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abducens nerve (cranial nerveVI) 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 &
because of their long course arevulnerable to damage by mass
lesions/increased intracranial
pressure
abduct move away fromthe saggittal plane of the body
absence seizure (petit malseizure) generalized
seizure characterized by abrupt
cessation of ongoing activity with
a blank stare & lost or impaired
consciousness lasting on average10-20 seconds
abulia loss of will, impulse, &decision-making ability
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acalculia "inability to calculate"or difficulty with arithmetic; may
be the result of damage to
the angular gyrusin
the hemisphere dominant for
speech & language
acephalicmigraine migraine variant
consisting of the migraineaura without the headache; also
known as migraine
equivalent accommodation adjust
ment of the focal length of the lens
of the eye in order to keep objects
at varying distances in focus onthe retina
acrocephaly actionpotential see brachycephaly
action potential rapid, transient,all-or-none nerve impulse initiatedat the axon hillock; electrical
signal by which the brain receives,
analyzes, & conveys information
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action tremor tremor that appearsduring movement of the affected
body part
activities of daily living(ADLs) activities a person
performs for self-care (feeding,
grooming, bathing, dressing),
work, homemaking, & leisure;
ability to perform ADLs is oftenused as a measure of
ability/disability
activity limitations difficulties anindividual may have in executing
specific tasks or actions (e.g.,
walking independently).
acute developing over minutes tohours; implies acute metabolic
dysfunction
(e.g., ischemia, seizure )
Acute DisseminatedEncephalomyelitis(ADEM) acute, classically
monophasic demyelinative disease
of theCNS that may follow a viral
syndrome or vaccination or no
identifiable predisposing cause
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adduct move towardsthe saggittal plane of the body
Adies syndrome associationof Adies tonic pupil with absence
of muscle stretch reflexes
Adies tonic pupil irregularlydilated pupil exhibiting minimal or
no reaction to light, slow reaction
to accommodation, &hypersensitivity to pilocarpine;
typically idiopathic & most often
seen in young women
adrenoleukodystrophy typicallyX-linked
recessive demyelinative disease
adrenal dysfunction due to
accumulation of very long chain
fatty acids
afferent sensory pathwayproceeding toward the CNS fromthe peripheral receptor organs
afferent pupillary defect
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(Marcus-Gunn pupil) pupillarydilation 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 &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 tocommunicate ideas in written
language not due to mechanical
dysfunction; typically results fromdamage to the parietal lobe.
akathisia motor restlessness;inability to sit still
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akinesia paucity ofmovement akinetic
mutism disorder of consciousness
characterized by periods of sleep
& periods of wakefulness during
which the patient lies with eyes
open but is unresponsive, mute, &
immobile; often due to frontal lobedamage
alexia inability to read, usuallydue to a lesion of dominant
occipitotemporal cortex
alien hand syndrome syndromecharacterized 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 seenin corticobasal
degeneration allodynia condition
in which an ordinarily painless
stimulus is experienced as being
painful
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alpha motor neurons largemotor neurons that innervate
extrafusal skeletal muscle
fibers alpha-synucleinprotein
expressed predominantly in
the CNS that when aggregated,
can result in neurodegenerative
diseases such as Parkinsondisease, dementia with Lewy
bodies, & multisystems atrophy
Alzheimers disease mostcommon cause of dementia in
older adults; a neurodegenerative
disease characterized by thegradual loss of cognitive ability in
association with the
neuropathological findings of
abnormal protein aggregates
(neuritic plaques & neurofibrillarytangles) & neuron loss in
the cerebral cortex
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amaurosis fugax temporary lossof vision in one eye due to
impairment of blood supply
through the internal carotid
artery or the ophthalmic artery
amblyopia developmentalabnormality 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 & the
regulation of autonomic processes;
part of the limbic system
amyotrophic lateralsclerosis (Lou Gehrigs disease)
inexorably progressive & fatal
disease of unknown causecharacterized by slowly
progressive degeneration
of upper & lower motor neurons
analgesia loss of pain sensation
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anencephaly(aprosencephaly) CNS malformat
ion involving failure of closure of
the cephalic end of the neural tube,
resulting in absence of
the forebrain & cerebrum;
rudimentary brainstem may be
present so that reflex actions such
as breathing & responses to soundor 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 locatedimmediately posterior to the
supramarginal gyrus at the
superior edge of the temporal lobe
& involved in recognition ofvisual symbol; lesions can result
in alexia & agraphia
anhidrosis absence of sweating anisocoria pupillary asymmetry
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ankle-foot orthosis (AFO) bracethat is worn on the lower leg &
foot to support the ankle & correct
foot drop
anomia inability to name objectsor to recognize written or spoken
names of objects
anosmia loss of sense of smell anosognosia lack of awareness of
or indifference to ones own
neurological deficit, seen with
nondominant parietal lobe lesions
anterior cerebral artery a branchof the internal carotid artery;
supplies blood to the medial aspect
of thecerebral cortex (leg area
predominant), some areas of the
frontal lobe, corpus
callosum, caudate, & the anterior
limb of the internal capsule
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anterior commissure one of thethree major groups of commissural
fibers that courses through
the basal ganglia & cross the
midline in the anterior forebrain to
interconnect the olfactory
bulbs, amygdala,
&hippocampal areas, among
others anterior communicating
artery branch of the internal
carotid artery that joins together
the paired anterior cerebral arteries
anterior cord syndrome spinalcord 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, bladderdysfunction, & loss of pain
sensation below the level of the
lesion
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anterior cranial fossa portion ofthe internal base of the skull
housing the frontal lobes
anterior horn (ventralhorn) gray matter in the front of
the spinal cord that
contains motor_neurons
Anton's syndrome formof cortical blindness in which thepatient 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 disorderedexpression or comprehension of
spoken &/or written language
caused by brain injury; see
also non-
fluent, fluent, conduction, global, transcortical motor, & transcortical
sensory aphasia
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aphemia inability to speak wordsdespite being able to make other
sounds
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 impairedplanning/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 butpreserved ability to perform
bicycling movements of the legs
while lying in bed). Results from
dissociation of parts of
the cerebrum& is often associated
with parietal lobe lesions.
