abducens nerve

8/3/2019 Abducens Nerve

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y abducens nerve (cranial nerve VI) motor nerve innervating the lateral rectus muscle, whichabducts the eye; lesions of the nucleus, which is located in the dorsalpons, produce a horizontal

gaze palsy; nerve fibers exit the ventromedial pons and because of their long course arevulnerable to damage by mass lesions/increased intracranial pressure

y abduct move away from the saggittal plane of the body

y absence seizure (petit mal seizure) generalized seizure characterized by abrupt cessation ofongoing activity with a blank stare and lost or impaired consciousness lasting on average 10-20seconds

y abulia loss of will, impulse, and decision-making ability

y acalculia "inability to calculate" or difficulty with arithmetic; may be the result of damage tothe angular gyrus in the hemisphere dominant for speech and language

y 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

y acrocephaly action potential seebrachycephaly

y 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

y action tremor tremorthat appears during movement of the affected body part

y 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

y activity limitations difficulties an individual may have in executing specific tasks or actions

(e.g., walking independently).

y acute developing over minutes to hours; implies acute metabolic dysfunction (e.g., ischemia,

seizure )

y Acute Disseminated Encephalomyelitis (ADEM) acute, classically monophasic

demyelinative disease of the CNS that may follow a viral syndrome or vaccination or noidentifiable predisposing cause

y adduct move towards the saggittal plane of the body

y Adies syndrome association ofAdies tonic pupil with absence ofmuscle stretch reflexes


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y Adies tonic pupil irregularly dilated pupil exhibiting minimal or no reaction to light, slowreaction to accommodation, and hypersensitivity to pilocarpine; typically idiopathic and most

often seen in young women

y adrenoleukodystrophy typically X-linked recessive demyelinative disease adrenal

dysfunction due to accumulation of very long chain fatty acids

y afferent sensory pathway proceeding toward the CNS from the peripheral receptor organs

y 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 damagedeye after first shining it in the normal eye

y ageusia impaired sense of taste

y 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 resultsfrom damage to the occipital or parietal lobe

y agraphia inability to communicate ideas in written language not due to mechanicaldysfunction; typically results from damage to the parietal lobe.

y akathisia motor restlessness; inability to sit still

y akinesiapaucity of movement akinetic mutism disorder of consciousness characterized byperiods of sleep and periods of wakefulness during which the patient lies with eyes open but isunresponsive, mute, and immobile; often due to frontal lobe damage

y alexia inability to read, usually due to a lesion of dominant occipitotemporal cortex

y alien hand syndrome syndrome characterized by the involuntary movement of a single upperlimb 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 anordinarily painless stimulus is experienced as being painful

y alpha motor neurons large motorneurons that innervate extrafusal skeletal muscle fibersalpha-synucleinprotein expressed predominantly in the CNS that when aggregated, can result in

neurodegenerative diseases such as Parkinson disease, dementia with Lewy bodies, andmultisystems atrophy

y Alzheimers disease most common cause ofdementia in older adults; a neurodegenerativedisease characterized by the gradual loss of cognitive ability in association with the

neuropathological findings of abnormal protein aggregates (neuritic plaques and neurofibrillarytangles) and neuron loss in the cerebral cortex


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y amaurosis fugax temporary loss of vision in one eye due to impairment of blood supplythrough the internal carotid artery or the ophthalmic artery

y amblyopia developmental abnormality in which a child fails to develop sharp visual acuity

y amygdala telencephalicgray matterstructure located in the anterior portion of the medialtemporal lobe involved in emotion, cognition and the regulation ofautonomic processes; part ofthe limbic system

y amyotrophic lateral sclerosis (Lou Gehrigs disease) inexorably progressive and fatal disease

of unknown cause characterized by slowly progressive degeneration ofupperand lowermotorneurons

y analgesia loss of pain sensation

y anencephaly (aprosencephaly) CNS malformation involving failure of closure of the

cephalic end of the neural tube, resulting in absence of the forebrain and cerebrum; rudimentarybrainstem may be present so that reflex actions such as breathing and responses to sound or

touch may occur

y aneurysm (brain aneurysm, cerebral aneurysm) a bulging formation on an artery, usually

