasia (Wernicke’s or receptive aphasia)
impairment of language comprehension including impaired repetition due to lesion of the posterior left superior temporal
gyrus
Brodmann area
22)
Foix-Chavany-Marie phenomenon
loss of voluntary control of facio-pharyngo-glosso-masticatory muscles (resulting in anarthria, dysphagia, and absent mouth movements) due to bilateral lesions of the frontal operculum or the cortical-subcortical areas of primary motor cortex
fontanel
soft membranous gap between the incompletely formed cranial bones of a fetus or an infant; the anterior fontanel (where the metopic, the two coronal, and the sagittal
sutures
come together), fuses at 7-19 months; the posterior fontanel (where the lambdoid and
sagittal sutures
come together) is often fused at birth
foramen magnum
large opening at the base of the skull through which the spinal cord and
vertebral arteries
pass from the vertebral cavity into the cranial cavity
foramen of Magendie
midline exit of
CSF
from the fourth
ventricle
into the
subarachnoid space
foramen of Monro
permits communication of the third
ventricle
with each of the lateral ventricles on anterolateral aspect of the third ventricle
foramina of Luschka
lateral exits of
CSF
from either side of the fourth
ventricles
into the
subarachnoid space
forebrain
portion of the
central nervous system
derived from
prosencephalon
; commonly used to denote
cerebral hemispheres
and
diencephalon
fornix
white matter
structure containing
axons
that connect the
hippocampus
to the
hypothalamus
and septal
nuclei
fortification spectrum (teichopsia)
complex visual
migraine aura
consisting of zig-zag lines or an arc of scintillating lights forming into a herringbone pattern and expanding to encompass an increasing portion of a visual hemifield
Foster-Kennedy syndrome
ipsilateral
anosmia
, ipsilateral
optic atrophy
and
contralateral
papilledema
due to frontal lobe or olfactory groove mass lesion
fovea
center most part of the
macula
responsible for detailed central vision
Foville syndrome
ipsilateral
lateral gaze palsy, ipsilateral peripheral facial palsy, and
contralateral
hemiplegia
due to a
dorsal
pontine
tegmentum
lesion affecting the
paramedian pontine reticular formation
facial nerve
nucleus
or
fascicle
and
corticospinal tract
fracture-dislocation
fracture through the articular processes and disc with or without associated fracture through a vertebral body due to flexion/extension with axial loading; unstable and often associated with spinal cord injury
freezing
sudden, brief cessation of movement; common in
Parkinson disease
Fresnel prisms
clear, flexible polyvinyl chloride plastic sheets composed of a series of small prisms that are used to assess and correct
diplopia
fried egg artifact
perinuclear halo around
oligodendrocytes
caused by formalin fixation artifact Friedreich’s ataxia autosomal recessive neurodegenerative disease caused by GAA triplet repeat mutation in the gene that encodes for frataxin, a protein that regulates mitochondrial functioning; characterized by weakness,
ataxia
, sensory loss, scoliosis and cardiomyopathy
frontal eye fields (FEF)
region within the frontal lobes from which voluntary lateral eye movements originate; with stimulation (as in
seizure
), the eyes move conjugately to the opposite side; with destruction (as in a
stroke
), the eyes look towards the lesioned side (loss of controversion), implying unopposed stimulation from the undamaged side
frontotemporal dementia
group of
dementing
illnesses in which disordered behavior (e.g., disinhibition) or language (e.g.,
aphasia
) are disproportionately impaired in relation to memory; includes
Pick’s disease
and
corticobasal degeneration
functional
not due to organic disease
functional neurological symptom disorder (conversion disorder)
somatoform disorder involving physical symptoms or signs that cannot be explained by an organic neurological or medical condition
funiculus
see
tract
gadolinium-enhancing lesion
abnormality on MRI that becomes bright after injection of the chemical compound gadolinium; implies breakdown in the
blood-brain barrier
gamma motor neurons
neurons
that contract the ends of the
muscle spindle
so that spindle sensitivity to passive stretch is kept constant throughout muscle shortening
ganglia
aggregations of nerve cell bodies
gegenhalten
see
paratonia
gemistocyte
reactive
astrocyte
having increased
glial
filaments and glassy eosinophilic cytoplasm
generalized seizure
seizure
that affects both
cerebral hemispheres
simultaneously and causes unconsciousness at the outset
geniculate ganglion
sensory
ganglion
of the
facial nerve
that innervates taste buds on the anterior 2/3 of the tongue
genu
kneelike bend in the anterior part of the
corpus callosum
or
internal capsule
germinal matrix
a highly vascular, metabolically active area of the brain located just beneath the
ependymal
lining of the ventricular walls, which is the source of
neurons
and
glial
cells that will later migrate to
cerebral cortex
. It involutes in the second trimester. Germinal matrix vessels are fragile and are believed to have impaired
autoregulation
, making them prone to rupture in premature infants, resulting in intraventricular hemorrhage.
Gerstmann syndrome
a neurological disorder that includes a writing disability (
agraphia
or
dysgraphia
), a lack of understanding of the rules for calculation or arithmetic (
acalculia
or dyscalculia), an inability to distinguish right from left and an inability to identify fingers (
finger agnosia
) that is due to a lesion of the
angular gyrus
of the dominant parietal lobe
Glasgow coma acale (GCS)
most widely used scoring system to quantify level of consciousness following traumatic brain injury; scores range from 3 to 15, based on the sum of the best eye opening response, the best verbal response and the best motor response
Eye Opening (E)
Verbal Response (V)
Motor Response (M)
4=Spontaneous
5=Normal
6=Normal
3=To voice
4=Disoriented
5=Localizes to pain
2=To pain
3=Inappropriate
4=Withdraws to pain
1=None
2=Incomprehensible
3=Flexes to pain
1=None
2=Extends to pain
1=None
Total
= E+V+M
glia
supporting cells of the nervous system that provide structural and metabolic support for the
neurons
; includes
astrocytes
oligodendrocytes
ependymal cells
and
microglia
glioblastoma multiforme
WHO grade
IV astrocytoma characterized by hemorrhagic necrosis, endothelial proliferation, ± crossing of the
corpus callosum
ring-enhancement
on imaging and poor survival
gliosis
scar or dense fibrous network of
glial
processes in an area of
CNS
injury
global aphasia
impairment of language production, comprehension, and repetition due to lesion of entire perisylvian region; usually associated with right
hemiparesis
globus pallidus
most medial component of the
basal ganglia
and generator of most basal ganglionic output
glossopharyngeal nerve (cranial nerve IX)
nerve containing motor, sensory, and
parasympathetic
fibers; motor fibers originate in the
nucleus ambiguus
and innervate the stylopharyngeus to elevate the palate; sensory fibers originate in the superior and petrosal ganglion and supply taste to the posterior third of the tongue and tactile sensation to the posterior tongue, pharynx, middle and external ear and eustacian tube; parasympathetic fibers originate in the inferior salivatory nucleus and carry secretory and vasodilatory fibers to the parotid gland
Golgi tendon organs
sense active stretch and via inhibitory
inter-neurons
inhibit the motor
neurons
to provide protection against hurtful contractile forces Gower’s sign maneuver used by patients with proximal muscle weakness (as in
myopathy
) in order to arise from the floor or from a kneeling or squatting position; the hands are used to “walk up” the thighs
Gradenigo syndrome
ipsilateral
lateral rectus palsy, peripheral facial palsy, decreased hearing, and upper facial pain due to a lesion in the apex of the temporal bone
grand mal seizure
see
tonic-clonic seizure
graphesthesia
ability to recognize letters or numbers drawn on the finger or palm
gray matter
part of the
CNS
consisting of
neuronal
cell bodies and
dendrites
Guillain-Barre syndrome (acute inflammatory
demyelinating
polyneuropathy)
acute, ascending, and progressive
neuropathy
believed to result from an autoimmune response triggered by an antecedent illness or various medical conditions and characterized by weakness,
paresthesias
, hyporeflexia and labile
autonomic
dysfunction; most patients exhibit absent or profoundly delayed conduction in nerve fibers resulting from
demyelination,
but in a subset of patients, there is a direct cellular immune attack on the
axon
itself
gustatory
relating to the sense of taste
gyrus
convoluted ridge on the outer surface of the brain caused by infolding of the
cerebral cortex
and bound by
sulci
habenula
diencephalic
structure located on the dorsomedial surface of the
caudal
thalamus
that receives
afferents
from the septal
nuclei
and
hypothalamus
via the
stria medullaris
and projects to
midbrain
nuclei
; involved in
autonomic
processing
hangman’s fracture
fracture through bilateral pedicles of C2 via various mechanisms; typically unstable
hemianesthesia
loss of somatosensation on one half of the body
hemianopia
loss of vision in one half of the visual field, indicating a pathological process posterior to the
optic chiasm
hemiballismus
involuntary violent flinging or jerking of a limb (or limbs) in an uncoordinated manner caused by a lesion of the
contralateral
subthalamus
hemicrania continua
indomethacin-responsive headache
disorder characterized by steady, moderately intense unilateral head pain on which are superimposed episodes of more intense pain with
autonomic
symptoms (eye tearing, eye redness, eyelid edema, nasal congestion, runny nose) occurring several times a day
hemifacial spasm
segmental
myoclonus
of muscles innervated by the facial nerve; may be due to vascular compression of the facial nerve or facial nerve injury or tumor, or it may have no apparent cause
hemifield
one-half of the binocular visual field
hemiparesis
weakness on one side of the body
hemiplegia
paralysis
on one side of the body
hemiplegic migraine
familial form of migraine characterized by temporary (usually < 1 hour but occasionally lasting up to a week)
hemiparesis ±
hemisensory symptoms often associated with visual
aura
and headache; in about 50% of affected families, a defect may be found on chromosome 19 or on chromosome 1 and involves abnormal calcium channels
heterotopia
tissue occurring in an abnormal anatomical position
hindbrain
medulla
pons
and
cerebellum
hippocampal formation
cortical
structure in the medial temporal lobe comprising the dentate
gyrus
hippocampus
and
subiculum
; involved in short-term declarative memory
hippocampus
convoluted structure at the medial margin of the
cortical
mantle of the
cerebral hemisphere
, bordering the choroid fissure of the lateral ventricle and forming part of the
limbic
system, which is concerned with memory and emotion
Hoffman’s sign
contraction of fingers and thumb when a stimulus is applied to a distal phalanx in that hand; indication of hyperreflexia in the upper extremity
holoprosencephaly
failure of cleavage at the
rostral
end of the notochord resulting in midline fusion of the frontal lobes, midline facial abnormalities and often
hydrocephalus
and
heterotopias
Homer-Wright rosette
halo of cells surrounding a central lumen containing
neuropil
; found in
medulloblastomas
and
PNETs
homotopic
geometrically corresponding regions e.g., in each cerebral hemisphere
Horner’s syndrome
ptosis
miosis
and
anhidrosis
ipsilateral
to damaged sympathetic nerve fibers
h-reflex
electrical equivalent of the monosynaptic stretch reflex elicited by selectively stimulating the Ia fibers of the posterior tibial or median nerve
Hunt and Hess scale
scale for grading clinical status in patients with nontraumatic
subarachnoid hemorrhage
that correlates well with clinical outcome
Description
Grade
Asymptomatic, mild headache, slight nuchal rigidity
Moderate to severe headache, nuchal rigidity , no neurologic deficit other than cranial nerve palsy
Drowsiness / confusion, mild focal neurologic deficit
Stupor, moderate-severe hemiparesis
coma
, decerebrate posturing
Huntington disease
fatal autosomal dominant neurodegenerative disorder characterized by
chorea
and progressive
dementia
; due to a trinucleotide CAG-repeat mutation on chromosome 4
hydranencephaly
birth defect in which the majority of the
cerebral hemispheres
and
striatum
are absent and replaced by sacs filled with
cerebrospinal fluid
; considered to be an extreme form of
porencephaly
hydrocephalus
literally “water on the brain;” increase in size of ventricles and amount of
cerebrospinal fluid
in the brain
hyperacusis
abnormally increased sensitivity to sound
hyperpathia
exaggerated response to painful stimuli
hypersomnolence
see
excessive daytime sleepiness
hypertensive hemorrhage
intraparenchymal hemorrhage with a predilection to occur deep in the
cerebral hemispheres
, especially in the
putamen
thalamus
and deep
white matter
, as well as the
pons
and
cerebellum
. These sites are all supplied by small penetrating arteries that are subject to high sheer stress and have no collaterals, making them vulnerable to the effects of increased blood pressure
hypertonicity
increase in passive muscle resistance, such as
spasticity
or
rigidity
hypertropia
an eye with
strabismus
that deviates up
hypnagogic hallucination
vivid dreamlike hallucination that occurs as one is falling asleep; one of the symptoms of
narcolepsy
, but also experienced by some non-narcoleptic individuals
hypnic headache
indomethacin-responsive headache
disorder characterized by diffuse, throbbing headache arising exclusively during sleep, typically between 1:00 – 3:00 a.m.