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aprosencephaly see anencephaly arachnoid middle layer of
the meninges covering the brain &
spinal cord
arachnoidgranulations (arachnoid villi)
branched tufts of arachnoid thatproject through the dura mater into
the venous sinuses & function to
return CSF to the systemic
circulation
arachnoid villi diverticula ofthe arachnoid mater in
the subarachnoid space that extend
into the veins & venous sinuses of
the dura; a major pathway for the
drainage of cerebrospinal fluid &
transport across the endotheliuminto the blood.
arcuate fasciculus pathwayconnecting Wernickes area in the
posterior left superior
temporal gyrus to Brocas area in
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the left inferior frontal lobe; lesion
results in impaired repetition
area postrema chemoreceptortrigger zone for vomiting that is
located on the dorsal surface of
the medulla
Argyll-Robertson pupil pupilexhibiting light-near
dissociation due to a lesion inthe midbrain periaqueductal
gray matter caused by tertiary
syphilis arousal abrupt change
from sleep to wakefulness, or from
a "deeper" stage of non-REM
sleep to a "lighter" stage
arteriovenous malformation atangled collection of abnormal
arteries & veins
arteritis inflammation of an artery arthrokineticnystagmus nystagmus induced by
passive rotation of the arm of a
stationary subject seated in total
darkness inside a rotating drum
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ascending tract of Deiters directpathway (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 syndromecharacterized by headache, neckstiffness, low grade fever,
& Cerebro Spinal
Fluid lymphocytic pleocytosis in
the absence of an acute bacterial
pathogen; often usedsynonymously with
viralmeningitis, 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; & various
systemic disorders
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asomatognosia inability torecognize part of ones own body,
seen with nondominant parietal
lobe (or less commonly premotor
cortex) lesions
associated reactions movementsof body parts other than the ones
that are intended to move, oftenincreased with increased effort
association cortex cortical areasinvolved in higher order
processing of sensory information
& integration of multiple sensory
& sensorimotor
modalities astasia inability to
stand because of motor
incoordination
astasia-abasia functional stance &gait characterized by bizarremovements, typically swaying
wildly & nearly falling, but then
recovering at the last minute
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asterixis sudden palmar flappingmovement of the hands at the
wrists; indicative of
metabolic encephalopathy
astrocytes CNS glia that functionto orient neuroblast migration in
the cerebral
& cerebellar hemispheres, providemechanical support, react to
injury, insulate synaptic surfaces,
provide a source & sink for
extracellular potassium, & uptake
neurotransmitters to terminate
their synapticaction astrocytoma most
common central nervous
system tumor derived
from astrocytes astrocytosis reacti
on of astrocytes to neuronal injurycharacterized by an increase in the
number & size of astrocytes
(primary reaction) & cytoplasmic
changes including increased glial
filaments & glassy eosinophilic
cytoplasm followed by formation
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not under conscious control (e.g.,
heartbeat, breathing, sweating)
autonomic nervous system partof the peripheral nervous
system that regulates visceral
function & homeostasis
independent of voluntary control
autoregulation physiologicalprocess by which blood vesselschange 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 fromthe 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 & its myelin sheath;
preferentially involves the distal
portion of the axon ("dying
back neuropathy")
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axonalspheroid stereotypic axonal respo
nse to injury consisting of marked
swelling due to accumulation of
materials
undergoing axonal transport
measurement of the eyes abilityto distinguish details; typicallyexpressed as a fraction in which
the numerator (20) indicates that
the subject is standing at 20 feet
from a normal test object & the
denominator is the distance fromwhich a normal subject can read
the same normal image . entire
area visible to an eye that is
fixating straight ahead
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Babinski response extension ofthe great toe on stimulation of the
sole of the foot, signifying a lesion
of thecorticospinal tract (a.k.a.,
upgoing toe); see also plantar
response
Balint syndrome syndromecomprising paralysis of visual
fixation, optic ataxia,& impairment of visual fixation
due to bilateral lesions of the
parietal & occipital lobes
basalganglia large subcortical nuclear
masses consisting of
the caudate, putamen, globus
pallidus,subthalamus, & substantia
nigra; part of the motor system
that permits chosen & inhibits
unwanted movement basalpalisading basal layer of small
cells with darkly staining nuclei &
little cytoplasm seen in the
epithelium of craniopharyngiomas
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basilarartery large brainstem artery
located on the ventral surface of
the pons formed by the joining of
the two vertebral arteries &
bifurcating into the posterior
cerebral arteries; supplies blood to
cerebral circulation & ventral pons
basilar migraine formof migraine characterized by avisual aura followed by an often
occipital headache & one or more
of the following
symptoms: dysarthria, vertigo, tinn
itus, decreased hearing, diplopia,blindness,ataxia,
bilateral paresthesia,
bilateral paresis, & impaired
cognition
behavioral symptom complexchanges in personality & behavior
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Bells palsy(idiopathic facial paralysis) crani
al 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, & impairedlacrimation
Bell's phenomenon fluttering ofthe eyes upward when closed
eyelids are opened by the
examiner
BenediktSyndrome ipsilateral oculomotor
palsy
& contralateral hemichoreoathetos
is due to lesion of
theventral midbrain tegmentum affecting the IIII nerve fascicles &
the red nucleus
Berry aneurysm small saccularaneurysm of an intracranial artery
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Binswangers disease(subcortical
leukoencephalopathy) degenerati
ve white matter disease
producingdementia due to
hypertensive microvascular
changes lipohyalinosis of the small
arteries & fibrinoid necrosisof thelarger vessels inside the brain)
blepharospasm excessiveinvoluntary contraction of the
orbicularis oculi sometimes
resulting in functional blindness; a
focal dystonia
blood-brain barrier specializedsystem of capillary endothelial
cells that strictly limits transport
into the brain through both
physical (tight junctions) &metabolic (enzymes) barriers
borderzone infarct see watershedinfarct
brachial relating to the arm
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brachium anatomical structurecomprising a collection
of axons that resemble an arm
brachiumconjunctivum see superior
cerebellar peduncle
brachium pontis see middlecerebellar peduncle
brachycephaly(acrocephaly) premature fusion of
bilateral coronal sutures producing
a foreshortened skull
bradykinesia slowed movementdue to dysfunction of the basal
ganglia & related structures
bradyphrenia slowing of thoughtprocesses that can occur
in Parkinson disease or as a side
effect of antipsychotic medications
brain death see death byneurological criteria
brainstem medulla, pons,& midbrain
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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 & measured by surface
electrodes placed at the vertex ofthe scalp & ear lobes; provides
information regarding auditory
function & hearing sensitivity &
used to screen for retrocochlear
pathology (e.g., acousticneuroma),
universal newborn hearingscreening, & intraoperative
monitoring
brain death Brocas aphasia see non-fluent
aphasia Brodmann's areas distinct
regions of the cerebral
cortex recognized by variations in
cell size, density, & thickness of
the cortical layers
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Brown Sequard syndrome spinalcord injury syndrome associated
with damage to one lateral half of
the spinal cord (spinal
hemisection) resulting
in ipsilateral weakness & loss of
vibration proprioception &contrala
teral loss of pain sensation
Brudzinskis sign involuntaryflexion of the hips in response topassive flexion of the neck;
indicative ofmeningeal irritation
bruxism grinding one's teethwhile asleep
bulbar pertaining to the lowercranial nerve nuclei
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burst fracture compressionfracture of vertebral body with
expansion in sagittal & coronal
planes due to axial loading;
unstable & often associated with
spinal cord injury measurement of
the eyes 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 & the denominator is
the distance from which a normal
subject can read the same normal
image .entire area visible to an eyethat is fixating straight ahead
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calcarine cortex primaryvisual cortex located in the
occipital lobe (striate area 17)
carotid sinus arterial baroreceptorlocated at the bifurcation of the
external & internal carotid arteries
that regulates arterial pressure &
heart rate in response to changes in
stretch & transmural pressure carphologia see floccillation catamenial referring to menses;
with regard to women
with epilepsy or migraine, a
tendency forseizures/migraines to
occur around the time of menses
cataplexy sudden loss of posturaltone, often triggered by an
emotional stimulus & resulting in
falls to the floor; seen
in narcolepsy
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cauda equina (horses tail)collection of intradural spinal
nerve roots
caudal to the spinal cord thatsupply the lower limbs & 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 (cavernousmalformation) vascular
malformations composed
primarily of large venous channels
without a clear-cut arterial
component
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cavernous sinus paired, venousstructures located on either side of
the sella turcica that receive blood
from the superior & inferior
orbital veins & drain into the
superior & inferior petrosal
sinuses; contains thecarotid
artery & its sympathetic plexus,the oculomotor nerves (III, IV,
VI), & the ophthalmic branch of
V; lesions typically result
in ophthalmoplegia, orbital
congestion, & proptosis
centralchromatolysis regenerative
response to axonal injury
consisting of neuronal swelling,
nuclear eccentricity, & loss of
Nissl substance
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central cord syndrome spinalcord 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, & avariable degree of sensory loss
below the level of injury
central herniation downwarddisplacement of the cerebral
hemispheres pushing
the diencephalon &midbrain through the tentorial notch; symptoms
classically follow a rostrocaudal
deterioration
central nervous system(CNS) brain & spinal cord
central pain syndrome intensepain arising from injury to
the central nervous system, most
often in patients who have had
a stroke, multiple sclerosis, or
brain injury.