caused by hypertension or an excessive amount of fatty deposits

y angular gyrus gyrus located immediately posterior to the supramarginal gyrus at the superioredge of the temporal lobe and involved in recognition of visual symbol; lesions can result inalexia and agraphia

y anhidrosis absence of sweating

y anisocoriapupillary asymmetry

y ankle-foot orthosis (AFO)brace that is worn on the lower leg and foot to support the ankle

and correct foot drop

y anomia inability to name objects or to recognize written or spoken names of objects

y anosmia loss of sense of smell

y anosognosia lack of awareness of or indifference to ones own neurological deficit, seen withnondominant parietal lobe lesions

y anterior cerebral artery a branch of the internal carotid artery; supplies blood to the medialaspect of the cerebral cortex (leg area predominant), some areas of the frontal lobe, corpuscallosum, caudate, and the anterior limb of the internal capsule


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y anterior commissure one of the three major groups of commissural fibers that coursesthrough thebasal ganglia and cross the midline in the anteriorforebrain to interconnect the

olfactory bulbs, amygdala, and hippocampal areas, among others

y anterior communicating arterybranch of the internal carotid artery that joins together the

paired anterior cerebral arteries

y anterior cord syndrome spinal cord injury syndrome associated with damage to the anterior2/3 of the spinal cord, often due to occlusion of the anterior spinal artery resulting in bilateralparalysis, bladder dysfunction, and loss of pain sensation below the level of the lesion

y anterior cranial fossaportion of the internal base of the skull housing the frontal lobes

y anterior horn (ventral horn)gray matterin the front of the spinal cord that containsmotor_neurons

y Anton's syndrome form ofcortical blindness in which the patient is unaware of/denies thevisual impairment; due to a lesion of the occipital lobe extending from primary visual cortex into

visual association cortex

y aphasia syndrome of disordered expression or comprehension of spoken and/or written

language caused by brain injury; see also non-fluent, fluent, conduction, global, transcorticalmotor, and transcortical sensory aphasia

y aphemia inability to speak words despite being able to make other sounds

y aphonia complete loss of voice

y apnea testpart 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)

y apraxia impaired planning/sequencing of movement that is not due to weakness,

incoordination, or sensory loss. Although the movements cannot be performed for a specificsituation, 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 legswhile lying in bed). Results from dissociation of parts of the cerebrum and is often associated

with parietal lobe lesions. aprosencephaly see anencephaly

y arachnoid middle layer of the meninges covering the brain and spinal cord

y arachnoid granulations (arachnoid villi) branched tufts ofarachnoid that project through thedura materinto the venous sinuses and function to return CSF to the systemic circulation


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y arachnoid villi diverticula of the arachnoid mater in the subarachnoid space that extend intothe veins and venous sinuses of the dura; a major pathway for the drainage ofcerebrospinal fluid

and transport across the endothelium into the blood.

y arcuate fasciculuspathway connecting Wernickes area in the posterior left superior temporal

gyrus to Brocas area in the left inferior frontal lobe; lesion results in impaired repetition

y area postrema chemoreceptor trigger zone for vomiting that is located on the dorsal surfaceof the medulla

y Argyll-Robertson pupilpupil exhibiting light-near dissociation due to a lesion in themidbrainperiaqueductal gray matter caused by tertiary syphilis arousal abrupt change fromsleep to wakefulness, or from a "deeper" stage ofnon-REM sleep to a "lighter" stage

y arteriovenous malformation a tangled collection of abnormal arteries and veins

y arteritis inflammation of an artery

y arthrokinetic nystagmus nystagmus induced by passive rotation of the arm of a stationarysubject seated in total darkness inside a rotating drum

y ascending tract of Deiters direct pathway (lying just lateral to the medial longitudinalfasciculus) from the vestibularnuclei to the ipsilateral medial rectus subnucleus; clinicalsignificance of this pathway is unclear

y aseptic meningitis syndrome characterized by headache, neck stiffness, low grade fever, andCerebro Spinal Fluid lymphocytic pleocytosis in the absence of an acute bacterial pathogen;