hypnic
jerk sensation of falling, and then “jerking” awake just as one drifts to sleep
hypnopompic hallucination
vivid dreamlike hallucination that occurs as one is waking up; one of the symptoms of
narcolepsy
, but also experienced by some non-narcoleptic individuals
hypoglossal nerve (cranial nerve XII)
motor nerve that innervates all tongue muscles except the palatoglossus; lesions result in deviation of the protruded tongue towards the paralyzed side and deviation of the tongue at rest away from the paralyzed side;
nucleus
is located in the
medulla
hypomimia
see
facial masking
hypophysis
see
pituitary gland
hypothalamus
basal part of the
diencephalon
that controls hunger, thirst, body temperature and various metabolic processes, including the maintaining of water balance
hypotonicity
reduction in passive muscle resistance
hypotropia
an eye with
strabismus
that deviates down
hypoxia
reduction in the supply of oxygen to the brain or other vital organ
hypsarhythmia
abnormal
EEG
pattern of excessive slow activity and multiple areas of
epileptiform
activity; associated with
infantile spasms
ice cream headache
nickname given to headaches that are cold induced; common in migraine
ice-pick headache
indomethacin-responsive headache
disorder characterized by momentary, sharp and/or jabbing pain that occurs either once or several times a day at irregular intervals
ictus
sudden attack,
stroke
, or
seizure
ideational
apraxia
impairment of the conceptual system for action leading to poor gesture comprehension/discrimination and production; patients have difficulty both pantomiming and imitating actions (e.g., show me how you would comb your hair/brush your teeth/salute/blow a kiss) and may make tool selection errors; often due to dominant premotor or parietal lesions
ideomotor
apraxia
impairment of action production system leading to inability to make proper movements or carry out a series of acts in the proper sequence; patients have difficulty both pantomiming and imitating actions (e.g., show me how you would comb your hair/brush your teeth/salute/blow a kiss) but gesture comprehension and discrimination are preserved; often due to dominant premotor or parietal lesions
idiopathic
occurring without known cause; in the context of
epilepsy
, indicates cases in which no lesion is found and a genetic cause is presumed
impairment
problem in body function or structure such as a significant deviation or loss (e.g., weakness = impairment in the muscles’ capability to produce force)
incisura
fissure that separates the
uncus
from the apex of the temporal lobe
incyclotorsion
(a.k.a. intorsion):
cyclotorsion
of an eye such that the superior pole rotates inward
indomethacin-responsive headache
class of primary headache disorders characterized by a prompt and often complete response to indomethacin to the exclusion of other nonsteroidal anti-inflammatory drugs and medications usually effective in treating other primary headache disorders; includes
ice-pick headache
chronic paroxysmal hemicrania
hemicrania continua
cough headache
and
hypnic headache
, among others
infantile spasms
form of
cryptogenic
generalized
epilepsy
characterized by sudden, forceful forward flexion of the trunk and extension of the arms
infarction
permanent tissue damage and death of all cellular elements (
neurons
, glia, vessels) due to prolonged or severe
ischemia
inferior cerebellar peduncle (restiform body)
paired bundle of fibers traveling to and from the
cerebellum
afferent
fibers from the dorsal
spinocerebellar tract
carry
proprioceptive
information from the upper body;
efferent
fibers travel to the vestibular nuclei in the
dorsal
brainstem
inferior colliculus
paired structures on the dorsal surface of the
caudal
midbrain
overlying the
cerebral aqueduct
that process and relay auditory signals from
brainstem
centers to the
medial geniculate nucleus
of the
thalamus
; with the
superior collicui
, make up the
tectum
and the
quadrigeminal bodies
inferior olivary nucleus
prominent
nucleus
in the ventral
medulla
located just lateral and dorsal to the medullary
pyramids
; source of climbing fibers that provide a critical input to the
cerebellum
involved in Purkinje cell plasticity and motor learning
infratentorial
below the
tentorium cerebelli
, i.e.,
brainstem
and
cerebellum
infundibulum
connection between the
hypothalamus
and the
pituitary gland
(also called the “pituitary stalk”); contains the hypophyseal portal veins and the
axons
of
hypothalamic
neurons
that project to the posterior
pituitary
insomnia
difficulty with falling asleep or staying asleep
insula
cerebral cortex
lying in the depths of the
Sylvian fissure
and involved in gustatory, visceral sensory, and emotional processing
intention tremor
tremor
whose amplitude increases as the affected body part (typically a finger) nears an intended target and that may the targeted object to be missed; typically results from damage to the
cerebellum
or its connections
internal capsule
broad compact band of
efferent
and
afferent
fibers that travel to or from the
cerebral cortex
; flanked medially by the
thalamus
and
caudate
and laterally by the
lentiform nucleus
internal carotid artery
artery that arises from the
common carotid artery
at the upper border of the thyroid cartilage and terminates in the
middle cranial fossa
by dividing into the
anterior cerebral artery
and the
middle cerebral artery
; constitutes the anterior circulation of the brain
inter-neuron
neurons
that receives input from one
neurons
and projects to another
neurons
within spinal cord, allowing a greater degree of complexity of movement control
internuclear ophthalmoplegia
failure of adduction of one eye and abducting
nystagmus
of the other eye due to a lesion of the
medial longitudinal fasciculus
intervertebral foramen
bony opening between adjacent vertebrae where spinal nerve roots exit the spinal cord see
vertebrae
intracranial pressure
pressure exerted by the brain, cerebrospinal fluid, and the cerebral blood supply on the intracranial space; measured in centimeters of water (cmH2O) or millimeters of mercury (mmHg); normally < 20 mm/Hg
intrathecal space (
subarachnoid space
) space surrounding the brain and spinal cord that contains
cerebrospinal fluid
intraventricular hemorrhage (IVH)
bleeding in the
ventricles
especially from fragile blood vessels in premature infants; in adults may accompany intracerebral or
subarachnoid hemorrhage
ipsilateral
located on the same side of the body (brain)
ischemia
impairment of tissue function due to a reduction in blood supply relative to metabolic demand
ischemic penumbra
see
penumbra
Jacksonian march
contiguous spread of electrical discharges through superficial
cortex
occurring with some
seizures
manifested by spread of muscular jerks to contiguous anatomical areas, such as when the jerking begins in the thumb and then spreads stepwise to the fingers, wrist, forearm, proximal arm, shoulder and face
JC virus
member of the papovavirus family that produces
progressive multifocal leukoencephalopathy
; “JC” stands for the initials of the first patient described with the virus
Jefferson fracture
burst fracture of the anterior and posterior arches of C1 due to axial loading; typically stable
jitter
measure of the variability of potentials of two muscle fibers innervated by an individual
axon
as measured by
single fiber electromyography
; increased in
myasthenia gravis
juvenile myoclonic epilepsy (JME)
primary generalized
epilepsy
syndrome usually beginning between ages 5 to 17 years, characterized by
myoclonic
(muscle-jerk),
absence
and
tonic-clonic seizures
Kernig’s sign
pain in the posterior aspect of the thigh in response to passive flexion of the thigh and extension of the knee; indicative of
meningeal
irritation
Kernohan’s notch
compression of the opposite
cerebral peduncle
against the edge of the tentorium
contralateral
to a herniating
uncus
; results in
ipsilateral
hemiparesis
ketogenic diet
high-fat, low-carbohydrate diet sometimes used to control
seizures
kindling
process by which repeatedly applying subconvulsive stimulation either electrically or chemically permanently lowers the threshold for having
seizures
; used as an experimental model for
epilepsy
Korsakoff syndrome
chronic phase of thiamine deficiency characterized by impairment in establishing new memories and retrieving previous memories, occurring most commonly in alcoholics
Krabbe disease
(globoid cell leukodystrophy) autosomal recessive disease arising in infancy with progressive motor and mental retardation and peripheral nerve dysfunction due to a deficiency in the enzyme galactocerebrosidase, which is necessary to degrade galactocerebroside, a
myelin
constituent
kuru
fatal
prion
disease restricted to the Fore tribe in the highlands of New Guinea as a result of cannibalistic funeral practices; form of
spongiform encephalopathy
L’hermitte’s sign
transient electrical shock-like sensation extending down the spine and sometimes into the limbs that is triggered by neck flexion; a sign of demyelination or other damage to the dorsal columns of the cervical spinal cord.
lacune (lacunar stroke)
small (<2 cm)
infarct
, caused by occlusion of a single penetrating branch of a larger cerebral artery
Lambert-Eaton myasthenic syndrome
autoimmune disorder of neuromuscular transmission characterized by antibodies directed against the voltage-gated calcium channels on the presynaptic motor nerve terminal leading to impaired release of acetylcholine and causing proximal muscle weakness, hyporeflexia and autonomic changes (e.g., dry mouth); associated with malignancy (particularly small cell lung cancer) in half to ¾ of affected individuals
laminar necrosis
selective neuronal loss in layers 3 and 5 of the
cerebral cortex
due to hypoxic-ischemic insult
lateral medullary syndrome (Wallenberg’s syndrome)
constellation of symptoms including difficulty swallowing, hoarseness,
vertigo
nystagmus
ataxia
, loss of pain and temperature sense in the
ipsilateral
face and
contralateral
body and ipsilateral
Horner’s syndrome
in association with an
infarct
in the lateral
medulla
; due to occlusion of the
vertebral
or posterior inferior
cerebellar
artery
Lennox-Gastaut syndrome
syndrome of mental retardation, generalized
epilepsy
(with mixed
seizures
, especially
tonic
, myoclonic and atypical absence) and a characteristic pattern of slow, generalized
spike-and-wave
activity on the
electroencephalogram
lentiform nucleus (lenticular nucleus)
lens-shaped part of the
basal ganglia
consisting of the
putamen
and
globus pallidus
leptomeninges
arachnoid mater and
pia
mater
leukodystrophy
metabolic
demyelinative
disease
Lewy body
cytoplasmic, bright red sphere often with a surrounding halo on H&E composed of an amorphous granular core with a radiating filamentous periphery; believed to contain alpha-synucein; seen in
Parkinson disease
and
diffuse Lewy body disease
Lewy body dementia
see
diffuse Lewy body disease
light-near dissociation
absent pupillary light response but intact near response (i.e., “accommodate but don’t react”) seen with dorsal
midbrain
lesions, syphilis and diabetes
limbic
referring to the system comprising the
hippocampus
, parahippocampal
gyrus
cingulate gyrus
fornix
and multiple
subcortical
structures including portions of
hypothalamus
and
thalamus
; important in memory and emotion
lipohyalinosis
eosinophilic deposits in the connective tissue of the walls of perforating arterioles in the deep portions of the brain due to hypertension; contributes to the development of
lacunar infarction
and
hypertensive hemorrhage
Lissauer’s tract
longitudinal bundle of thin, unmyelinated and poorly myelinated fibers capping the apex of the posterior horn of the spinal
gray matter
, composed of posterior nerve root fibers and short association fibers that interconnect neighboring segments of the posterior horn
lissencephaly (agyria)
smooth brain (absence of secondary sulci)
lobe
one of four major portions of the
cerebral cortex
named after the overlying cranial bones: frontal, parietal, temporal, and occipital
locked-in state
tetraplegia
and
aphonia
with preserved consciousness due to
brainstem
(usually pontine) lesion that spares the
reticular activating system
locus ceruleus
melatonin-containing
nucleus
located on the dorsal wall of the upper
pons
that is one of the main sources of neuroepinepherine in the brain and has widespread projections to other parts of the nervous system; mediates arousal and primes
neurons
throughout the nervous system to be activated by stimuli
Loftstrand crutch
type of crutch with an attached holder for the forearm that provides extra support
long-tract signs
signs referable to the
corticospinal tract
spinothalamic tract
and
dorsal columns
medial lemniscus
lower motor neuron
2nd order
neurons
whose cell bodies are located in the
brainstem
or anterior horn of the spinal cord and that leave the
CNS
to connect to muscle; lesions result in
flaccid
weakness, reflex loss, atrophy, +/-
fasciculations
lumbar puncture
procedure in which a needle is inserted through the skin between the fourth and fifth lumbar vertebrae and into the lumbar
subarachnoid space
for measurement of
cerebrospinal fluid
analysis
macrocephaly
head circumference that is more than 2 standard deviations above the mean for age, sex, race and gestation
macula
part of the retina responsible for detailed central vision magnetoencephalography (MEG) noninvasive functional neuroimaging technique used to measure magnetic fields generated by intracellular electrical currents from brain
neurons
; clinical uses include localization of epileptic discharges and localization of
eloquent cortex
or surgical planning
mammillary bodies
pair of
nuclei
in the posterior, ventral and medial
hypothalamus
that receive hippocampal inputs via the
fornix
and project to anterior
nucleus
of the
thalamus
and the
tegmentum
of the
midbrain
and
pons
; involved in memory processing
Marcus-Gunn pupil
see
afferent pupillary defect
mass effect
structural damage due to a lesion’s bulk (e.g., tumor,
infarct
, or hemorrhage), the blockage of fluid movement (e.g., compression of a ventricle), or excessive accumulation of fluid
medial geniculate nucleus
nucleus
of the posterior, dorsal
thalamus
that receives auditory input from the
inferior colliculus
and relays this information to the primary auditory
cortex
(Brodmann’s areas 41 & 42) in the superior temporal gyrus.