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central sulcus prominent sulcuson the dorsolateral aspect of
the cerebral hemispheres formed
by the precentral &
postcentral gyri; defines the
boundary between the frontal &
parietal lobes centrum semiovale expansive
region of white matter in the
dorsal core of the frontal &
parietal lobes, named because of
its central position in
the forebrain & its semi-ovalshape
cephalic relating to the head cerebellar peduncle three
major white matter structures
containing #efferent & afferent axons of thecerebellum; named the
inferior, middle, &
superior cerebellar peduncles
cerebellar tonsil lateral portionsof the uvula located in the
posterior lobe of the cerebellum
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cerebellopontine angle spacelocated at the junction of
the cerebellum, pons,
& medulla containing cranial
nerves V-XI, blood vessels,
the flocculus of the cerebellum, &choroid plexus
cerebellum brain structurein posterior fossa that coordinates
the many muscles active in any
given movement; receives input
from spinal cord & cerebralcortex & projects to postural &
voluntary motor control systems
& red nucleus
cerebral amyloid angiopathy(congophilicangiopathy) vascular disorder in
which beta amyloid protein is
deposited within the media &
adventitia of small- to medium-
sized meningeal & cortical blood
vessels, causing them to become
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brittle & break; important cause of
predominantly lobar intracerebral
hemorrhage in the elderly
cerebral aqueduct portion of theventricular system that lies in the
dorsal midbrain & connects the
third & fourth ventricles
cerebralarteriosclerosis thickening &hardening of the arteries within the
brain
cerebral atherosclerosis build-upof fatty deposits in the inner wall
of cerebral arteries; form
of cerebral arteriosclerosis
cerebral atrophy the shrinking ofthe brain or brain cells.
cerebral autosomal dominantarteriopathy
with subcortical infarcts &leukoencephalopathy
(CADASIL) familial arterial
disease of the brain caused by
mutations in the Notch3 gene &
consisting of
recurrent subcortical strokes starti
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ng in midadult life, dementia,
depression, & migraine
cerebral cortex highly convolutedlayer of gray matter that
constitutes the outermost layer of
the cerebrum& is responsible for
integrating sensory impulses & for
higher intellectual functions
cerebral hemisphere symmetricalhalf of the cerebrum as separatedby the sagittal sulcus & containing
thecerebral cortex, basal
ganglia, hippocampus,
& amygdala
cerebral peduncle (cruscerebri) white matter tracts
(corticospinal & corticobulbar) on
the ventral surface of
the midbrain containing
the efferent axons of cerebralcortex that project to brainstem &
spinal cord
cerebral perfusion pressure(CPP) mean arterial pressure
(MAP) intracranial pressure
(ICP)
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cerebral salt wasting centrally-mediated hypovolemic
hyponatremia associated with
negative sodium balance that
occurs in approximately 30-50%
of patients with subarachnoidhemorrhage despite their being
given maintenance volumes of
fluids; excessive sodium loss is
thought to be due to impaired
sodium reabsorption in the
proximal tubule & may be causedby disruption of sympathetic input
to the kidneys, production of a
circulating natriuretic factor, or
both
cerebritis inflammation of thebrain
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cerebrospinal fluid (CSF) clear,colorless fluid bathing the entire
surface of the CNS, most of which
is secreted by the choroid
plexus & the remainder by brain
capillaries; flows through theventricles & out into
thesubarachnoid space via the
foramen of Magendie in the
midline & the two foramina of
Luschka at the lateral margins of
the roof of the 4th ventricle, thenis absorbed through the arachnoid
villi in the walls of dural sinuses &
returned to the systemic
circulation
cerebrum anteriorportion of thebrain consisting of the
two cerebral hemispheres that each
contain four lobes
Charcot-Bouchardaneurysm aneurysmal dilation of
small intraparenchymal vessels
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commonly seen in the brains of
patients with hypertensive
hemorrhage
Charcot joint progressivedestruction & deformity of bone &
soft tissue at weight bearing joints
due to severe sensory orautonomic neuropathy cheiro relat
ing to the hand
Chiarimalformation CNS disorder
characterized
by cerebellar elongation &protrusion through the foramen
magnum into the cervical spinal
cord. Type I consists
of caudal displacement of
the medulla & inferior pole ofthe cerebellar hemispheres through
the foramen magnum. Type
II=type I + hydrocephalus &
lumbosacralspina bifida. Type III
involves herniation of the
entire cerebellum through the
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foramen magnum with a
cervicalspina bifida cystica. Type
IV involves cerebellar hypoplasia
chorea involuntary, irregular,rapid, jerking movements
choroid plexus intraventricularstructure thatsecretes cerebrospinal fluid
choroid plexuspapilloma 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 inthe cerebellopontine angle
chronic daily headache headachedisorder consisting of frequent
headache occurring 15 or more
days per month & including
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headache associated with
medication overuse
chronic paroxysmalhemicrania indomethacin-
responsive headache disordercharacterized by the occurrence of
multiple daily attacks lasting 5 to
30 minutes of severe unilateral
head pain often associated
withautonomic phenomenon (eye
tearing, eye redness, eyelid edema,nasal congestion, runny nose); also
known as atypical cluster
headache
chronic-progressive developingover months to years; impliesgradual deterioration as occurs
with degenerative diseases
like Alzheimer
disease, Huntington disease, etc.