often used synonymously with viral meningitis, but also incudes meningeal inflammation due tovarious drugs (e.g., NSAIDs) or diagnostic procedures (e.g., angiography); atypical bacterial,

fungal, parasitic, orparameningeal infection; neoplastic processes; and various systemicdisorders

y asomatognosia inability to recognize part of ones own body, seen with nondominant parietallobe (or less commonly premotor cortex) lesions

y associated reactions movements of body parts other than the ones that are intended to move,

often increased with increased effort

y association cortex cortical areas involved in higher order processing of sensory information

and integration of multiple sensory and sensorimotor modalities astasia inability to standbecause of motor incoordination

y astasia-abasia functional stance and gait characterized by bizarre movements, typicallyswaying wildly and nearly falling, but then recovering at the last minute


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y asterixis sudden palmar flapping movement of the hands at the wrists; indicative of metabolicencephalopathy

y astrocytesCNSglia that function to orient neuroblast migration in the cerebral and cerebellarhemispheres, provide mechanical support, react to injury, insulate synaptic surfaces, provide a

source and sink for extracellular potassium, and uptake neurotransmitters to terminate theirsynaptic action astrocytoma most common central nervous system tumor derived from

astrocytesastrocytosis reaction ofastrocytes to neuronal injury characterized by an increase inthe number and size of astrocytes (primary reaction) and cytoplasmic changes including

increased glial filaments and glassy eosinophilic cytoplasm followed by formation of a densegliotic scar (secondary reaction)

y ataxia incoordination of movement usually due to disease ofcerebellaror sensory pathways

y athetosis involuntary, slow, writhing movements

y atonia loss of muscle tone

y atonic seizure (drop attack) generalized seizure characterized by sudden loss of muscle toneand 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

y aura

y automatism mechanical, seemingly aimless behavior (e.g., lip smacking or picking at clothes)characteristic ofcomplex partial seizures

y autonomicpertaining to the autonomic nervous system, which controls bodily functions thatare not under conscious control (e.g., heartbeat, breathing, sweating)

y autonomic nervous system part of theperipheral nervous system that regulates visceralfunction and homeostasis independent of voluntary control

y autoregulationphysiological process by which blood vessels change caliber to maintain

constant cerebral blood flow over a wide range ofcerebral perfusion pressuresaxial transverseplane producing a cross-section of the body or head

y axon long, slender projection from the neruonal cell body that is specialized for theconduction of information encoded in the form of action potentials

y axonal degeneration neuropathic process resulting in degeneration of the axon and its myelinsheath; preferentially involves the distal portion of the axon ("dying backneuropathy")

y axonal spheroid stereotypic axonal response to injury consisting of marked swelling due toaccumulation of materials undergoing axonal transport


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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 and

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

y Babinski response extension of the great toe on stimulation of the sole of the foot, signifying

a lesion of the corticospinal tract (a.k.a., upgoing toe); see alsoplantar response

y Balint syndrome syndrome comprisingparalysis of visual fixation, optic ataxia, andimpairment of visual fixation due to bilateral lesions of the parietal and occipital lobes

y basal ganglia large subcortical nuclear masses consisting of the caudate,putamen, globuspallidus, 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 stainingnuclei and little cytoplasm seen in the epithelium ofcraniopharyngiomas

y basilar artery largebrainstem artery located on the ventral surface of thepons formed by thejoining of the two vertebral arteries and bifurcating into theposterior cerebral arteries; supplies

blood to cerebral circulation and ventralpons

y basilar migraine form ofmigraine characterized by a visual aura followed by an oftenoccipital headache and one or more of the following symptoms: dysarthria, vertigo, tinnitus,decreased hearing, diplopia, blindness, ataxia, bilateralparesthesia, bilateralparesis, and

impaired cognition

y behavioral symptom complex changes in personality and behavior

y Bells 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

y Bell's phenomenon fluttering of the eyes upward when closed eyelids are opened by theexaminer

y Benedikt Syndrome ipsilateraloculomotorpalsy and contralateral hemichoreoathetosis due tolesion of the ventral midbraintegmentum affecting the IIII nerve fascicles and the red nucleus

y Berry aneurysm small saccular aneurysm of an intracranial artery

y Binswangers disease (subcortical leukoencephalopathy) degenerative white matterdiseaseproducing dementia due to hypertensive microvascular changes lipohyalinosis of the smallarteries and fibrinoid necrosis of the larger vessels inside the brain)

y blepharospasm excessive involuntary contraction of the orbicularis oculi sometimes resultingin functional blindness; a focal dystonia