medial lemniscus
ascending
axonal
tract in the
brainstem
that carries tactile and
proprioceptive
information from the
dorsal column
nuclei
to the ventral posterior lateral
nucleus
of the
thalamus
medial longitudinal fasciculus
pathway connecting the
ipsilateral
3rd nerve
nucleus
in the
midbrain
to the
contralateral
6th nerve
nucleus
in the
pons
for ocular motor control
medication overuse headache (analgesic rebound headache)
headache disorder characterized by headache that is present on 15 or more days per month in association with the use of any analgesic (including aspirin, acetaminophen, narcotics, ergotamine and triptans) at least two or three days each week, with intake of the drug on at least 10 days per month for at least three months; headache resolves or reverts to its previous patterns within two months after discontinuation of the drug
medulla
a part of the brainstem that helps regulate respiration and other behaviors
medulloblastoma
aggressive
WHO
grade IV primitive neuroepithelial tumor of children and young adults typically involving the
posterior fossa
sometimes with
cerebrospinal fluid
seeding (
drop metastases
); characterized histologically by small blue cells and Homer Wright rosettes
medulla oblongata (myelencephalon)
caudal
aspect of the
brainstem
located between the
pons
and the spinal cord
megalencephaly
abnormally large, heavy and usually malfunctioning brain; thought to be related to a disturbance in the regulation of cell reproduction or proliferation
Meissner corpuscles
dermal mechanoreceptors that subserve light touch sensation
MELAS (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes)
mitochondrial disorder characterized by hearing loss, episodic vomiting and recurrent cerebral insults resembling
strokes
and causing
hemiparesis
hemianopia
or
cortical blindness
meningeal carcinomatosis
diffuse infiltration of the
meninges
by metastatic tumor cells often with positive
cerebrospinal fluid
cytology
meninges
three distinct connective tissue membranes (from outer to inner:
dura
arachnoid
and
pia
mater) that enclose and protect the
central nervous system
meningioma
slow-growing
WHO
grade I meningeal neoplasm that has an extra-axial location and often shows a
dural tail sign
and hyperostosis of adjacent skull; characterized histologically by whorls and psammoma bodies
meningitis
inflammation of
meninges
and spinal fluid
meningocele
form of
spina bifida
in which there is herniation of only
meninges
(no spinal cord
parenchyma
) through defective posterior arches meninx singular form of
meninges
menstrual (catamenial) migraine
migraine occurring between one day before and four days after the onset of menses; thought to be due to estrogen withdrawal
Merkel cells
disk-shaped receptor endings in the skin believed to be involved with the sensation of fine touch
mesencephalon
see
midbrain
mesial temporal sclerosis
hippocampal
scarring and volume loss; most common cause of
temporal lobe epilepsy
Mesulam syndrome
eponym for
primary progressive aphasia
metachromatic leukodystrophy
autosomal recessive disease associated with large confluent areas of discolored gelatinous
white matter
caused by deficiency of the enzyme arylsulfatase A, which is necessary for the degradation of sulfatide, a
myelin
constituent
Meyer’s loop
part of the
optic radiations
that fans out into the temporal lobe and carries information from the upper visual world
microcephaly
head circumference that is smaller than normal because the brain has not developed properly or has stopped growing; most often caused by genetic abnormalities
microglia
bone marrow derived phagocytic cells that are involved in immune reactions in the
CNS
microglial nodules
formation of clusters of activated
microglia
around foci of necrotic brain tissue
micrographia
small, cramped handwriting
midbrain (mesencephalon)
rostral
aspect of the
brainstem
located between the
pons
and the
diencephalon
middle cerebellar peduncle (brachium pontis)
paired bundle of fibers originating from the
pontine
nuclei,
decussating
in the base of the
pons
and ending in the
contralateral
cerebellar cortex
middle cerebral artery
branch of the
internal carotid artery
; supplies blood to the entire lateral aspect of each hemisphere including the lateral motor strip, lateral sensory strip, language areas,
putamen
globus pallidus
and
internal capsule
middle cranial fossa
butterfly-shaped portion of the internal base of the skull housing the temporal lobes laterally and the
pituitary
centrally
migraine headache
attacks lasting 4-72 hours consisting of moderate to severe intensity unilateral, pulsating head pain that is aggravated by routine physical activity, inhibits daily activities, and is associated with nausea/vomiting,
photophobia
and
phonophobia
migraine aura
focal neurological phenomena (visual, sensory, motor, or language) preceding or accompanying a migraine attack, usually developing over 5-20 minutes and lasting < 1 hour; may occur in isolation or before (most commonly), during or after the onset of headache
migraine with aura (classic migraine)
migraine attack associated with reversible
aura
symptoms indicative of focal
CNS
dysfunction; the
aura
scintillating scotoma
vertigo
paresthesias
paresis
, etc) typically develops gradually over several minutes, lasts less than 60 minutes, and occurs before, during or after headache
migraine without aura (common migraine)
migraine attack without associated neurological deficits
mild cognitive impairment (MCI)
cognitive changes intermediate between normal aging and clinically diagnosed
Alzheimer disease
; identifies individuals believed to be at risk for
Alzheimer disease
Millard-Gubler syndrome
ipsilateral
lateral rectus palsy, ipsilateral peripheral facial palsy, and
contralateral
hemiplegia
due to a
ventral
pontine
lesion affecting the
abducens
and
facial nerve
fascicles
and
corticospinal tract
miosis
pupillary constriction
mitochondrial myopathies
neuromuscular diseases caused by damage to the mitochondria (small, energy-producing structures found in every cell in the body )
Mollaret meningitis
benign recurrent
aseptic meningitis
mononeuropathy multiplex (mononeuritis multiplex) condition associated with various systemic disorders (e.g., diabetes, polyarteritis nodosa) characterized by isolated damage to two or more nerves; a multifocal peripheral
neuropathy
Monroe-Kellie doctrine
doctrine stating that the total cranial volume tends to remain constant. An increase in the volume of any of its three components (brain, blood or
CSF
) or the addition of a space-occupying lesion (e.g., tumor) occurs at the expense of the volume of the other components; once the components have redistributed as much as they can, any further increase in volume results in increased
intracranial pressure
Moro reflex
normal neonatal reflex consisting of symmetric abduction followed by adduction of both arms, elicited by gently allowing the back of the head to drop; present during the first 4-6 months of life
motor neglect
inability to look or reach toward left-sided objects
motor neuron
nerve cell that directs movement
motor neuron disease
dysfunction of
alpha motor neurons
; motor
neuronopathy
motor unit
motor neuron
axon
and the individual muscle fibers it branches to contact
moyamoya syndrome
usually bilateral, progressive occlusive disease of the large cerebral arteries leading to the development of an abnormal collateral vascular network adjacent to the stenotic vessels; manifest most commonly by
infarcts
in children and hemorrhages in adults
Muller’s muscle
eyelid muscle innervated by the
sympathetic nervous system
and that functions to elevate the upper eyelid; interruption of these sympathetic fibers results in the
ptosis
that is part of
Horner’s syndrome
multi-infarct dementia
form of
vascular dementia
involving deterioration of mental function caused by
infarcts
in multiple brain regions
multiple sclerosis
inflammatory
demeyelating
disease with relative
axonal
sparing of the
central nervous system
usually characterized by recurrent attacks of focal and multifocal neurological disability
multiple sleep latency test (MSLT)
standard test used to quantify the overall daytime sleep tendency by measuring the speed of falling asleep (sleep latency) usually in 5 tests carried out at two-hour intervals
multisystems atrophy (MSA)
collective term for a group of
Parkinson plus syndromes
involving various degrees of
parkinsonism
autonomic
failure,
cerebellar
dysfunction and
pyramidal
signs that are poorly responsive to levodopa or dopamine agonists; pathologic hallmarks are
glial
cytoplasmic inclusions and a
neuronal
multisystem degeneration; replaces the older designations Shy-Drager syndrome,
striatonigral degeneration
and
olivopontocerebellar atrophy
muscle spindle
stretch receptor in vertebrate muscle that is innervated by both sensory and motor
neurons
axons
and sends
proprioceptive
information about the muscle to the
central nervous system
muscle stretch reflex
two-
neurons
reflex in which a sensory
neurons
senses muscle extension and provides direct excitatory feedback to a motor
neurons
innervating the same muscle, causing the muscle to contract
mutism
inability to produce any verbal utterance; may be due to disordered language, speech, or voice or an unwillingness to speak (as in selective mutism)
myasthenia gravis
disease of the
neuromuscular junction
in which an antibody-mediated attack on nicotinic acetylcholine receptors impairs neuromuscular transmission, resulting in fluctuating, fatigable weakness that responds to cholinergic drugs
mycotic aneurysm
infective
aneurysm
typically developing distal to the
Circle of Willis
and reflecting local bacterial or fungal intramural growth with rupture of the vascular wall
mydriasis
pupillary dilation
myelencephalon
see
medulla
myelin
fatty substance forming an insulating sheath around
axons
to increase the velocity of action potential conduction; produced by
oligodendrocytes
in the
CNS
and by
Schwann cells
in the
PNS
myelitis
inflammatory disease of the spinal cord
myelogram
diagnostic procedure in which contrast material is injected into the spinal
subarachnoid space
allowing visualization of the spinal cord and nerve roots
myelomeningocele
form of
spina bifida
in which there is herniation of
meninges
and spinal cord
parenchyma
through defective posterior arches
myelopathy
symptoms and signs associated with spinal cord compression
myoclonus
sudden, shock-like, jerking contraction of a group of muscles
myokymia
involuntary repetitive contractions of muscle fibers lasting a few seconds and giving a continuous rippling or undulating appearance to the overlying skin; associated with nerve irritation
myopathy
muscle disease; manifested by
lower motor neurons
weakness that is usually proximal>distal
myotonia
muscle disorder characterized by abnormally prolonged contraction (delayed relaxation of the muscle after a forceful contraction)
narcolepsy
sleep disorder characterized by excessive daytime sleepiness and dysregulated REM sleep
near reflex triad
convergence, accommodation, and pupilloconstriction evoked by targets that move close to you
negative symptom
reduction (weakness, numbness) or complete loss (
paralysis
, analgesia) of function; implies at least partial or complete failure of impulse conduction in a functional system
neglect
failure to acknowledge stimuli toward the side of space opposite to a hemispheric (usually parietal) lesion
Negri body
viral inclusion in hippocampal, neocortical, or Purkinje cell neurons that is the diagnostic hallmark of rabies
encephalitis
neologism
made-up word
nerve conduction velocity study
method of diagnosing the type and location of nerve injury using application of electrical stimulation to the nerve
network inhibition hypothesis
proposed pathophysiological mechanism for complex behavioral phenomena and impaired consciousness in
complex partial seizures
; theory is that the
seizures
induce excitation in the temporal lobe that propagates to the dorsomedial
thalamus
and upper brainstem
reticular formation
, disrupting the normal activating functions of these areas and resulting in widespread functional depression of bilateral frontal and parietal
association cortex
neuralgia
pain that follows the paths of specific nerves, e.g., trigeminal neuralgia; postherpetic neuralgia
neural plate
ectodermal tissue on the
dorsal
surface of the embryo that forms the
neural tube
, which develops into the
central nervous system
neural tube
embryonic brain and spinal cord neural tube defect malformation of the brain and/or spinal cord in embryo; classified based on location, extent and the presence or absence of exposed neural tissue (open or closed)
neuraxis
often used synonymously with
central nervous system
(even though some suggest that it represents only the unpaired portions of the
CNS
neurilemma
thin membrane surrounding the axons and myelin of peripheral nerves; outermost layer of nerve fibers
neurite
terminal
axon
or
dendrite