cingulategyrus cortical component of
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the limbic system located on the
medial aspect of the hemisphere
superior to the corpus callosum;
involved in emotional & cognitive
processing
cingulate herniation horizontaldisplacement of a cerebralhemisphere due to an expanding
lesion that forces the cingulate
gyrus under the falx
cerebri, compressing the internal
cerebral vein &
the contralateralhemisphere 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
twointernal carotid arteries &
the basilar artery come together,
allowing blood to be redistributed
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to the anterior,middle,
& posterior cerebral arteries
classic migraine see migrainewith aura
ClaudeSyndrome ipsilateral oculomotor
palsy & contralateral ataxia &hemichoreoathetosis due to
adorsal midbrain tegmental lesion
affecting the III
nerve fascicles, superior cerebellar
peduncle, & red nucleus
claustrum thin plate of graymatter lying in the white
matter between the insula &
the basal ganglia that
modulates cortical activity
clay shovelers fracture typicallystable fracture through a spinousprocess due to hyperextension
injury
clonic seizure generalizedseizure characterized by jerking
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movements on both sides of the
body
clonus rhythmic contractionrelaxation tremor due to cyclic
alternations of the spindle stretch
reflex & theGolgi tendon
organ reflex; indicative of
exaggerated stretch reflexes cluster headache primary
headache syndrome characterized
by intense, unilateral orbital,
supraorbital, &/or temporal pain
lasting 15-180 minutes &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
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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 & found at
the junction between gray
matter & white matter where they
are trapped by the acute anglebranching of the microvasculature
cogwheeling ratchety movementdue to superimposition
of tremor on rigidity
coital headache indomethacin-responsive headache disordercharacterized by sudden, severe,
throbbing, occipital headache that
occurs just before or during
orgasm
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cold calorics see oculovestibularresponse
coma state of unarousableunresponsiveness with closed
eyes, no speech, & no purposeful
movements
common carotid artery arterythat arises from thebrachiocephalic artery on the right
& from the aortic arch on the left,
ascending in the neck & dividing
at the upper border of the thyroid
cartilage into the external
&internal carotid arteries to supply
the head & neck
common migraine see migrainewithout aura communicating
hydrocephalus blockageof CSF flow outside the
ventricular system, either at the
level of the arachnoid
granulations or because of
overproduction of CSF (e.g., from
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a choroid plexus papilloma) that
exceeds the rate of absorption
complex partial seizure partialseizure in which consciousness or
awareness is impaired; epileptic
discharge either originates
in limbic structures (hippocampus)
or spreads to them from neocortex,
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 arecoordinated or sequential patterns
of movement such as twirling a
pencil or touching other people
concussion traumatic closed headinjury that results in temporaryimpairment of neurological
function, e.g., transient loss of
consciousness
conduction aphasia selectiveimpairment of the ability to repeat
due to a lesion of the arcuate
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fasciculus, which connects
Wernickes area to Brocas area
conduction block failure ofimpulse conduction along an
anatomically intact axon;
characteristic
ofdemyelinating neuropathy
contracoup opposite to the site ofimpact
contracture permanent shorteningof the muscles & tendons adjacent
to a joint, which can result from
severe spasticity & interferes with
normal movement around the
affected joint
contralateral located on theopposite side of the body (brain)
contusion edematous brain lesioncontainingpunctuate parenchymal hemorrhag
es on the surface of the brain that
may extend bidirectionally into
the white matter &
the subdural & subarachnoid
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spaces; occur at the site of impact
(coup contusion) with direct
trauma & at a site opposite to the
site of impact
(contracoupcontusion) with
acceleration/deceleration injury
conus medullaris caudal-mostpart of the spinal cord located
between the first & second lumbar
vertebrae. Since this structure is
part of the spinal cord but is in
close proximity to spinal nerveroots, lesions often produce
both upper motor neuron & lower
motor neuron deficits
convergence coordinated inwardmovement of the eyes in order tofixate on a near
object convergence-retraction
nystagmus form
of nystagmus consisting of jerking
eye movements inward &
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backward; associated with
dorsal midbrain lesion
coprolalia uncontrolled, oftenobsessive use of obscene language
occasionally seen in Tourette
syndrome
coronal vertical plane from headto foot & parallel to the
shoulders corona radiata fan-like
arrangement of fibers projecting
from all aspects of the cerebral
cortex & converging towardthe thalamus where they will form
the internal capsule
corpus callosum large fiberstructure that makes connections
between homotopic regions ofthe 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 see striatum
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cortical referring to the cerebralcortex, the outermost layer of
the cerebrum
cortical blindness apparent lackof visual functioning in spite of
anatomically & structurally intact
eyes due to bilateral lesions of the
primary visual cortex
corticobasaldegeneration progressiveneurological disorder
characterized by nerve cell loss in
the cerebral cortex & basal
ganglia &
producing parkinsonism, dementia
, visual-spatial impairment, alien
hand syndrome, apraxia,
& myoclonus
corticobulbartract axons originating in theposterior frontal lobe & projecting
to lower motor neurons in
the brainstem
corticospinal tract (pyramidaltract) motor pathway responsible
for voluntary movement that arises
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from primary motor cortex, area 6,
& somatosensory cortex &
descends through the corona
radiata, internal capsule, cerebral
peduncle,
medullary pyramid (where it
decussates), & 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 cellsoccurring in herpes
simplex encephalitis Cowdry B
inclusion bodies large glassy
eosinophilic nuclear inclusions
occurring in herpes
simplex encephalitis
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craft palsy dystonia occurring inthe setting of a highly learned
skilled task, e.g., writers cramp,
yips in golfers
craniectomy surgical removal of asection of bone (bone flap) fromthe 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 theprocedure
craniopharyngioma suprasellarWHO grade I tumor of
children/young adults that causes
significant morbidity & mortality;characterized histologically by
basal palisading, wet keratin, &
infiltrative fingers of tumor that
make it difficult to
cure cranioplasty surgical repair
of a defect or deformity of the
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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 prematureclosure at birth of one or more
cranial sutures, which limits head
growth perpendicular to
the suture(s); seealso brachycephaly, oxycephaly, p
lagiocephaly, scaphocephaly,trigo
nocephaly
craniotomy surgical removal of asection of bone (bone flap) fromthe 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
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creatine to phosphocreatine & is
released into the blood by
tissuesparticularly musclethat
consume adenosine triphosphate
(ATP) rapidly; elevated levels are
seen in myopathy
cremasteric reflex superficial(cutaneous) reflex elicited by
stroking the superior & medial
part of the thigh in a downward
direction; normal response is
contraction of the cremastericmuscle that pulls up the scrotum &
testis on the side stroked;
dependent on nerve roots L1 & L2
Creutzfeldt-Jakobdisease fatal prion diseasecharacterized by spongiform
changes in the brain,
progressivedementia, psychiatric
changes, & myoclonus; form
of spongiform encephalopathy
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crossed adductor reflex reflexcontraction 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 slightjarring of the pelvis
crural relating to the leg cruscerebri see cerebral peduncle
cryptogenic occurring withoutknown cause; in the context
of epilepsy, indicates cases in
which a lesion & distinct
pathogenesis are presumed
cyclotorsion (a.k.a. torsion):rotation of the eye around an