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y blood-brain barrier specialized system of capillary endothelial cells that strictly limitstransport into the brain through both physical (tight junctions) and metabolic (enzymes) barriers

y borderzone infarct see watershed infarct

y brachial relating to the arm

y brachium anatomical structure comprising a collection ofaxons that resemble an arm

y brachium conjunctivum see superior cerebellar peduncle

y brachium pontis see middle cerebellar peduncle

y brachycephaly (acrocephaly)premature fusion of bilateral coronal sutures producing aforeshortened skull

y bradykinesia slowed movement due to dysfunction of thebasal ganglia and related structures

y bradyphrenia slowing of thought processes that can occur in Parkinson disease or as a sideeffect of antipsychotic medications

y brain death see death by neurological criteria

y brainstem medulla,pons, and midbrain

y brainstem auditory evoked potentials (BAEP) series of waves that reflect sequentialactivation 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 thevertex 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), universalnewborn hearing screening, and intraoperative monitoring

y brain death

y Brocas aphasia see non-fluent aphasia

y Brodmann's areas distinct regions of the cerebral cortex recognized by variations in cell size,

density, and thickness of the cortical layers

y 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 vibrationproprioception and contralateral loss of pain sensation

y Brudzinskis sign involuntary flexion of the hips in response to passive flexion of the neck;indicative ofmeningeal irritation


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y bruxism grinding one's teeth while asleep

y bulbarpertaining to the lower cranial nerve nuclei

y 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





y calcarine cortexprimary visual cortex located in the occipital lobe (striate area 17)

y 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 andtransmural pressure

y carphologia see floccillation

y catamenial referring to menses; with regard to women with epilepsy ormigraine, a tendencyforseizures/migraines to occur around the time of menses

y cataplexy sudden loss of postural tone, often triggered by an emotional stimulus and resultingin falls to the floor; seen in narcolepsycauda equina (horses 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 theperipheral nervous system, lesions produce lower motor neuron deficits

y caudal toward the tail

y caudateportion of thebasal ganglia that lies in the floor of the lateral ventricle

y cavernoma (cavernous malformation) vascular malformations composed primarily of largevenous channels without a clear-cut arterial component

y cavernous sinuspaired, venous structures located on either side of the sella turcica thatreceive 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, andproptosis

y central chromatolysis regenerative response to axonal injury consisting ofneuronal swelling,nuclear eccentricity, and loss of Nissl substance


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y central cord syndrome spinal cord injury syndrome associated with damage to the centralportion 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

y central herniation downward displacement of the cerebral hemispheres pushing the

diencephalon and midbrain through the tentorial notch; symptoms classically follow arostrocaudal deterioration

y central nervous system (CNS)brain and spinal cord

y central pain syndrome intense pain arising from injury to the central nervous system, mostoften in patients who have had a stroke, multiple sclerosis, or brain injury.

y central sulcusprominent sulcus on the dorsolateral aspect of the cerebral hemispheres formedby the precentral and postcentral gyri; defines the boundary between the frontal and parietal

lobes

y centrum semiovale expansive region ofwhite matterin the dorsal core of the frontal and

parietal lobes, named because of its central position in the forebrain and its semi-oval shape

y cephalic relating to the head

y cerebellar peduncle three majorwhite matterstructures containing #efferent and afferentaxons of the cerebellum; named the inferior, middle, and superiorcerebellarpeduncles

y cerebellar tonsil lateral portions of the uvula located in the posterior lobe of the cerebellum

y cerebellopontine angle space located at the junction of the cerebellum,pons, and medullacontaining cranial nerves V-XI, blood vessels, the flocculus of the cerebellum, and choroid

plexus

y cerebellumbrain structure inposterior fossa that coordinates the many muscles active in any

given movement; receives input from spinal cord and cerebral cortex and projects to postural andvoluntary motor control systems and red nucleus

y cerebral amyloid angiopathy (congophilic angiopathy) vascular disorder in which betaamyloid 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 causeof predominantly lobar intracerebral hemorrhage in the elderly

y cerebral aqueductportion of the ventricular system that lies in the dorsal midbrain andconnects the third and fourth ventricles

y cerebral arteriosclerosis thickening and hardening of the arteries within the brain