neuritic plaque
mature plaque composed of a) silver-positive swollen
neurites
engorged with aggregates of paired helical filaments and round dense bodies and b) an amyloid core; seen in
Alzheimer’s disease
neurofibrillary tangles
flame-shaped intracytoplasmic inclusions in
cortical
neurons
consisting of paired helical filaments; characteristic of, but not unique to,
Alzheimer’s disease
neurogenic bladder
bladder dysfunction associated with a lesion in the brain, spinal cord, or peripheral nerves and characterized by underactivity (failure to empty) or overactivity (failure to store); symptoms include urinary urgency, frequency, hesitancy, nocturia and incontinence
neuroglia
see
glia
neuroleptic
drug that blocks dopamine receptors; antipsychotic drug
neuroleptic malignant syndrome
rare, but life-threatening, idiosyncratic reaction to antipsychotic drugs that is characterized by high fever, hypertension, severe
rigidity
, altered mental status and
autonomic
dysfunction; may occur with either severe blockade (high doses of neuroleptics) or sudden depletion (withdrawal of neuroleptics) of dopamine receptors
neurologist
a physician who specializes in the diagnosis and treatment of disease of the nervous system
neurology
medical specialty dealing with the nervous system and the diseases affecting it
neuroma
tumor composed of nerve tissue
neuromelanin
dark brown pigment seen in selected neuronal populations (most characteristically in the substantia nigra and locus ceruleus) that represents the residua of catecholamine metabolism
neuromuscular junction
junction (synapse) between the terminal of a motor
neurons
and a muscle fiber; myoneural junction
neuron
nerve cell body
neuronopathy
dysfunction and reflex loss due to disease of cell bodies (sensory=dorsal root ganglion; motor=
alpha motor neurons
, more commonly called motor neuron disease)
neuropathy
nerve disease; manifested by varying combinations of lower motor neuron weakness that is usually distal>proximal, sensory loss and reflex loss
neuronophagia
engulfing of degenerating neurons by hematogenously derived monocytic cells and activated
microglia
neuropil
unmyelinated neuronal processes (axons and dendrites) in the
gray matter
of the central nervous system
neuroprotection
strategies that ameliorate the biochemical and metabolic derangements induced by cerebral
ischemia
, thus limiting delayed
neuronal
injury
neurotransmitter
chemical substance that transmits electrical impulses between
neurons
neurulation
process by which the
neural tube
is formed; consists of folding of the
neural plate
on the dorsal side of the embryo (resulting in the formation of the brain and spinal cord) followed by canalization (resulting in the development of the
caudal
spinal cord)
nightmare
unpleasant and/or frightening dream that usually awakens a person from REM sleep; affected individual usually remembers the event, unlike in
night terror
night terror (sleep terror; pavor nocturnes)
sleep disorder (usually of children) involving abrupt awakening from sleep in a terrified state that represents incomplete arousal from nonREM sleep; affected individual is usually confused and does not remember details of the event, unlike in nightmare
nociceptive
painful
nodulus
posterior part of the cerebellar
vermis
; medial portion of the vestibulocerebellum
non-communicating hydrocephalus
blockage of
CSF
flow along one or more of the narrow pathways connecting the
ventricles
(most commonly the
cerebral aqueduct
non-fluent aphasia (Broca’s or expressive aphasia)
selective impairment of language production including impaired repetition due to a lesion of the left inferior frontal lobe (
Brodmann areas
44 and 45)
non-REM sleep (non-rapid eye movement sleep, slow wave sleep)
sleep stages 1 through 4; characterized by a slowing of brain waves and some physiological functions
normal pressure hydrocephalus (NPH)
clinical symptom complex characterized by abnormal gait, urinary incontinence, and
dementia
in the setting of hydrocephalus with normal
cerebrospinal fluid
pressure; proposed pathophysiology is that there is diminished
cerebrospinal fluid
absorption at the
arachnoid
villi, which leads to transient high-pressure
hydrocephalus
with subsequent ventricular enlargement and return of
cerebrospinal fluid
pressure to normal
Nothnagel syndrome
ipsilateral
oculomotor
palsy and
contralateral
ataxia
due to a
midbrain
tegmental
lesion affecting the III nerve
fascicle
and
superior cerebellar peduncle
notochord
embryological predecessor of the vertebral column
nuchal
rigidity
stiff neck
nucleus
collection of
neuronal
cell bodies
nucleus ambiguus
motor nucleus in the dorsolateral medulla that innervates striated muscle in the neck and thorax
nucleus cuneatus
nucleus
located in the lower
medulla
containing the second-order sensory
neurons
that relay mechanosensory information from peripheral receptors in the upper body to the
thalamus
via the
medial lemniscus
nucleus gracilis
nucleus
located in the lower
medulla
containing the second-order sensory
neurons
that relay mechanosensory information from peripheral receptors in the lower body to the
thalamus
via the
medial lemniscus
nystagmus
involuntary, rhythmic oscillation or trembling of the eyeballs
obstructive sleep apnea
repetitive cessation of breathing during sleep for 10 seconds or more due to complete closure of the throat; characterized by snoring, excessive daytime sleepiness and morning headache
obtundation
mild to moderate reduction in alertness with slow response to stimulation, decreased interest in environment and increased number of hours of sleep
ocular migraine
form of migraine characterized by monocular visual loss typically followed by an
ipsilateral
periorbital (or less commonly diffuse) headache
oculocephalic response (OCR/Doll’s phenomenon)
reflex eye movements assessed in an uncooperative or unresponsive patient to determine whether
brainstem
extraocular pathways are intact; performed by quickly turning the head, stimulating
proprioceptive
afferents
from the neck and/or the vestibular system; considered positive (brainstem pathways intact) if head turn produces conjugate eye deviation in the opposite direction; absent response implies that either brainstem pathways are impaired or the patient is too awake to assess
oculogyric crisis
acute dystonic reaction to neuroleptic drugs manifested by sudden sustained twisting of the head and upward deviation of the eyes; responsive to anticholinergic or antihistamine medications
oculomotor nerve (cranial nerve III)
motor nerve innervating the superior, inferior, and medial recti, inferior oblique, and levator palpebrae superioris muscles and providing preganglionic
parasympathetic
fibers to the ciliary ganglion to control pupillary constriction; III palsy causes down and out eye deviation,
ptosis
and a dilated unreactive pupil (pupillary fibers on the outside so spared with intrinsic lesion); lesions of the
nucleus
, located in the medial
midbrain
, typically cause weakness of all muscles innervated by the
ipsilateral
III nerve,
contralateral
superior rectus weakness and bilateral incomplete ptosis;
oculovestibular response (OVR/cold calorics/vestibulo-ocular response/VOR)
reflex eye movements that keep vision stable upon head rotation and involve connections between the
ipsilateral
8th and 3rd and the
contralateral
6th nerve
nuclei
; horizontal movements are tested by instilling ice water into one ear, stimulating the lateral semicircular canal; in a normal awake patient, the eyes will slowly deviate towards the irrigated ear and then beat quickly away from the irrigated ear as the supratentorial frontal eye fields try to re-fix vision
odontoid fracture
fracture through the odontoid process of C2 due to horizontal shearing and axial loading; type I usually stable and type II usually unstable
olfactory nerve (cranial nerve I)
sensory nerve mediating smell
oligemia
reduction in blood flow associated with an increase in oxygen extraction fraction but maintenance of normal metabolism
oligoclonal bands
two to five bands of immunoglobulins on protein electrophoresis of
cerebrospinal fluid
seen in
multiple sclerosis
and other
central nervous system
disorders
oligodendrocytes
form of
CNS
glia
responsible for the synthesis and maintenance of
myelin
and the formation of perineuronal satellites
oligodendroglioma
WHO
grade II primary
CNS
tumor typically involving the
cerebral hemispheres
; characterized histologically by uniform round
nuclei
with a perinuclear halo (
fried egg artifact
) and perineuronal satellitosis
olivopontocerebellar atrophy (OPCA)
older term for a variant of
multisystems atrophy
characterized by preferential degeneration of the
cerebellum
and
brainstem
producing symmetric
parkinsonism
and
ataxia
dysarthria
dysphagia
pyramidal
signs and often ocular motility disorders
Ondine’s curse (central alveolar hypoventilation)
condition in which the respiratory center in the brain is unable to stimulate breathing in response to an increased amount of carbon dioxide in the blood; typically worsens during sleep
one-and-a-half syndrome
combination of an
abducens
nerve
nuclear
lesion and an ipsilateral
medial longitudinal fasciculus
lesion resulting in an
ipsilateral
gaze paralysis and loss of
adduction
of the ipsilateral eye
on-off phenomenon
sudden, unpredictable changes in motor performance by patients on levodopa therapy
opening pressure
cerebrospinal fluid
pressure obtained upon entering the
subarachnoid space
by spinal puncture
ophthalmoplegia
paralysis
or weakness of one or more of the muscles that control eye movement
ophthalmoplegic migraine
form of
migraine
characterized by periorbital pain and ocular cranial nerve
palsy
(usually the third nerve and including
ptosis
and a dilated pupil)
opisthotonos
abnormal posturing of the body with severe arching of the back and the head thrown backwards; may occur with
meningea
l irritation, especially in infants or with depressed brain function
optic atrophy
wasting of the optic disc that results from partial or complete degeneration of optic nerve fibers and is associated with a loss of visual acuity
optic chiasm
partial crossing of about half the
axons
in each
optic nerve
to enter the
contralateral
optic tract; lesion results in loss of vision in the temporal hemifield of both eyes
optic disc
(optic nerve head) location where all the ganglion cells exit the retina to form the optic nerve; known as the blind spot since there are no receptors in this part of the retina
optic nerve
extent of the visual system pathway from the retina to the
optic chiasm
; contains
axons
of ganglion cells in the retina of the
ipsilateral
eye; lesion results in loss of vision in one eye
optic neuritis
inflammation or
demyelination
of the optic nerve with transient or permanent loss of vision +/- pain
optic radiations
extent of the visual system pathway from the lateral geniculate
nucleus
of the
thalamus
to primary visual
cortex
in the occipital lobe; involves temporal (Meyer’s loop) and parietal lobes
optic tract
extent of the visual system pathway from the
optic chiasm
to the lateral geniculate
nucleus
of the
thalamus
; contains
axons
from ganglion cells in the retinas of both the left and right eyes, but information from only one half (either left or right) of each eye’s visual field; lesion results in loss of vision in
contralateral
hemifield of both eyes
optokinetic nystagmus
reflexive eye movement that consists of the intermittent rotation of the eye when a subject looks at moving objects; designed to keep an entire moving scene stable on the retina so that it doesn’t blur
orthostatic hypotension
sudden drop in blood pressure experienced upon standing up
orthotic
mechanical appliance such as a leg brace or splint that is designed to control, correct, or compensate for impaired limb function
oscillopsia
visual disturbance characterized by continuous, involuntary and chaotic eye movements, which make objects appear to be jumping or bouncing
osmophobia
enhanced sensitivity to odors
oxycephaly
premature fusion of all cranial sutures producing an elongated head
oxygen extraction fraction
the fraction of available oxygen extracted by the brain from the blood
pachymeninges
dura mater (
pachy
means thick)
Pacinian corpuscle
largest of the skin receptors located deep in the dermis and responsible for sensation of vibration and deep pressure
palsy
paralysis
of a muscle group
papilledema
swelling of nerve head usually but not always due to increased ICP
parachute reflex
protective reflex of normal infants (present by 7-9 months) in which both arms go out in front in response to the head being held down and pointed toward the floor
paralysis
loss of motor function in a body part
paramedian pontine reticular formation (PPRF)
collection of premotor
neurons
located in or near the abducens
nucleus
that drive horizontal gaze when excited by the
cerebral cortex
parameningeal
adjacent to the
meninges