anterior-posterior axis;see excyclotorsion,incyclotorsion
corticobasaldegeneration measurement of the
eyes ability to distinguish details;
typically expressed as a fraction in
which the numerator (20) indicates
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that the subject is standing at 20
feet from a normal test object &
the denominator is the distance
from which a normal subject can
read the same normal image
. entire area visible to an eye that
is fixating straight ahead
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Dawsonsfingers ovoid demyelinating lesio
ns with their long axis
perpendicular to the ventricular
surface seen in multiple sclerosis
death by neurologicalcriteria irreversible loss of all
brain function
decerebrate rigidity stereotypedposture consisting of extension ofall four limbs occurring with
transaction between the superior
collicui & inferior colliculi in
the midbrain; often used
synonymously with extensor
posturing
decorticate rigidity stereotypedposture consisting of flexion of the
forelimbs & extension of the
hindlimbs occurring withtransaction between
the diencephalon & midbrain;
often used synonymously
with flexor posturing
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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 phasesyndrome circadian
rhythm disorder in which in thedaily 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 statecharacterized by disorientation,
inattention, confusion, fear,
irritability, perceptual disturbance,
& fluctuating level of
consciousness; common with toxic& metabolic disorders & acute
febrile systemic infections
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dementia acquired & sustainedloss of memory & other
intellectual functions that is of
sufficient severity to interfere with
daily functioning dementia
pugilistica chronic
traumatic encephalopathy caused
by cumulative & repetitive head
trauma & manifestingas dementia & parkinsonism
demyelination destruction or lossof the myelin sheath
surrounding axons; results in
impaired nerve impulse
conduction
dendrite receiving portion ofthe neuron
denervation loss of nerve supply dermatome distribution of
sensory innervation on the skin ofthe body & the limbs
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diabetes insipidus inability toconcentrate urine resulting from
decreased secretion of antidiuretic
hormone; reflects a lesion of
the hypothalamic osmoreceptors,
supraoptic or
paraventricular nuclei, or the
supraopticohypophyseal tract &may occur in transtentorial
herniation due to downward
traction on
thehypothalamic median eminence
diaphragmasellae thin dural membraneoverlying the sella turcica that is
fenestrated to allow passage of the
infundibulum
diaschisis depression ofmetabolism at sites distant from,but connected with, a site of
cerebral injury (e.g.,infarction) due
to interruption
of afferent or efferent fiber
pathways
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diastematomyelia longitudinaldivision of the spinal cord by a
septum of bone
diencephalon thalamus, hypothalamus, subthalamic nucleus,
& pineal
diffuse axonal injury widespreaddamage to white matter due to
rotational shearing forces withhead trauma
diffuse Lewy body disease (Lewybody dementia) form
of dementia associated with
fluctuating alertness, recurrent
visual hallucinations,
& parkinsonism & defined
pathologically by cortical (as well
as nigral) Lewy bodies
diplegia see paraplegia diplopia double vision dissociated sensory
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deficit impairment ofpain/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 dolls
phenomenon see oculocephalic
response
dorsal posterior dorsal
columns ascending axonal tract
running in the dorsal funiculus of
the spinal cord that carries tactile
&proprioceptive information to
the brain; fibers cross in theventromedial medulla to become
the medial lemniscus dorsal
horn see posterior horn
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dorsal motor nucleus of thevagus parasympathetic nucleus
that stimulates secretion from
glands of the pharynx & thoracic
& abdominal viscera
dorsal rhizotomy surgicalprocedure involving sectioning of
the dorsal spinal nerve roots
performed to reducespasticity dorsal root ganglion collection of
cell bodies located in the
intervertebral foramina that
transduce sensory information into
neural signals & transmit these
signals to the CNS
dose failure phenomenon inwhich an individual dose of
medication has no effect; occurs
in Parkinson diseasepossibly in
association with a tablet gettingstuck in the throat or delayed
gastric emptying
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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 aretouched simultaneously; indicates
dysfunction of the contralateral
posterior parietal lobe
drop metastases tumor masses inthe 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 &
spinal cord; consists of a thickfibrous tissue that is adherent to
the inner table of the skull &
forms a protective sheath in the
vertebral canal
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dural tail sign tailof dural enhancement seen on CT
or MRI in association with
meningeal neoplasms such
asmeningioma Duret
hemorrhages secondary
hemorrhages occurring in
the diencephalon, midbrain,
& ponsas downward movement ofthe 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
disorders of the vocal apparatus
(e.g., lips, tongue, larynx)
dysdiadochokinesia impairedability to perform rapid alternatingmovements (e.g.,
pronation/supination of hands);
indicates cerebellar dysfunction
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dysesthesia pain or discomfort inresponse to a stimulus (e.g., touch)
that would not be expected to
cause pain
dysgeusia distorted tasteperception
dysgraphia a writing disabilitythat results in incorrectly spelled
or written words dyskinesia blanket term for
movement disorders characterized
by increased motor activity
dyslexia disorder that limits theability to read
dysmetria difficulty judging &controlling the speed, distance, or
power of motor actions; tendency
to over- or underestimate the
extent of motion needed
dysphagia difficulty inswallowing
dysphonia voice disorder, oftenrelated to weakness of laryngeal
muscles, in which sound
production is impaired
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dysraphism defective closure ofa raphe, particularly the neural
tube
dyssomnia disorder in which themain complaint is about
inadequate or unrefreshing sleep
dystonia involuntary musclespasms that produce peculiar
postures of different body parts downward displacement of the
cerebral hemispheres pushing
the diencephalon & midbrainthr
ough the tentorial notch;
symptoms classically follow
a rostrocaudal deterioration
measurement of the eyes abilityto distinguish details; typically
expressed as a fraction in which
the numerator (20) indicates that
the subject is standing at 20 feetfrom a normal test object & the
denominator is the distance from
which a normal subject can read
the same normal image . entire
area visible to an eye that is
fixating straight ahead
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echolalia imitation of soundswithout comprehension of their
meaning
echopraxia imitative repetition ofthe movements, gestures, or
posture of another person
occasionally seen inTourette
syndrome
Edinger-Westphalnucleus accessory nucleus of eachoculomotor nerve that supplies
preganglionic parasympathetic
fibers for pupillary constriction &
lens accommodation; located in
the midline between the
extraocular oculomotor nerve
nuclei
efferent motor pathwayproceeding from the CNS toward
the peripheral end organs electromyography graphical
representation of the electrical
activity in a muscle
eidetic memory (photographicmemory) ability to vividly recall
visual images, sounds, or objects
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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 theplanning for epilepsy surgery &
resection of brain tumors &
vascular malformations in order to
minimize adverse outcomes from
surgery
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empty sella downwarddisplacement & compression of
the pituitary
gland by cerebrospinal fluid filling
thesella turcica; primary empty
sella syndrome occurs when asmall defect in the diaphragma
sellae increases pressure in the
sella & compresses the pituitary;
secondary empty sella syndrome
occurs when the sella is empty
because the pituitary has shrunkenfollowing injury, surgery, or
radiation
encephalitis inflammation ofbrain tissue
encephalocele failure of bonefusion in the posterior midline ofthe skull resulting in a bony cleft
through which meninges &/or
brain parenchyma protrude
encephalomalacia focal softening
of the brain in areas of tissue death
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following cerebral infarction,
infection, trauma, etc.