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y cerebral atherosclerosisbuild-up of fatty deposits in the inner wall of cerebral arteries; formofcerebral arteriosclerosis

y cerebral atrophy the shrinking of the brain or brain cells.

y cerebral autosomal dominant arteriopathy with subcorticalinfarcts &leukoencephalopathy (CADASIL) familial arterial disease of the brain caused by mutations inthe Notch3 gene and consisting of recurrent subcorticalstrokes starting in midadult life,

dementia, depression, and migraine

y cerebral cortex highly convoluted layer ofgray matterthat constitutes the outermost layer ofthe cerebrum and is responsible for integrating sensory impulses and for higher intellectualfunctions

y cerebral hemisphere symmetrical half of the cerebrum as separated by the sagittal sulcus and

containing the cerebral cortex,basal ganglia, hippocampus, and amygdala

y cerebral peduncle (crus cerebri) white mattertracts (corticospinal and corticobulbar) on the

ventral surface of the midbrain containing the efferentaxons ofcerebral cortex that project tobrainstem and spinal cord

y cerebral perfusion pressure (CPP) mean arterial pressure (MAP) intracranial pressure(ICP)

y cerebral salt wasting centrally-mediated hypovolemic hyponatremia associated with negativesodium 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 ofsympathetic input to the kidneys, production of a circulating natriuretic factor, or both

y cerebritis inflammation of the brain

y cerebrospinal fluid (CSF) clear, colorless fluid bathing the entire surface of the CNS, most ofwhich 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 andthe 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 ofdural sinuses and returned to the systemiccirculation

y cerebrum anteriorportion of the brain consisting of the two cerebral hemispheres that each

contain four lobes

y Charcot-Bouchard aneurysm aneurysmal dilation of small intraparenchymal vessels

commonly seen in the brains of patients with hypertensive hemorrhage


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y Charcot jointprogressive destruction and deformity of bone and soft tissue at weight bearingjoints due to severe sensory or autonomic neuropathy cheiro relating to the hand

y Chiari malformation CNS disorder characterized by cerebellarelongation and protrusionthrough the foramen magnum into the cervical spinal cord. Type I consists ofcaudal

displacement of the medulla and inferior pole of the cerebellarhemispheres through the foramenmagnum. 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 bifidacystica. Type IV involves cerebellarhypoplasia

y chorea involuntary, irregular, rapid, jerking movements

y choroid plexus intraventricular structure that secretes cerebrospinal fluid

y 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 ofCSF; may also be seen in thecerebellopontine angle

y chronic daily headache headache disorder consisting of frequent headache occurring 15 or

more days per month and including headache associated with medication overuse

y chronic paroxysmal hemicrania indomethacin-responsive headache disorder characterized

by the occurrence of multiple daily attacks lasting 5 to 30 minutes of severe unilateral head painoften associated with autonomic phenomenon (eye tearing, eye redness, eyelid edema, nasal

congestion, runny nose); also known as atypical cluster headache

y chronic-progressive developing over months to years; implies gradual deterioration as occurswith degenerative diseases like Alzheimer disease, Huntington disease, etc.

y cingulate gyrus cortical component of the limbic system located on the medial aspect of thehemisphere superior to the corpus callosum; involved in emotional and cognitive processing

y cingulate herniation horizontal displacement of a cerebral hemisphere due to an expandinglesion that forces the cingulate gyrus under the falx cerebri, compressing the internal cerebralvein and the contralateral hemisphere

y circadian rhythm innate daily fluctuation of physiological or behavioral functions, including

sleep-wake states generally tied to the 24-hour daily dark-light cycle

y Circle of Willis the main arterial anastomatic trunk located at the base of the brain; place

where the two internal carotid arteries and thebasilarartery come together, allowing blood to beredistributed to the anterior, middle, andposteriorcerebral arteries