; includes nasal cavity, middle ear, paranasal sinuses, mastoid, infratemporal fossa and pterygopalatine fossa
paraphasia
speech error characterized by substitutions of letters (e.g., “bree” for “tree”) or words (e.g., “house” for “tree”)
paraplegia
paralysis
of both legs
parasagittal
sagittal section that is lateral to the midline
parasomnia
disorder in which abnormal behavior intrudes into the sleep process; includes
somnambulism
night terrors
and bruxism
parasympathetic nervous system
part of the
autonomic nervous system
concerned with conservation and restoration of energy; its preganglionic fibers arise from the motor nuclei of cranial nerves III, VII, IX and X in the
brainstem
and from the second, third and fourth sacral segments of the spinal cord
paratonia (gegenhalten)
increased muscle tone that increases in proportion to the speed and strength with which the examiner tries to move the joint; indicative of extensive bihemispheric or bifrontal dysfunction
parenchyma
tissue
paresis
reduced ability to activate
motor neurons
; weakness
paresthesia
skin sensation, such as burning, prickling, itching or tingling, with no apparent physical cause
Parinaud’s syndrome (dorsal midbrain syndrome)
syndrome characterized by a
supranuclear
palsy
of vertical conjugate movements, convergence-retraction
nystagmus
, and light-near dissociation of the pupillary reflex; eyes may be forced downward; due to lesion of the dorsal
midbrain
including pressure on the it from
hydrocephalus
or increased intracranial pressure
Parkinson disease
neurodegenerative disease characterized by initially asymmetric
resting tremor
bradykinesia
akinesia
rigidity
and postural instability due to loss of cells in the
substantia nigra
with striatal dopamine deficiency and residual Lewy bodies
parkinsonism
complex of symptoms including
resting tremor
bradykinesia
akinesia
rigidity
, and postural instability that are due to striatal dopamine deficiency or reduced function; may be seen in a variety of neurodegenerative disorders including
idiopathic
Parkinson disease
Lewy body dementia
corticobasal degeneration
progressive supranuclear palsy
multisystems atrophy
Parkinson plus syndromes
primary neurodegenerative disorders associated with complex clinical presentations including
parkinsonism
that reflect degeneration in various
neuronal
systems in addition to the
substantia nigra
; parkinsonian features are characterized by symmetry of signs, truncal>appendicular signs, and lack of response to levodopa or dopamine agonists
partial (focal) seizure
seizure
that starts in a single
cortical
region
participation restrictions
problems an individual may experience in their own involvement in life situations (e.g., inability to return to work).
peduncle band
of white matter joining different parts of the brain see
white matter
peduncular hallucinosis
experience of vivid, well-formed usually visual hallucinations that are recognized as being not real; rare manifestation of midbrain pathology
penumbra
area surrounding the dense core of irreversibly damaged cells that has preserved ionic homeostasis and reduced
neuronal
electrical activity but that is capable of recovery
perceptual neglect
inability to distribute spatial attention to objects in the visual field
periaqueductal gray
tegmental
gray matter
surrounding the
cerebral aqueduct
within the
midbrain
that is important in the processing of pain
perimetry visual field
testing designed to determine the sensitivity of specific locations of peripheral and central vision
perineurium
connective tissue sheath surrounding a bundle of nerve fibers
periodic limb movement disorder
sleep disorder characterized by repetitive stereotyped movements during sleep, most commonly an extension of the big toe and dorsiflexion of the ankle; often associated with a partial arousal or awakening of which the patient is typically unaware
peripheral nervous system
cranial and spinal nerves; includes root, plexus, nerve and
neuromuscular junction
perisylvian plexus
referring to structures around the
Sylvian fissure
; includes Wernicke’s area in auditory association cortex and Broca’s area in front of motor cortex
perimysium
connective tissue sheath surrounding a bundle of muscle fibers
petit mal seizure
see
absence seizure
phonophobia
abnormal intolerance to sound that commonly occurs in
migraine
and other headaches
photophobia
abnormal intolerance to light, usually associated with eye pain; characteristic of
meningea
l irritation,
migraine
, optic nerve disease and ocular or retinal disorders
physiologic tremor
subtle low amplitude, high frequency
tremor
most easily observed in the hands that is present in healthy persons and most prominent during posture and action
pia
innermost layer of the
meninges
that is intimately applied to the surface of the brain
parenchyma
and spinal cord and separated from the
arachnoid
by the
subarachnoid space
Pick’s disease
form of frontotemporal
dementia
characterized by a slowly progressive deterioration of social skills and changes in personality in addition to
impairment
of intellect, memory, and language; defined pathologically by Pick bodies (rounded tau-posiotive inclusions similar to neurofibrillary tangles) and Pick cells (swollen or ballooned
neurons
) in a predominantly frontal location
pincer grasp
finger-thumb opposition
pineal
midline body attached to the posterior part of the third
ventricle
and lying between the
superior colliculi
, below the splenium of the
corpus callosum
; major site of melatonin biosynthesis
pituitary apoplexy
spontaneous hemorrhagic
infarction
of a typically large and nonfunctioning
pituitary
adenoma presenting with headache, nausea and vomiting, cranial nerve II, III, IV or VI palsies, altered mental status and hypopituitarism
pituitary gland (hypophysis)
endocrine organ lying ventral to the
hypothalamus
and
optic chiasm
; includes an anterior glandular lobe made up of hormone-secreting cells and a posterior neural lobe containing the terminals of neuropeptide-secreting,
hypothalamic
neurons
placing (stepping) response
normal neonatal reflex consisting of elevating the foot and moving it forward when its dorsal surface is touched; the infant will appear to attempt to stand or walk
plagiocephaly
premature fusion of a unilateral coronal and/or lambdoid +/- sagittal
suture
plantar response
superficial (cutaneous) reflex elicited by applying a stimulus to the skin of the foot or leg; flexion (curling down) of all toes (“downgoing toe”) is a normal response, while extension of the great toe (“upgoing toe”) with fanning of the other toes is abnormal and signifies a lesion of the
corticospinal tract
. Many methods of eliciting the plantar reflex have been described, including the following:
Eponym
Technique
Babinski
Stimulation of the plantar surface of the foot with a blunt point from the heel forward, crossing the metatarsal pad from the small to the great toe
Chaddock
Stimulation of the lateral aspect of the foot with a blunt point from the heel forward to the small toe
Oppenheim
Application of heavy pressure with the thumb and index finger to the anterior surface of the tibia with downward stroking from the infrapatellar region to the ankle
Gordon
Squeezing or applying deep pressure to the calf muscles
Strümpell
Forceful pressure on the anterior tibia
Moniz
Forceful passive plantar flexion of the ankle
Gonda-Allen
Downward snapping of the distal phalanx of the second or fourth toe
Stransky
Gentle extension of the small toe laterally
Bing
Application of pinprick to the dorsal surface of the great toe
plegia
inability to activate any motor
neurons
paralysis
plexus
bundle of intersecting nerves
polymyositis
inflammatory muscle disease associated with primarily proximal limb weakness; considered to be an autoimmune disease of disordered cellular immunity and often associated with a specific collagen-vascular disease
polysomnogram
continuous and simultaneous recording of multiple physiological variables during sleep
pons
middle aspect of the
brainstem
, lying between the
midbrain
rostrally
and the
medulla
caudally
porencephaly
cerebral hemispheric cyst that is usually the remnant of a destructive lesion (e.g.,
stroke
or infection) or is due to abnormal brain development
positive sharp wave
spontaneous muscle activity seen on electromyography in association with denervation or irritable
myopathy
consisting of long action potentials with initial positive (down) wave followed by wide negative (up) wave
positive symptom
exaggeration of a physiological phenomenon; implies abnormal excessive (irritative”) discharges in
gray matter
or (e.g.,
seizure
or hemifacial spasm) or chronic imbalance in complex integrated motor pathways (e.g.,
chorea
postdrome
period following a
migraine
during which a person has impaired concentration, fatigue or irritability
posterior cerebral artery
paired arteries that arise from the top of the
basilar artery
; supply blood to the posterior areas of the brain, including the medial occipital lobes (visual
cortex
), the inferior temporal lobes and
thalamus
posterior commissure
one of the three major groups of commissural fibers that crosses the midline of the epithalamus just dorsal to the point where the
cerebral aqueduct
opens into the third
ventricle
posterior communicating artery
branch of the internal carotid artery that joins the
middle cerebral artery
(anterior circulation) to the posterior cerebral artery (posterior circulation); supplies
thalamus
hypothalamus
optic chiasm
and mammillary bodies
posterior cord syndrome
spinal cord injury syndrome associated with damage to the posterior portion of the spinal cord resulting in bilateral loss of vibration /
proprioception
+/- bilateral weakness below the level of the lesion
posterior fossa
brainstem
and
cerebellum
posterior horn
(dorsal horn)
gray matter
in the back of the spinal cord that receives sensory information from the body through the
dorsal root ganglia
post-herpetic neuralgia
condition following an acute varicella zoster infection (shingles) characterized by persistent pain (3 or more months) in the dermatomal distribution of the previous zoster rash
postural instability
loss of ability to make postural adjustments in response to perturbations, i.e., defect in righting reflex; common in
Parkinson disease
postural tremor
tremor
that occurs with the maintenance of a posture or position against gravity
posture
ability to stand upright automatically against gravity; controlled by the vestibulospinal, reticulospinal and tectospinal pathways
Pott’s disease
tuberculous involvement of the vertebral column with vertebral collapse
praxis
ability to plan, time, sequence and spatially organize skilled movements
prefrontal cortex
cortical
region of the frontal lobe lying anterior to primary and
premotor cortex
; mediates various executive functions, with the dorsolateral division involved in working memory processes, planning and decision making, and the ventromedial division involved in emotion and the organization of appropriate social behavior
premotor cortex
cortical
region (Brodmann’s area 6) in the posterior frontal lobe anterior to the primary motor
cortex
involved in planning or programming of voluntary movements
primary progressive
clinical course of
multiple sclerosis
characterized from the beginning by progressive disease, with no plateaus or remissions or an occasional plateau and very short-lived, minor improvements
primary progressive aphasia
progressive form of
dementia
characterized by global loss of language abilities and initial preservation of other cognitive functions; pathologically, there may be spongiform changes in teh frontal and temporal lobes rather than Alzheimer-like changes
primitive neuroepithelial tumor (PNET)
tumor histologically similar to the
medulloblastoma
but located outside the posterior fossa
prion
proteinacious infectious agent responsible for various fatal brain diseases classified as
spongiform encephalopathy
prodrome
premonitory phenomena occurring hours to days before headache onset in
migraine
consisting of psychological, neurological or constitutional symptoms
progressive multifocal leukoencephalopathy (PML)
fatal
demyelinating CNS
disease of immunocompromised patients caused by reactivation of the JC papovavirus
progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome)
Parkinson plus syndrome
characterized by predominantly axial
rigidity
, akinesia, supranuclear ophthalmoplegia (
impairment
of voluntary vertical gaze—downward more than upward) and pseudobulbar
palsy
proprioception
joint position sense
proptosis (exophthalmos)
abnormal protrusion of the eyeball
prosencephalon
see
forebrain
prosody
emotional content of language pseudoathetosis involuntary slow, writhing movements of a limb (usually the hand or fingers) occurring when the eyes are closed due to impaired
proprioception
. Unlike in
athetosis
, the movements are not present when the eyes are open because visual feedback provides the necessary information to know where the limb is in space.