encephalopathy literally, "brainsuffering"; diffuse brain
dysfunction that may be caused by
toxins, infection, metabolic or
mitochondrial disease, tumor orincreased intracranial pressure,
trauma, or lack of blood flow or
oxygen to the brain; the hallmark
is impaired level of consciousness
endomysium innermost layer ofconnective tissue that forms aninterstitial layer around each
individual muscle fiber
endoneurium (epilemma)innermost layer of connective
tissue of a peripheral nerve thatforms an interstitial layer around
each individual axon / Schwann
cell unit
enophthalmos recession of theeyeball within the orbit
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eosinophilic neuronalnecrosis neuronal response
to ischemia & hypoxia characteriz
ed by brightly eosinophilic (red)
cytoplasm & nuclear shrinkage
ependyma epithelial lining of theventricles of the brain & the canal
of the spinal cord
ependymal cells typeof glia consisting of cuboidal cellslining the adult ventricles & spinal
canalependymal true rosette halo
of cells surrounding an empty
lumen; fairly specific for, though
infrequently seen
in, ependymomas
ependymoma WHO grade IIprimary CNS tumor of children
(involving the 4th ventricle) &
young adults (involving the spinalcord); characterized histologically
by perivascular pseudorosettes,
ependymal true rosettes, sharp
demarcation, & enhancement on
CT/MRI
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esotropia an eyewith strabismus that deviates
inward
essential tremor medium or highfrequency (4-9 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 systems electrical
response to the stimulation of
specific sensory pathways; see
also somatosensory evoked
potentials, brainstem auditory
evoked potentials, & visual
evoked potentials
excessive daytime sleepiness(hypersomnolence) subjective
difficulty in staying awake &easily falling asleep when
sedentary
excyclotorsion (a.k.a.extorsion): cyclotorsion of an eye
such that the superior pole rotates
outward
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executive functions higherintellectual functions such as
judgment, insight, reasoning,
abstraction
exophthalmos see proptosis exotropia an eye
with strabismus that deviates
outward
Expanded Disability StatusScale (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 plantarresponse extension of the greattoe (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
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suppression of more rostral motor
areas that have been damaged
extensor spasm manifestationof spasticity in which the legs
involuntarily straighten into an
extended position where they
remain for several minutes
extinction see doublesimultaneous stimulation
extra-axial within the skull orvertebral column but outside of the
brain or spinal cord
extrapyramidal movementdisorder not involving
the corticospinal tracts; typically
refers to basal
ganglia orcerebellar disorders
extrasylvian outside of the areasurrounding the Sylvian fissure;
often used synonymously with"transcortical," as in transcortical
motor aphasia & transcortical
sensory aphasia
measurement of the eyes abilityto distinguish details; typically
expressed as a fraction in which
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the numerator (20) indicates that
the subject is standing at 20 feet
from a normal test object & the
denominator is the distance from
which a normal subject can read
the same normal image . entire
area visible to an eye that is
fixating straight ahead
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F-wave long latency muscle actionpotential seen after supramaximal
stimulation to a nerve
facial masking(hypomimia) decreased facial
expression due to rigidity of facial
muscles
facial nerve (cranial nerveVII) predominantly motor nervesupplying muscles of facial
expression; also carries sensation
(external ear, taste from anterior
2/3 of tongue) via the nervus
intermedius &
preganglionicparasympathetic fibe
rs to the lacrimal, palatal, & nasal
glands
fainting falx cerebri fold of dura mater in
the sagittal sulcus between thetwo cerebral hemispheres
fascicle bundle of axons (nervefascicle) or muscle fibers (muscle
fascicle) surrounded by a layer of
contractile cells (perineurium for
nerves or perimusium for muscles)
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fasciculation spontaneous firingof an axon resulting in a visible
twitch of all the muscle fibers it
contacts; indicative of denervation
festination an involuntarytendency to take short accelerating
steps in walking that can occur
in Parkinson disease
fibrillation spontaneous firing of asingle muscle fiber not visible tothe 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 filum
terminale delicate fibrous tissue
structure surrounded by a few
nerve fibers that extends
downward from the conusmedullaris to the first segment of
the coccyx
finger agnosia typeof agnosia characterized by
inability to identify the fingers; a
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component of Gerstmann
syndrome
Fisher scale scale for grading CTappearance in patients with
nontraumatic subarachnoid
hemorrhage; higher scores
predictive of developing
symptomatic cerebral vasospasm
DescriptionGroup Nosubarachnoid blood detected 1Diffuse subarachnoid blood or
vertical layers of blood < 1 mm
thick 2 Localized clots &/or
vertical layers of blood < 1 mm
thick 3 Intracerebral orintraventricular clots with diffuse
or no subarachnoid blood 4
febrile seizure typicallybenign seizure associated with
high fever in children aged 3months to 5 years
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fibrinoid necrosis brightlyeosinophilic lesions in the small
vessels of the brain postulated to
occur because of disordered
cerebral autoregulation in
association with aging &
hypertension; contributes to thedevelopment of lacunar
infarction & hypertensive
hemorrhage
flaccidity severe form of
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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 flexorposturing stereotyped posture
occurring incoma in response to
stimulation in which the upper
extremity flexes & the lower
extremity extends; reflects release
of primitive responses from thesuppression of more rostral motor
areas that have been damaged & is
reminiscent of the decorticate state
demonstrated in animals with
transaction of corticospinal fibersabove the midbrain
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flexor response in thearm stereotyped posture occurring
in coma in response to stimulation
in which the upper extremity
flexes & the lower extremity
extends; reflects release of
primitive responses from thesuppression of more rostral motor
areas that have been damaged & 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 theposterior cerebellum; comprises
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the lateral portion of the
vestibulocerebellum
fluent aphasia (Wernickes orreceptive aphasia) impairment of
language comprehension including
impaired repetition due to lesion
of the posterior left superior
temporal gyrus (Brodmann
area 22) 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, &
the sagittal sutures come together),fuses at 7-19 months; the posterior
fontanel (where the lambdoid
& sagittal sutures come together)
is often fused at birth
foramen magnum large openingat the base of the skull throughwhich the spinal cord & vertebral
arteriespass from the vertebral
cavity into the cranial cavity
foramen of Magendie midline exitof CSF from the
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fourth ventricle into
the subarachnoid space
foramen of Monro permitscommunication of the
third ventricle with each of the
lateral ventricles on anterolateral
aspect of the third ventricle
foramina of Luschka lateral exitsof CSF from either side of thefourth ventricles into
the subarachnoid space
forebrain portion of the centralnervous system derived
from prosencephalon; commonly
used to denotecerebral
hemispheres & diencephalon
fornix white matter structurecontaining axons that connect