y classic migraine see migraine with aura


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y Claude Syndrome ipsilateraloculomotorpalsy and contralateralataxia andhemichoreoathetosis due to a dorsal midbraintegmental lesion affecting the III nerve fascicles,

superior cerebellar peduncle, and red nucleus

y claustrum thin plate ofgray matterlying in the white matterbetween the insula and thebasal

ganglia that modulates cortical activity

y clay shovelers fracture typically stable fracture through a spinous process due tohyperextension injury

y clonic seizure generalized seizure characterized by jerking movements on both sides of thebody

y clonus rhythmic contraction relaxation tremordue to cyclic alternations of the spindle stretchreflex and the Golgi tendon organ reflex; indicative of exaggerated stretch reflexes

y cluster headacheprimary 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" formonths or years; diagnosis requires one or more of the following autonomic abnormalities

ipsilateral to the headache: conjunctival injection, lacrimation,ptosis, miosis, eyelid edema, nasalcongestion, rhinorrhea, or facial sweating CNS central nervous system

y CNS metastasis metastatic tumors typically spread by a hematogenous route and found at thejunction between gray matterand white matterwhere they are trapped by the acute angle

branching of the microvasculature

y cogwheeling ratchety movement due to superimposition oftremoron rigidity

y coital headache indomethacin-responsive headache disorder characterized by sudden, severe,throbbing, occipital headache that occurs just before or during orgasm

y cold calorics see oculovestibular response

y coma state of unarousable unresponsiveness with closed eyes, no speech, and no purposefulmovements

y common carotid artery artery that arises from the brachiocephalic artery on the right andfrom 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

y common migraine see migraine without auracommunicating hydrocephalus blockage of

CSF flow outside the ventricular system, either at the level of the arachnoid granulations orbecause of overproduction of CSF (e.g., from a choroid plexus papilloma) that exceeds the rate

of absorption


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y complex partial seizurepartial seizure 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

y complex tic distinct, coordinated patterns of successive movements involving several muscle

groups; complex vocal tics include meaningful syllables, words, or phrases; complex motor ticsare coordinated or sequential patterns of movement such as twirling a pencil or touching other

people

y concussion traumatic closed head injury that results in temporary impairment of neurologicalfunction, e.g., transient loss of consciousness

y conduction aphasia selective impairment of the ability to repeat due to a lesion of the arcuatefasciculus, which connects Wernickes area to Brocas area

y conduction blockfailure of impulse conduction along an anatomically intact axon;

characteristic ofdemyelinatingneuropathy

y contracoup opposite to the site of impact

y contracturepermanent 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

y contralateral located on the opposite side of the body (brain)

y contusion edematous brain lesion containing punctuateparenchymal hemorrhages on thesurface of the brain that may extend bidirectionally into the white matterand the subdural and

subarachnoid spaces; occur at the site of impact (coup contusion) with direct trauma and at a siteopposite to the site of impact (contracoup contusion) with acceleration/deceleration injury

y conus medullariscaudal-most part of the spinal cord located between the first and secondlumbar 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

y convergence coordinated inward movement of the eyes in order to fixate on a near objectconvergence-retraction nystagmus form ofnystagmus consisting of jerking eye movements

inward and backward; associated with dorsal midbrain lesion

y coprolalia uncontrolled, often obsessive use of obscene language occasionally seen in

Tourette syndrome

y 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 towardthe thalamus where they will form the internal capsule


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y corpus callosum large fiber structure 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.

y corpus striatum see striatum

y cortical referring to the cerebral cortex, the outermost layer of the cerebrum

y cortical blindness apparent lack of visual functioning in spite of anatomically and structurallyintact eyes due to bilateral lesions of the primary visual cortex

y corticobasal degenerationprogressive neurological disorder characterized by nerve cell lossin the cerebral cortex andbasal ganglia and producingparkinsonism, dementia, visual-spatial

impairment, alien hand syndrome, apraxia, and myoclonus

y corticobulbar tract axons originating in the posterior frontal lobe and projecting to lower