pseudoathetosis
involuntary, slow, writhing movements usually of the fingers and hands resulting from loss of proprioception
pseudobulbar affect
condition in which episodes of laughing and/or crying occur with no apparent precipitating event
pseudobulbar palsy
syndrome characterized by
dysarthria
dysphagia
, dysphonia,
impairment
of voluntary movements of tongue and facial muscles and emotional lability; caused by diseases such as
multiple sclerosis
, motor
neuron
disease, and
stroke
that affect the motor fibers traveling from the
cerebral cortex
to the lower
brainstem
(i.e.,
corticobulbar tracts
pseudorosette
spoke-wheel arrangement of cells with tapered cellular processes surrounding a blood vessel, creating a perivascular nuclear free zone; seen in most
ependymomas
and less commonly in other CNS tumors
ptosis
eyelid droopiness
pupillary light response
contraction of the pupil on exposure of the retina to light; dependent on proper functioning of the optic and oculomotor nerves
putamen
largest and most lateral component of the
basal ganglia
pyramid
prominent column of
white matter
on the ventromedial margin of the
medulla
containing
axons
of the
corticospinal tract
pyramidal tract
see
corticospinal tract
quad cane
cane that has a broad base on four short “feet,” which provide extra stability
quadrantanopia
loss of vision in either the upper or lower aspect of one hemifield (involving both eyes)
quadrigeminal bodies
two pairs of elevations on the dorsal surface of the
midbrain
; includes the
superior colliculi
and
inferior colliculi
quadriplegia (
tetraplegia
paralysis
of all four extremities
rachischisis
fissure of the spinal cord resulting in exposure of the incompletely folded cord along the back
radiculopathy
symptoms and signs associated with spinal nerve root compression
Ramsy-Hunt syndrome
facial paralysis,
hyperacusis
, loss of taste and vesicles on the eardrum, external auditory meatus, or palate due to herpes zoster infection of the
geniculate ganglion
raphe
ridge of tissue
raphe nuclei
nuclei
located within the medial portion of the reticular formation in the
brainstem
that secrete serotonin
Raymond syndrome
ipsilateral
lateral rectus palsy and
contralateral
hemiplegia
sparing the face due to a
ventral
pontine
lesion affecting the
abducens
nerve
fascicles
and
corticospinal tract
(but sparing the
facial nerve
recurrent-remittent
episodic attacks of symptoms with rapid recovery to normal health; implies repeating episodes of a single process (e.g., transient ischemic attacks (TIA),
seizures
migrain
and
multiple sclerosis
red desaturation
finding of dimmer perception of the color red in an eye affected by
optic nerve
disease such as
optic neuritis
; sign of subtle asymmetry in optic nerve function since color desaturation may occur despite normal visual acuity
red nucleus
oval
nucleus
centrally placed in the upper
midbrain
reticular formation
that receives fibers from the deep
cerebellar
nuclei
and
cerebral cortex
and projects to the
cerebellum
brainstem
, spinal cord and probably
thalamus
reflex epilepsy
form of epilepsy characterized by stimulus-induced seizures. The prototypical reflex epilepsy is photosensitive epilepsy, in which seizures are induced by visual stimuli (e.g., flashing lights) that produce patterns
relapsing-remitting
clinical course of
multiple sclerosis
characterized by episodic attacks of symptoms with recovery to normal health
REM behavior disorder
disorder occurring during REM sleep in which the normal motor
atonia
is partially or completely absent such that dreams can be acted out with punching, kicking and jumping out of bed
REM sleep (rapid eye movement sleep)
sleep stage in which vivid dreaming occurs; identified by the occurrence of rapid eye movements under closed eyelids, motor
atonia
, low voltage
EEG
pattern, bursts of muscular twitching, irregular breathing, irregular heart rate and increased
autonomic
activity.
repetitive nerve stimulation
nerve conduction study
in which a brief series of shocks is applied to a motor nerve before and after brief exercise of a muscle supplied by that nerve; useful for evaluating disorders of neuromuscular transmission such as
myasthenia gravis
(decremental response see) and
Lambert Eaton myasthenic syndrome
(incremental response seen).
restiform body
see
inferior cerebellar peduncle
resting tremor
medium-frequency (3-6 Hz)
tremor
that occurs maximally with the affected body at rest rather than with holding a sustained posture or making an intentional movement; common in
Parkinson disease
restless legs syndrome
sleep disorder characterized by tingling, creepy-crawly or aching sensation in the legs and sometimes arms as well as motor restlessness that tends to occur at rest (especially around the patient’s usual bedtime) and to be relieved temporarily by movement
reticular activating system (RAS)
the activating mechanisms that lie in or near the central
gray matter
of the
diencephalon
midbrain
and
rostral
pons
and are responsible for mediating consciousness
reticular formation
heterogeneous collection of
neurons
scattered throughout the
brainstem
tegmentum
that either modulate
forebrain
and spinal cord activity or coordinate the firing patterns of
lower motor neurons
engaged in reflexive or stereotypical somatic motor and visceral motor activities
reticulospinal tract
descending pathway from the reticular formation of the
brainstem
to spinal
inter-
and motor
neurons
that control anti-gravity posture and locomotion
retina
light-sensitive neuronal layer lining the back of the eye that sends impulses through the optic nerve that are translated into a visual image; part of the
central nervous system
retropulsion
a tendency to walk backward involuntarily that can occur in
Parkinson disease
rhombencephalon
hindbrain; includes the
pons
cerebellum
and
medulla
righting reflex
ability to make postural adjustments in response to perturbations
rigidity
increased resistance throughout the range of motion when passively moving a body part due to co-contraction of agonist and antagonist muscles (“lead pipe”)
ring-enhancement
CT or MRI contrast enhancement surrounding a lesion that has
blood-brain barrier
breakdown, such as metastatic tumor or abscess
Romberg test
inability to maintain upright posture when feet together and eyes closed; indicates impaired
proprioception
root
part of the nerve that branches off from the spinal cord and enters into the
intervertebral foramen
rooting reflex
normal neonatal reflex consisting of turning the head towards a stimulus presented to the side of the mouth, latching on and sucking
Rosenthal fibers
eosinophilic corkscrew or rod-shaped inclusions seen in pilocytic
astrocytoma
rostral
toward the head or nose
rostrocaudal
literally “from the nose to the tail”; used to describe the sequence of symptoms referable to progressively lower parts of the
brainstem
characteristic of
transtentorial herniation
rubral tremor
low-frequency (<4.5 Hz)
tremor
often of irregular, coarse rhythm that is present during both rest and intentional movements and typically follows
cerebellar
outflow pathway lesions
Ruffini corpuscles
thermoreceptors in the skin
saccade
discrete, rapid
conjugate eye movements
from one object to another
saccular aneurysm
spherical outpouching from one side of an artery that occurs at an arterial bifurcation point and reflects weakness of all layers of the vessel wall
sagittal
vertical plane passing through the standing body from front to back
sagittal sulcus (longitudinal fissure)
long, deep, sagittally oriented cleft that separates the two
cerebral hemispheres
on the dorsal midline
salivatory nuclei
small
nuclei
in the pontine
tegmentum
that provide parasympathetic preganglionic innervation to ganglia associated with the lacrimal and salivary glands to control salivation and tearing
scanning speech (ataxic
dysarthria
abnormal staccato-like speech due to a lesion of the
cerebellum
or
cerebellar
pathways
scaphocephaly (dolichocephaly)
premature closure of the
sagittal suture
schizencephaly
developmental birth defect characterized by abnormal slits or clefts in the
cerebral hemispheres
extending from the
cortical
surface to the underlying ventricle
Schwann cell
glial
cell of the
PNS
that forms the insulating
myelin
sheath of peripheral
axons
schwannoma
WHO grade
I benign peripheral nerve sheath tumor occurring commonly in the
cerebellopontine angle
(cranial nerve VII) or in the bony foramina around the spinal cord (spinal nerve root); characterized histologically by Antoni A and Antoni B tissue and Verocay bodies (zones of nuclear palisading)
scintillating scotoma
visual
migraine
aura
consisting of shimmering lights followed by a dark spot or partial loss of vision that may move across the visual field
scotoma
island-like gap or blind spot in the visual field; pleural=scotomata
secondary progressive
clinical course of
multiple sclerosis
that initially is
relapsing-remitting
and then becomes progressive at a variable rate, possibly with an occasional relapse and minor remission
secondary symptoms
symptoms referable to secondary effects of a lesion e.g., edema, blockage of
cerebrospinal fluid
pathways, stretching of vessels
sectoranopia
loss of vision in a wedge of the visual field
seizure
discrete event due to sudden, transient, excessive
neuron
al discharges in the brain
sella turcica
saddlelike prominence on the upper surface of the sphenoid bone of the skull, situated in the
middle cranial fossa
and containing the
pituitary gland
senile plaque
see
neuritic plaque
sensory trick
specific trigger a patient uses to relieve
dystonia
, e.g., touching the outer canthus of the eye to temporarily relieve
blepharospasm
septal nuclei
neuronal structures in the rostral forebrain adjacent to the septum pellucidum that communicate with the
hippocampus
amygdala
hypothalamus
midbrain
habenula
cingulate gyrus
and
thalamus
septum pellucidum
membrane extending ventrally from the body of the
corpus callosum
that separates the two lateral ventricles from each other setting sun sign forced depression of the eyes due to pressure on the dorsal
midbrain
in the setting of
hydrocephalus
; see also
Parinaud’s syndrome
shadow plaque
foci of
myelin
preservation at the periphery of active
multiple sclerosis
plaques thought to represent partial remyelination
sharp wave
EEG
pattern consisting of a transient electrical discharge with a pointed peak and a duration of 70-200 milliseconds that stands out from ongoing background activity; has a strong association with
epilepsy
Shy-Drager syndrome
older term for a variant of
multisystems atrophy
characterized by preferential degeneration of the intermediolateral cell column of the spinal cord and
substantia nigra
producing symmetric
parkinsonism
and
autonomic
failure
sialorrhea
drooling; increased salivation
simple tic
tic involving a limited number of muscles; simple vocal tics are meaningless noises such as grunting or throat clearing; simple motor tics are focal movements such as eye blinking or facial grimacing
simultagnosia
disorder of visual attention characterized by inability to  perceive more than 1 object at a time such that scenes and objects are perceived in a piecemeal manner.; sign of bilateral parieto-occipital damage
single fiber electromyography
electrodiagnostic test in which potentials of muscle fibers innervated by a single
axon
are recorded; normal response is for fibers to be activated with consistent latencies whereas in
neuromuscular junction
disorders, latencies among muscle fibers in a single motor unit are variable (increased
jitter
); most sensitive test for
myasthenia gravis
Sjogren’s syndrome
an autoimmune disorder that prohibits production of tears and saliva
skew deviation
hypertropia
in which the eyes move vertically in opposite directions due to acquired
supranuclear
or vestibulo-ocular disruption
sleep latency
speed of falling asleep
sleep paralysis
temporary (seconds to minutes) inability to move or talk that occurs during sleep-to-wake or wake-to-sleep transitions; one of the symptoms of
narcolepsy
, but also experienced by some non-narcoleptic individuals
slow wave sleep
see
non-REM
sleep
smooth pursuit
smooth following eye movements that maintain fixation