the hippocampus to
the hypothalamus & septalnuclei fortification spectrum
(teichopsia) complex
visual migraine aura consisting of
zig-zag lines or an arc of
scintillating lights forming into a
herringbone pattern & expanding
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to encompass an increasing
portion of a visual hemifield
Foster-Kennedysyndrome ipsilateral anosmia,
ipsilateral optic atrophy,
& contralateral papilledema due to
frontal lobe or olfactory groove
mass lesion
fovea center most part ofthe macula responsible for detailedcentral vision
Fovillesyndrome ipsilateral lateral gaze
palsy, ipsilateral peripheral facial
palsy,
& contralateral hemiplegiadue to
a dorsal pontine tegmentum lesion
affecting the paramedian pontine
reticular formation, facial
nervenucleus or fascicle,& corticospinal tract
fracture-dislocation fracturethrough the articular processes &
disc with or without associated
fracture through a vertebral body
due to flexion/extension with axial
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loading; unstable & often
associated with spinal cord injury
freezing sudden, brief cessation ofmovement; common in Parkinson
disease
Fresnel prisms clear, flexiblepolyvinyl chloride plastic sheets
composed of a series of small
prisms that are used to assess &correct diplopia
fried egg artifact perinuclear haloaround oligodendrocytes caused
by formalin fixation artifact
Friedreichs 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 byweakness, ataxia, sensory loss,
scoliosis, & cardiomyopathy
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frontal eye fields (FEF) regionwithin 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 towardsthe lesioned side (loss of
controversion), implying
unopposed stimulation from the
undamaged side
frontotemporal dementia groupof dementing illnesses in whichdisordered behavior (e.g.,
disinhibition) or language
(e.g., aphasia) are
disproportionately impaired in
relation to memory;includes Picks
disease &corticobasal
degeneration
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functional not due to organicdisease
measurement of the eyes abilityto distinguish details; typically
expressed as a fraction in whichthe numerator (20) indicates that
the subject is standing at 20 feet
from a normal test object & the
denominator is the distance from
which a normal subject can read
the same normal image . entirearea visible to an eye that is
fixating straight ahead
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gadolinium-enhancinglesion abnormality on MRI that
becomes bright after injection of
the chemical compound
gadolinium; implies breakdown in
the blood-brain barrier
gamma motorneurons neurons that contract the
ends of the muscle spindle so thatspindle sensitivity to passive
stretch is kept constant throughout
muscle shortening
ganglia aggregations of nerve cellbodies gegenhalten see paratonia
gemistocyte reactive astrocyte having increased glial filaments &
glassy eosinophilic cytoplasm
generalized seizure seizure thataffects both cerebral
hemispheres simultaneously &causes unconsciousness at the
outset
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geniculateganglion sensory ganglion of
the facial nerve that innervates
taste buds on the anterior 2/3 of
the tongue
genu kneelike bend in the anteriorpart of the corpus
callosum or internal capsule
germinal matrix a highlyvascular, metabolically active areaof the brain located just beneath
the ependymallining of the
ventricular walls, which is the
source of neurons & glial cells that
will later migrate to cerebral
cortex. It involutes in the second
trimester. Germinal matrix vessels
are fragile & are believed to have
impaired autoregulation, making
them prone to rupture in prematureinfants, resulting in
intraventricular hemorrhage.
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Gerstmann syndrome aneurological 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, & an inability to identify
fingers (finger agnosia) that is due
to a lesion of the angular gyrus of
the dominant parietal lobe
Glasgow Coma Scale (GCS) mostwidely used scoring system to
quantify level of consciousness
following traumatic brain injury;
scores range from 3 to 15, basedon the sum of the best eye opening
response, the best verbal response,
& the best motor response
Eye Opening(E)
Verbal Response(V)
MotorResponse
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glia supporting cells of thenervous system that provide
structural & metabolic support for
the neurons;includes astrocytes, oligodendrocy
tes, ependymal cells, & microglia
(M)
4=Spontaneous 5=Normal 6=Normal 3=To voice 4=Disoriented 5=Localizesto pain 2=To pain 3=Inappropriate 4=Withdrawto pain 1=None 2=Incomprehensible 3=Flexes topain 1=None 2=Extends topain 1=None
Total = E+V+M
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glioblastoma multiforme WHOgrade IV astrocytoma
characterized by hemorrhagic
necrosis, endothelial proliferation,
crossing of the corpus
callosum, ring-enhancement on
imaging, & poor survival
gliosis scar or dense fibrousnetwork of glial processes in anarea of CNS injury
global aphasia impairment oflanguage production,
comprehension, & repetition due
to lesion of entire perisylvian
region; usually associated with
right hemiparesis
globus pallidus most medialcomponent of the basal ganglia &
generator of most basal ganglionic
output
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glossopharyngeal nerve (cranialnerve IX) nerve containing motor,
sensory, & parasympathetic fibers;
motor fibers originate in
the nucleus ambiguus & innervate
the stylopharyngeus to elevate the
palate; sensory fibers originate in
the superior & petrosal ganglion &
supply taste to the posterior thirdof the tongue & tactile sensation to
the posterior tongue, pharynx,
middle & external ear, & eustacian
tube; parasympathetic fibers
originate in the inferior salivatory
nucleus & carry secretory &vasodilatory fibers to the parotid
gland
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gray matter part ofthe CNS consisting
of neuronal cell bodies
& dendrites
Guillain-Barre syndrome (acuteinflammatory demyelinating pol
yneuropathy) acute, ascending, &
progressive neuropathy believed to
result from an autoimmuneresponse triggered by an
antecedent illness or various
medical conditions &
characterized by
weakness, paresthesias,
hyporeflexia, &labile autonomicdysfunction; most
patients exhibit absent or
profoundly delayed conduction in
nerve fibers resulting
fromdemyelination, but in a subsetof patients, there is a direct
cellular immune attack on
the axon itselfgustatoryrelating to
the sense of taste
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gyrus convoluted ridge on theouter surface of the brain caused
by infolding of the cerebral
cortex & bound by sulci
measurement of the eyes abilityto distinguish details; typically
expressed as a fraction in which
the numerator (20) indicates thatthe subject is standing at 20 feet
from a normal test object & the
denominator is the distance from
which a normal subject can read
the same normal image . entire
area visible to an eye that isfixating straight ahead
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habenula diencephalic structurelocated on the dorsomedial surface
of the caudal thalamus that
receivesafferents from the
septal nuclei & hypothalamus via
the stria medullaris & projects
to midbrain nuclei; involved
in autonomic processing
hangmans fracture fracturethrough bilateral pedicles of C2via various mechanisms; typically
unstable
hemianesthesia loss ofsomatosensation on one half of the
body
hemianopia loss of vision in onehalf of the visual field, indicating a
pathological process posterior to
the optic chiasm
hemiballismus involuntary violentflinging or jerking of a limb (orlimbs) in an uncoordinated manner
caused by a lesion of
the contralateral subthalamus
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hemicraniacontinua indomethacin-responsive
headache disorder characterized
by steady, moderately intense