motor neurons in thebrainstem

y corticospinal tract (pyramidal tract) motor pathway responsible for voluntary movementthat arises from primary motorcortex, area 6, and somatosensory cortex and descends throughthe corona radiata, internal capsule, cerebral peduncle, medullarypyramid (where it decussates),

and spinal cord to alpha motor neurons in spinal cord gray matter

y cough headache indomethacin-responsive headache disorder characterized by transient,severe, explosive head pain upon coughing, sneezing, weight lifting, bending, or stooping

y 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 encephalitisCowdry B inclusion bodies large glassy eosinophilic nuclear inclusions occurring in herpes

simplex encephalitis

y craft palsy dystonia occurring in the setting of a highly learned skilled task, e.g., writerscramp, yips in golfers

y craniectomy surgical removal of a section of bone (bone flap) from the skull for the purposeof operating on the underlying tissues or relieving intracranial pressure, in which the bone flap is

not replaced at the end of the procedure

y craniopharyngioma suprasellarWHO 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 fatalneural tube defect consisting of total failure ofneurulation; a neural plate-like structure is

entirely exposed without overlying bony or dermal covering


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y craniosynostosispremature closure at birth of one or more cranial sutures, which limits headgrowth perpendicular to the suture(s); see alsobrachycephaly, oxycephaly,plagiocephaly,

scaphocephaly, trigonocephaly

y 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 procedurecreatine kinase enzyme that catalyzes the conversion of creatine to phosphocreatine and is

released into the blood by tissuesparticularly musclethat consume adenosine triphosphate(ATP) rapidly; elevated levels are seen in myopathy

y cremasteric reflex superficial (cutaneous) reflex elicited by stroking the superior and medialpart 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 andL2

y Creutzfeldt-Jakob disease fatalprion disease characterized by spongiform changes in the

brain, progressive dementia, psychiatric changes, and myoclonus; form ofspongiformencephalopathy

y crossed adductor reflex reflex contraction of the adductor magnus caused by tapping theopposite 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

y crural relating to the leg crus cerebri see cerebral peduncle

y cryptogenic occurring without known cause; in the context ofepilepsy, indicates cases in

which a lesion and distinct pathogenesis are presumed

y cyclotorsion (a.k.a. torsion): rotation of the eye around an anterior-posterior axis; seeexcyclotorsion, incyclotorsion

corticobasal degeneration 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 and 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

y

Dawsons fingers ovoid demyelinating lesions with their long axis perpendicular to theventricular surface seen in multiple sclerosis

y death by neurological criteria irreversible loss of all brain function

y decerebrate rigidity stereotyped posture consisting of extension of all four limbs occurringwith transaction between the superior collicui and inferior colliculi in the midbrain; often used

synonymously with extensor posturing


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y decorticate rigidity stereotyped posture consisting of flexion of the forelimbs and extensionof the hindlimbs occurring with transaction between the diencephalon and midbrain; often used

synonymously with flexor posturing

y decussate to cross

y deja vu feeling as if one has lived through or experienced this moment before; may occur inpeople without any medical problems or as a seizureaura_

y 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 conventionalbedtime; common in young adults

y 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

y dementia acquired and sustained loss of memory and other intellectual functions that is of

sufficient severity to interfere with daily functioning dementia pugilistica chronic traumaticencephalopathy caused by cumulative and repetitive head trauma and manifesting as dementia

andparkinsonism

y demyelination destruction or loss of the myelin sheath surrounding axons; results in impaired

nerve impulse conduction

y dendrite receiving portion of the neuron

y denervation loss of nerve supply

y dermatome distribution of sensory innervation on the skin of the body and the limbs

y diabetes insipidus inability to concentrate urine resulting from decreased secretion of

antidiuretic hormone; reflects a lesion of the hypothalamic osmoreceptors, supraoptic orparaventricularnuclei, or the supraopticohypophyseal tract and may occur in transtentorial

herniation due to downward traction on the hypothalamic median eminence

y diaphragma sellae thin dural membrane overlying the sella turcica that is fenestrated to allow

passage of the infundibulum

y diaschisis depression of metabolism at sites distant from, but connected with, a site of cerebral

injury (e.g., infarction) due to interruption ofafferent orefferent fiber pathways