solitary nucleus and tract
sensory
nucleus
of the
medulla
that receives
afferent
taste information from nerves VII, IX and X and mediates the gag, cough,
carotid sinus
and other visceral reflexes
soma
cell body, which contains the nucleus and endoplasmic reticulum
somatic nervous system
portion of the
peripheral nervous system
associated with voluntary control of body movement and relay of sensory input to the
central nervous system
; nerves that connect to skin, sensory organs and skeletal muscles
somatosensory evoked potentials (SSEP)
series of waves that reflect sequential activation of neural structures along the somatosensory pathways following electrical stimulation of peripheral nerves (typically elicited by stimulation of the median nerve at the wrist, the common peroneal nerve at the knee, and/or the posterior tibial nerve at the ankle and recorded from electrodes placed over the scalp, spine and peripheral nerves)
somesthesia
sensation
somnambulism (sleep walking)
arising from bed during a period when there is a simultaneous occurrence of incomplete wakefulness and nonREM sleep; typically occurs in the first third of the night during deep sleep
soporific
causing or tending to induce sleep, such as a hypnotic drug
spasticity
abnormal increase in muscle tone and reflexes, manifested as a velocity dependent spring-like resistance to moving or being moved; indicates an upper motor neuron lesion
spike
EEG
pattern consisting of a transient electrical discharge with a pointed peak and a duration of less than 70 milliseconds that stands out from ongoing background activity; has a strong association with epilepsy
spike-and-wave complex
generalized synchronous pattern seen on
electroencephalogram
, consisting of a sharply contoured fast wave followed by a slow wave; seen in generalized
epilepsy
spina bifida
failure of bone fusion in the posterior midline of the vertebral column resulting in a bony cleft through which the
meninges
and varying quantities of spinal cord tissue protrude
spina bifida occulta
closed
spinal dysraphism
characterized by posterior vertebral defect and various overlying cutaneous anomalies (e.g., lipoma, patch of hair); often associated with other spinal cord abnormalities
spinal accessory nerve (cranial nerve XI)
motor nerve originating partly from the
medulla
nucleus ambiguus
– innervating laryngeal muscles) and partly from the spinal cord (accessory nucleus in the ventral horn of the cervical cord—innervating the sternocleidomastoid and trapezius muslces); lesion results in weakness in turning the head to the opposite side and elevating the shoulder
spinal cord
long tubular structure within the
central nervous system
extending from the
medulla
of the
brainstem
, passing through the
foramen magnum
and continuing to the
conus medullaris
at the 1st or 2nd lumbar
vertebrae
before terminating in the
filum terminale
; functions primarily in the transmission of
afferent
signals from sensory organs to the brain and
efferent
signals from the brain to the
peripheral nervous system
spinal dysraphism
failure of bone fusion in the posterior vertebral column; classified as open (not covered by skin) or closed (covered by skin); see also
meningocele
and
myelomeningocele
spinocerebellar ataxia
group of hereditary neurodegenerative disorders caused by expansion of a CAG triplet repeat and characterized by progressive ataxia and variable other features such as
neuropathy
and hearing or visual loss
spinocerebellar tract
fiber tract originating in the spinal cord and carrying
proprioceptive
input to the
ipsilateral
cerebellum
spinothalamic tract
axonal
tract carrying information on pain and temperature that arises from the posterior nerve roots, which ascend a few segments in Lissauer’s tract before synapsing in the substantia gelatinosa, crossing to the opposite side of the cord in the anterior commisure, and traveling in the anterolateral aspect of the cord up to the
thalamus
and
cortex
splenium
thickened posterior border of the
corpus callosum
spondylosis
degenerative disease of the vertebral column that can result in spinal cord compression
spongiform encephalopathy
progressive neurodegenerative disorder associated with various
prion
agents that produce spongy changes in the brain (e.g.,
Creutzfeldt-Jakob disease
kuru
spreading cortical depression
brief wave of intense
cortical
activation followed by a marked decrease in
neuron
al activity and reduced blood flow that starts in the occipital
cortex
and spreads anteriorally at a rate of 2-6 mm/min; thought to underline
migraine aura
status epilepticus
medical emergency defined as more than 30 minutes of either continuous
seizure
activity or two or more sequential
seizures
without full recovery of consciousness in between
status migrainosus
migraine attack that persists for > 72 hours and often leads to hospitalization
stereognosis
ability to recognize objects by touch
stereotypy
repetitive stereotyped movements commonly seen in tardive dyskinesia,
Tourette syndrome
or autism
stocking-glove
typical distribution on the body where symptoms/signs of peripheral
neuropathy
are evident (toes to knee and fingers to wrist)
strabismus
misalignment of the eyes that is either developmental (due to a miscalibration of the binocular vergence system in the
cerebral cortex
at some point in infancy or childhood) or acquired (due to a
palsy
of a cranial nerve or extraocular muscle)
stria medullaris
white matter
tract connecting the anterior
hypothalamus
and septal
nuclei
in the medial basal
forebrain
with the
habenula
stria terminalis
white matter
tract containing amygdaloid
efferents
to the septal
nuclei
in the medial basal
forebrain
and
nuclei
of the anterior
hypothalamus
striate cortex
see
calcarine cortex
striatonigral degeneration (SND)
older term for a variant of
multisystems atrophy
characterized by degeneration of the
striatum
and the
substantia nigra
producing symmetric
parkinsonism
that does not respond to levodopa or dopamine agonists
striatum
(“striped”) part of the
basal ganglia
consisting of the
caudate
and
putamen
(separated by fibers of the anterior limb of the
internal capsule
stroke
sudden loss of neurological function caused by a blockage or rupture of a blood vessel to the brain or spinal cord; includes
infarction
and hemorrhage subtypes
stupor
condition of unresponsiveness from which the patient can only be aroused by vigorous and repeated stimuli; once stimulus ceases, patient lapses back into unresponsiveness
subacute
developing over days to weeks; suggests an expanding lesion (e.g, tumor or abscess)
subarachnoid hemorrhage
bleeding in the
subarachnoid space
most commonly due to trauma or rupture of an
aneurysm
or
arteriovenous malformation
subarachnoid space
actual space separating the
pia
and
arachnoid
that surround the brain and spinal cord; contains
cerebrospinal fluid
, arteries and veins and filaments of
arachnoid
matter, giving it the appearance of a spider web
subclinical seizure
electrographic seizure without clinical manifestations
subcortical
portion of the brain immediately below the
cerebral cortex
; includes corona radiata,
internal capsule
basal ganglia
and
thalamus
, among others
subcortical leukoencephalopathy
see
Binswanger’s disease
subdural hemorrhage
collection of blood in the subdural space following trauma to small bridging veins or in elderly patients with cerebral atrophy or those with clotting abnormalities
subdural space
potential space between the
dura
and
arachnoid
that can be filled with blood,
cerebrospinal fluid
or pus
subhyaloid hemorrhage
accumulation of blood near the optic disc seen on fundoscopic exam in
subarachnoid hemorrhage
subiculum
division of the parahippocampal
gyrus
adjacent to the hippocampal fissure that is the major source of
efferent
fibers from the hippocampal formation to
rostral
structures in the basal
forebrain
substantia gelatinosa
narrow, dense, vertical band of
gray matter
forming the dorsal part of the posterior column of the spinal cord and serving to integrate the sensory stimuli that give rise to the sensations of pain and temperature
substantia nigra
nucleus
in the
midbrain
tegmentum
that is divided into the pars compacta, a region of compactly organized dopaminergic cells that innervate the
striatum
and
cerebral cortex
, and the pars reticulata, a region containing loosely organized cells that is a pallidal division of the
basal ganglia
and sends its output to the
thalamus
and
superior colliculus
subthalamic nucleus (subthalamus)
nucleus
in the ventral
diencephalon
that modulates the output of the
basal ganglia
from the internal segment of the globus pallidus to the
thalamus
sulcus
groove in the
cerebral cortex
separating two
gyri
superior cerebellar peduncle (brachium conjunctivum)
principle efferent fiber bundle from the
cerebellum
; fibers
decussate
in the
midbrain
and end primarily in the
red nucleus
and
dorsal
thalamus
; lesions of the
caudal
SCP before the decussation result in
ipsilateral
deficits in motor coordination whereas lesions
rostral
to the decussation result in
contralateral
deficits;
afferent
fibers from the ventral
spinocerebellar tract
travel in the SCP to bring
proprioceptive
information from the lower body to the
cerebellum
superior colliculus
paired structures on the dorsal surface of the
rostral
midbrain
that receive unconscious visual input directly from the retina and help orient the head and eyes to all types of sensory stimuli
superior sagittal sinus
venous structure occupying the convex margin of the falx cerebri and draining the upper part of the
cerebral hemispheres
supranuclear
central connections
rostral
to the cranial nerve
nuclei
suprasellar
above the
sella turcica
supratentorial
above the
tentorium cerebelli
, i.e.,
cerebral cortex
thalamus
and
basal ganglia
suture
junction between two bones of the skull: coronal separates the two frontal bones from the parietal bones; metopic separates the frontal bones; sagittal separates the two parietal bones; lambdoid separates the occipital bone from the two parietal bones
Sylvian fissure (lateral fissure or lateral sulcus)
prominent long, deep fissure on the lateral surface of the
cerebral hemisphere
that divides the posterior frontal and anterior parietal lobes from the superior temporal lobe
sympathetic nervous system
part of the autonomic nervous system concerned with preparing the body for fear, fight or flight; preganglionic fibers arise from the lateral horns of the spinal segments T1-L2
symptomatic epilepsy
epilepsy that is due to a known cause (e.g., tumor)
synapse
neuronal junction; site of transmission of electric nerve impulses between two neurons or between a
neuron
and a muscle or gland
syncope
temporary loss of consciousness due to a lack of blood flow to the brain
syndrome of inappropriate ADH secretion (SIADH)
disorder of osmoregulation involving excessive release of arginine vasopressin (antidiuretic hormone), which causes excessive water retention by the kidney, leading to a dilutional hyponatremia; occurs in a wide range of neurological disorders and other medical conditions
synesthesia
condition associated with involuntary perceptual experiences that are elicited by stimuli that would not be expected to elicit such a response — a crossing of sensory modalities, e.g., experiencing colors in response to numbers, letters and words
synucleinopathies
group of neurodegenerative diseases characterized by neuronal or glial inclusions composed of alpha-synuclein; includes idiopathic Parkinson disease and
diffuse Lewy body disease
syringobulbia
central cavitation (cystic lesion) within the spinal cord (syringomyelia) that extends up to the
medulla
and pons
syringomyelia
central cavitation (cystic lesion) of the spinal cord, usually in the cervical region, producing a distinctive cape-like distribution of
spinothalamic tract
sensory loss while leaving the
dorsal columns
relatively intact
tardive
symptoms that develop slowly or appear long after inception, e.g., tardive dyskinesia occurring after chronic exposure to dopamine antagonists
tau
microtubule-associated protein that is functionally modulated by phosphorylation and is hyperphosphorylated in several neurodegenerative diseases.