unilateral head pain on which are
superimposed episodes of more
intense pain
with autonomicsymptoms (eye
tearing, eye redness, eyelid edema,nasal congestion, runny nose)
occurring several times a day
hemifacialspasm segmental myoclonus of
muscles innervated by the facial
nerve; may be due to vascularcompression 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 sideof the body
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hemiplegic migraine familialform of migraine characterized by
temporary (usually < 1 hour but
occasionally lasting up to a
week) hemiparesis hemisensory
symptoms often associated with
visual aura & headache; in about
50% of affected families, a defect
may be found on chromosome 19or on chromosome 1 & involves
abnormal calcium channels
heterotopia tissue occurring in anabnormal anatomical
position hindbrain medulla, pons
& cerebellum
hippocampalformation cortical structure in the
medial temporal lobe comprising
the dentate gyrus,hippocampus,
& subiculum; involved in short-term declarative memory
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hippocampus convolutedstructure at the medial margin of
the cortical mantle of the cerebral
hemisphere, bordering the choroid
fissure of the lateral ventricle, &
forming part of the limbic system,
which is concerned with memory
& emotion
Hoffmans sign contraction offingers & thumb when a stimulusis applied to a distal phalanx in
that hand; indication of
hyperreflexia in the upper
extremity
holoprosencephaly failure ofcleavage at the rostral end of the
notochord resulting in midline
fusion of the frontal lobes, midline
facial abnormalities, &
often hydrocephalus & heterotopias Homer-Wright rosettehalo of
cells surrounding a central lumen
containing neuropil; found
in medulloblastomas & PNETs
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Horner'ssyndrome ptosis, miosis,
& anhidrosis ipsilateral to
damaged sympathetic nerve fibers
H-reflex electrical equivalent ofthe monosynaptic stretch reflex
elicited by selectively stimulating
the Ia fibers of the posterior tibial
or median nerve
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Hunt & Hess scale scale forgrading clinical status in patients
with nontraumatic subarachnoid
hemorrhagethat correlates well
with clinical outcome
Description Grade Asymptomatic,
mild headache,slight nuchal
rigidity 1 Moderate to
severe headache,
nuchal rigidity ,no neurologic
deficit other than
cranial nerve
palsy 2 Drowsiness /
confusion, mild
focal neurologic
deficit 3 Stupor, moderate-
severe
hemiparesis 4
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coma, decerebrateposturing 5
Huntington disease fatalautosomal dominant
neurodegenerative disorder
characterized by chorea &
progressive dementia; due to a
trinucleotide CAG-repeat mutation
on chromosome 4 hydranencephaly birth defect in
which the majority of the cerebral
hemispheres & striatum are absent
& replaced by sacs filled
with cerebrospinal fluid;
considered to be an extreme formof porencephaly
hydrocephalus literally "water onthe brain;" increase in size of
ventricles & amount
of cerebrospinal fluid in the brain
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hyperacusis abnormally increasedsensitivity to sound
hyperpathia exaggerated responseto painful stimuli
hypersomnolence see excessivedaytime sleepiness
hypertensivehemorrhage intraparenchymal
hemorrhage with a predilection to
occur deep in the cerebral
hemispheres, especially in
the putamen, thalamus, &
deep white matter, as well as
the pons & cerebellum. These sites
are all supplied by small
penetrating arteries that are subject
to high sheer stress & have no
collaterals, making themvulnerable to the effects of
increased blood pressure
hypertonicity increase in passivemuscle resistance, such
as spasticity or rigidity
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hypertropia an eyewith strabismus that deviates up
hypnagogic hallucination vividdreamlike hallucination that
occurs as one is falling asleep; oneof 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 AM
hypnic jerk sensation of falling, &then "jerking" awake just as onedrifts to sleep
hypnopompic hallucination vividdreamlike hallucination that
occurs as one is waking up; one of
the symptoms of narcolepsy, but
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also experienced by some non-
narcoleptic individuals
hypoglossal nerve (cranial nerveXII) motor nerve that innervates
all tongue muscles except thepalatoglossus; lesions result in
deviation of the protruded tongue
towards the paralyzed side &
deviation of the tongue at rest
away from the paralyzed
side; nucleus is located inthe medulla
hypomimia see facial masking hypophysis see pituitary gland hypothalamus basal part of
the diencephalon that controlshunger, thirst, body temperature,
& various metabolic processes,
including the maintaining of water
balance
hypotonicity reduction in passivemuscle resistance
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hypotropia an eyewith strabismus that deviates down
hypoxia reduction in the supply ofoxygen to the brain or other vital
organ
hypsarhythmia abnormal EEG pattern of excessive slow activity &multiple areas
of epileptiform activity; associated
with infantile spasms
measurement of the eyes abilityto 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 & the
denominator is the distance from
which a normal subject can readthe same normal image . entire
area visible to an eye that is
fixating straight ahead
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ice cream headache nicknamegiven to headaches that are cold
induced; common in migraine
ice-pick headache indomethacin-responsive headache disorder
characterized by momentary,
sharp, &/or jabbing pain that
occurs either once or several times
a day at irregular intervals ictus sudden attack, stroke,
or seizure
idiopathic occurring withoutknown cause; in the context
of epilepsy, indicates cases in
which no lesion is found & a
genetic cause is presumed
impairment problem in bodyfunction or structure such as a
significant deviation or loss (e.g.,
weakness = impairment in themuscles' capability to produce
force)
incisura fissure that separatesthe uncus from the apex of the
temporal lobe
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incyclotorsion (a.k.a.intorsion): cyclotorsion of an eye
such that the superior pole rotates
inward
indomethacin-responsiveheadache class of primary
headache disorders characterized
by a prompt & often complete
response to indomethacin to theexclusion of other nonsteroidal
anti-inflammatory drugs &
medications usually effective in
treating other primary headache
disorders; includes ice-pick
headache, chronic paroxysmalhemicrania, hemicrania
continua, cough headache,
& hypnic headache, among others
infantile spasms formof cryptogenic generalized epilepsy characterized by sudden,
forceful forward flexion of the
trunk & extension of the arms
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infarction permanent tissuedamage & 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 & from
the cerebellum;afferent fibers fromthe dorsal spinocerebellar
tract carry proprioceptive informat
ion from the upper
body;efferent fibers travel to the
vestibular nuclei in
the dorsal brainstem
inferior colliculus pairedstructures on the dorsal surface of
the caudal midbrain overlying
the cerebral aqueduct that process
& relay auditory signalsfrom brainstem centers to
the medial geniculate nucleus of
thethalamus; with the superior
collicui, make up the tectum &
the quadrigeminal bodies
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inferior olivarynucleus prominent nucleus in the
ventral medulla located just lateral
& dorsal to the
medullary pyramids; source of
climbing fibers that provide a
critical input to
the cerebellum involved in
Purkinje cell plasticity & motorlearning
infratentorial belowthe tentorium cerebelli,
i.e., brainstem & cerebellum
infundibulum connectionbetween the hypothalamus &
the pituitary gland (also called the
"pituitary