tauopathies
group of neurodegenerative diseases characterized predominantly by abnormalities of tau protein; includes
frontotemporal dementia
progressive supranuclear palsy
corticobasal degeneration
teardrop fracture
triangular fracture of the anteroinferior aspect of a vertebral body due to axial loading with flexion or extension; often unstable associated with ligamentous injury and/or spinal cord injury
tectospinal tract
descending pathway from
midbrain
tectum to spinal inter- and motor
neuron
s that control anti-gravity posture and locomotion and that probably mediate tonic neck reflexes
tectum
dorsal surface of the
midbrain
that contains the superior and
inferior colliculi
tegmentum
floor of the
midbrain
that contains the
substantia nigra
and the
red nucleus
teichopsia
see
fortification spectrum
telencephalon
anterior portion of the
prosencephalon
, constituting the
cerebral hemispheres
temporal lobe epilepsy
partial
epilepsy
arising from the temporal lobe of the brain
tendon release (tenotomy)
surgical procedure involving division of a severely contracted tendon in the management of
spasticity
tension-type headache
nonspecific headache that is typically dull, aching, and bilateral, and is often described as a tightening band-like sensation around the head or neck; may be related to muscle tightening in the back of the neck and/or scalp
tentorium cerebelli
fold of
dura mater
that covers the
cerebellum
and supports the occipital lobes of the
cerebrum
tetany
repetitive, spontaneous
axonal
discharges at high rates of up to 300 Hz producing intense muscle spasm in the setting of electrolyte or acid-base disturbance
tethered cord
attachment of the spinal cord to the vertebral column or subcutaneous tissues by a thickened
filum terminale
, fibrous band,
diastematomyelia
, dermal sinus tract or lipoma resulting in a low-lying
conus medullaris
(i.e., below the L2-3 interspace)
tetraplegia
see
quadriplegia
thalamus
large ovoid mass of
gray matter
in the dorsal aspect of the
diencephalon
that is located medial to the
internal capsule
and
caudate
and functions as a relay station between the
cerebral cortex
and the
brainstem
and spinal cord
thunderclap headache
sudden onset of severe head pain with neck stiffness that may be associated with altered consciousness or focal neurological deficits; suggests
subarachnoid hemorrhage
tic
repetitive, stereotyped, simple or complex movements that can be voluntarily suppressed for short periods of time (e.g., eye blinking or throat clearing)
tilmus
see
floccillation
time-intensity profile
of the temporal features of a patient’s symptoms that provides clues about etiology of the disease process;
acute
subacute,
recurrent-remittent
or
chronic-progressive
tinnitus
sound experienced subjectively with no external source, most commonly ringing, buzzing or roaring
titubation
tremor
of the head and neck
Todd’s paralysis
temporary (minutes to hours or rarely days) post-
seizure
mono- or
hemiplegia;
indicates
seizure
was focal onset; sometimes term used for other temporary focal post-
seizure
deficits, such as
aphasia
or sensory abnormalities
tolerance
gradual loss of response to a drug with prolonged use
Tolosa-Hunt syndrome
rare painful
ophthalmoplegia
due to a granulomatous inflammation of the
cavernous sinus
paralysis
of the third, fourth, and/or sixth cranial nerves) typically relieved by corticosteroids
tomacula
focal area of
myelin
thickening creating a sausage-like appearance of nerves; common in the genetic
neuropathy
, hereditary liability to pressure palsies
tonic-clonic seizure (grand mal seizure)
generalized seizure
characterized by initial contraction of the muscles (
tonic
phase), which may involve tongue biting and urinary incontinence, followed by rhythmic muscle contractions (
clonic
phase)
tonic neck reflexes
movements and postures of the arm and leg when the neck is bent forwards, backwards, or to the side that are present in normal infants and are incorporated in many bodily movements of normal children and adults
tonic seizure
generalized seizure
that involves stiffening of the entire body
tonsilar herniation
herniation of the
cerebellar
tonsils through the foramen magnum
torsion
see
cyclotorsion
torticollis
form of
dystonia
in which the neck muscles contract involuntarily, causing the head to turn
Tourette syndrome
childhood onset movement disorder characterized by simple or complex
tics
and often associated with obsessions, compulsions and attention deficit disorder
tract
bundle of nerve fibers
transcortical motor aphasia
impairment of language production (
non-fluent aphasia
) sparing repetition due to a lesion in the anterior
extrasylvian
region (prefrontal and medial frontal
cortex
transcortical sensory aphasia
impairment of language comprehension (
fluent aphasia
) sparing repetition due to a lesion in the posterior extrasylvian region (inferior temporo-occipital
cortex
transcutaneous electric nerve stimulation (TENS)
method of pain control involving application of electrical impulses to nerve endings via electrodes that are attached to a stimulator by flexible wires and placed on the skin; thought to block the transmission of pain signals to the brain
transformed migraine
migraine
pattern that has changed from episodic to chronic, often related to the overuse of analgesics (
medication overuse headache
transient ischemic attack
abrupt focal loss of neurologic function caused by reduction in blood flow that persists less than 24 hours and clears without residual disability
transtentorial (central) herniation
downward displacement of the cerebral hemispheres pushing the
diencephalon
and
midbrain
through the
tentorial
notch; symptoms classically follow a
rostrocaudal
deterioration
transverse myelitis
inflammatory disease involving both sides of the spinal cord in which motor and sensory deficits occur below the level of the lesion; occurs commonly in
multiple sclerosis
and various infectious and connective tissue disorders
tremor
involuntary, rhythmic oscillatory movements about a fixed point due to alternating or synchronous contractions of agonist and antagonist muscles; see also
action
essential
intention
physiologic
postural
resting
and
rubral
tremor
trigeminal nerve (cranial nerve V)
mixed sensory and motor nerve made up of ophthalmic, maxillary and mandibular divisions responsible for sensation from the face, oral and nasal cavities, and
supratentorial
dura
(but not posterior scalp) and motor innervation of the muscles of mastication; sensory fibers originate in the gasserian
ganglion
and (1) descend to the upper cervical cord in the spinal tract of V then ascend in the trigeminothalamic tract to the
thalamus
(pain, temperature, touch), (2) enter the main sensory nucleus of V and ascend to the thalamus (tactile and proprioceptive sensation) or (3) enter the mesencephalic
nucleus
(jaw
proprioception
trochlear nerve (cranial nerve IV)
motor nerve innervating the superior oblique muscle, which depresses and intorts the eye; only cranial nerve to exit dorsally and cross the midline before emerging from the
brainstem
— thus a lesion of the
nucleus
(which is in the
caudal
midbrain
) affects the
contralateral
eye
trigonocephaly
premature closure of the metopic
suture
producing bowing of the forehead
triple flexion
spinal reflex consisting of flexion at the hip, knee and ankle in response to stimulation of the sole of the foot; indicates
corticospinal tract
lesion
truncal sensory level
level on the trunk below which sensation is impaired; sign of spinal cord lesion
two-point discrimination
ability to detect two stimuli presented simultaneously at decreasing distance as being two separate stimuli; for normal tactile two-point discrimination, the two points of calipers or a paperclip should be recognized at a separation of 2-4 mm on the lips and finger pads, 8-15 mm on the palms and 3-4 cm on the shins
U fibers
short U-shaped
white matter
tracts that lie just beneath the
cerebral cortex
and connect adjacent
gyri
uncal herniation
displacement of the
uncus
of the temporal lobe and the
hippocampal gyrus
towards the midline and over the lateral edge of the
tentorium
due to an expanding lesion in the lateral
middle cranial fossa
or temporal lobe; earliest consistent sign is an
ipsilateral
dilating pupil due to compression of the ipsilateral third cranial nerve
uncus
most anterior part of the parahippocampal
gyrus
upper motor neuron
1st order
neurons
that remain in the
CNS
and synapse with
lower motor neurons
; lesions result in
spasticity
, hyperreflexia/
extensor plantar response
(upgoing toe)
utilization behaviors
compulsive grasping or using objects that are within reach or in the field of vision; sign of frontal lobe damage
vacuolar myelopathy
vacuolation of
myelin
in the posterior and lateral columns of the primarily thoracic spinal cord occurring in AIDS and resulting in
paraparesis
, sensory
ataxia
and incontinence; resembles the
myelopathy
associated with vitamin B12 deficiency
vagus nerve (cranial nerve X)
nerve containing motor, sensory and
parasympathetic
fibers; motor fibers originate from the
dorsal motor nucleus of the vagus
(to innervate the pharynx and the thoracic and abdominal viscera) and the
nucleus ambiguus
(to innervate the palate, pharynx and larynx); sensory fibers originate in the nodose ganglion and mediate taste and sensation in the pharynx and thoracic and abdominal viscera
vascular dementia
dementia
with a stepwise deteriorating course and a patchy distribution of neurological deficits caused by cerebrovascular disease; includes
multi-infarct dementia
and
Binswanger’s disease
vasospasm
blood vessel constriction in response to irritative stimuli
vegetative state
subacute or chronic condition following
coma
and consisting of return to wakefulness but apparent total lack of cognition
ventral
anterior
ventral horn
see
anterior horn
ventricles
four
cerebrospinal fluid
filled cavities (paired lateral, third and fourth) deep with the brain that communicate with each other and with the central canal of the spinal cord and the
subarachnoid space
vergence
movement of the eyes in opposite directions so that images of an object are placed on both
foveas
and thus appear single
vergence (dysconjugate eye movements)
movement of both eyes in different directions at the same time; includes 2 types: convergence and divergence
vermis
median region of the
cerebellum
lying between the cerebellar hemispheres
version (conjugate eye movements)
movement of both eyes in the same direction at the same time; includes 4 types:
saccade
smooth pursuit
optokinetic nystagmus
movements and
vestibulo-ocular response
movements
vertebrae
series of 33 bones comprising the spinal column divided into 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral and 3-5 coccygeal; each vertebra consists of a body, arch and multiple processes
vertebral artery
paired arteries that arise from the subclavian arteries and fuse to form the
basilar artery
on the ventral surface of the
brainstem
; supply blood to the lower brainstem and posterior
cerebellum
vertigo
subjective sense of imbalance usually noted as an illusion of moving or spinning of the external world
vestibulocochlear nerve (cranial nerve VIII)
sensory nerve carrying information from the semicircular canals, utricle and saccule to mediate equilibrium and hearing
vestibulo-ocular response
see
oculovestibular response
vestibulospinal tract
descending pathway from vestibular
nuclei
in the
brainstem
to spinal
inter-
and motor
neurons
that causes contraction of many muscles in the trunk and limbs as the head moves in space, providing automatic anti-gravity control to maintain upright stance
vicariation
process by which adjacent or remote
cortex
may assume the function previously carried out by damaged
cortex
Virchow-Robin Spaces
perivascular extensions of
subarachnoid space
visual acuity
measurement of the eye’s ability to distinguish details; typically expressed as a fraction in which the numerator (20) indicates that the subject is standing at 20 feet from a normal test object and the denominator is the distance from which a normal subject can read the same normal image .
visual evoked potentials (VEP)
series of waves that reflect sequential activation of neural structures along the visual pathways following checkerboard stimulation; most useful in screening for
optic nerve
pathology (e.g.,
optic neuritis
) and less useful in postchiasmatic disorders
visual fields
entire area visible to an eye that is fixating straight ahead
(cataplexy
sleep paralysis
hypnagogic hallucinations
and an abnormal tendency to pass directly into REM sleep from wakefulness)
Wallenberg syndrome
see
lateral medullary syndrome
Wallerian degeneration
stereotyped degenerative reaction of
axons
and
Schwann cells
distal to a site of mechanical damage; occurs simultaneously in many of the
axons
in a
fascicle
watershed infarct
(aka borderzone infarct)
infarct
occurring in tissue that is in the distalmost territory of two arteries and thus vulnerable to a reduction in blood supply; may be a result of global hypoperfusion or local atherosclerotic disease
wearing off phenomenon
waning of the effects of a dose of levodopa prior to the scheduled time for the next dose, resulting in decreased motor performance
Weber Syndrome
ipsilateral
oculomotor
palsy and
contralateral
hemiplegia
due to
ventral
midbrain
lesion affecting the III nerve
fascicles
and
cerebral peduncle
wet keratin
nodules composed of often calcified stacks of keratin characteristic of
craniopharyngioma
Wernicke’s aphasia
see
fluent aphasia
Wernicke’s encephalopathy
syndrome of confusion/short-term memory loss,
ophthalmoplegia
(especially abducens palsy), and ataxia due to thiamine deficiency, occurring in the setting of alcoholism, starvation or protracted vomiting; may progress to
coma
if untreated; associated with neuronal damage that is most prominent in the
mammillary bodies
inferior colliculus
and
thalamus
West’s syndrome
epilepsy
syndrome characterized by
infantile spasms
, mental retardation, and
hypsarrhythmia
on
EEG;
begins before 1 year of age
white matter
part of the
CNS
that contains
axons
WHO grade
scheme for grading
central_nervous_system
neoplasms histologically developed by the World Health Organization
Grade
Benign
II
Low grade (atypia only)
III
Intermediate grade (mitotic activity)
IV
High grade malignant (necrosis or endothelial proliferation,
typically with atypia and mitosis)
xanthochromia
yellowish discoloration of
cerebrospinal fluid
resulting from lysis of red blood cells seen ~ 12 hours to 2 weeks after
subarachnoid hemorrhage
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