y diastematomyelia longitudinal division of the spinal cord by a septum of bone

y diencephalon thalamus, hypothalamus, subthalamic nucleus, andpineal


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y diffuse axonal injury widespread damage to white matterdue to rotational shearing forceswith head trauma

y diffuse Lewy body disease (Lewy body dementia) form ofdementia associated withfluctuating alertness, recurrent visual hallucinations, andparkinsonism and defined

pathologically by cortical (as well as nigral) Lewy bodies

y diplegia seeparaplegia

y diplopia double vision

y dissociated sensory deficit impairment of pain/temperature sensation with preservation ofvibration/proprioception or vice versa; implies lesion ofbrainstem or spinal cord involving 1

sensory tract but sparing the other

y dolichocephaly see scaphocephaly

y dolls phenomenon see oculocephalic response

y dorsalposterior

y dorsal columns ascending axonal tract running in the dorsal funiculus of the spinal cord thatcarries tactile andproprioceptive information to the brain; fibers cross in the ventromedial

medulla to become the medial lemniscusdorsal horn see posterior horn

y dorsal motor nucleus of the vagusparasympathetic nucleus that stimulates secretion fromglands of the pharynx and thoracic and abdominal viscera

y dorsal rhizotomy surgical procedure involving sectioning of the dorsal spinal nerve rootsperformed to reduce spasticity

y dorsal root ganglion collection of cell bodies located in the intervertebral foramina thattransduce sensory information into neural signals and transmit these signals to the CNS

y dose failurephenomenon in which an individual dose of medication has no effect; occurs inParkinson disease possibly in association with a tablet getting stuck in the throat or delayed

gastric emptying

y double simultaneous stimulation (DSS) ability to detect two stimuli applied simultaneouslyto opposite sides of the body; for tactile DSS, if a patient is able to identify which side is beingtouched 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 posteriorparietal lobe


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y drop metastases tumor masses in the lumbosacral spinal cord due to CSF spread of neoplasticcells (e.g., medulloblastoma)

y duction movement of one eye

y dura mater outermost layer of the meninges covering the brain and spinal cord; consists of athick fibrous tissue that is adherent to the inner table of the skull and forms a protective sheath inthe vertebral canal

y dural tail sign tail ofdural enhancement seen on CT or MRI in association with meningeal

neoplasms such as meningiomaDuret hemorrhages secondary hemorrhages occurring in thediencephalon, midbrain, and pons as downward movement of thebrainstem relative to theimmobile blood vessels on the surface of the brainstem results in injury to small penetrating

blood vessels; sequelae of cerebral herniation

y dysarthria inability to pronounce or articulate words due to disorders of the vocal apparatus

(e.g., lips, tongue, larynx)

y dysdiadochokinesia impaired ability to perform rapid alternating movements (e.g.,pronation/supination of hands); indicates cerebellardysfunction

y dysesthesiapain or discomfort in response to a stimulus (e.g., touch) that would not beexpected to cause pain

y dysgeusia distorted taste perception

y dysgraphia a writing disability that results in incorrectly spelled or written words

y dyskinesiablanket term for movement disorders characterized by increased motor activity

y dyslexia disorder that limits the ability to read

y dysmetria difficulty judging and controlling the speed, distance, or power of motor actions;

tendency to over- or underestimate the extent of motion needed

y dysphagia difficulty in swallowing

y

dysphonia voice disorder, often related to weakness of laryngeal muscles, in which soundproduction is impaired

y dysraphism defective closure of a raphe, particularly the neural tube

y dyssomnia disorder in which the main complaint is about inadequate or unrefreshing sleep

y dystonia involuntary muscle spasms that produce peculiar postures of different body parts


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y downward displacement of the cerebral hemispheres pushing the diencephalon andmidbrain through the tentorial notch; symptoms classically follow a rostrocaudal

deterioration


the numerator (20) indicates that the subject is standing at 20 feet from a normal test object andthe denominator is the distance from which a normal subject can read the same normal image .


y echolalia imitation of sounds without comprehension of their meaning

y echopraxia imitative repetition of the movements, gestures, or posture of another personoccasionally seen in Tourette syndrome

y Edinger-Westphal nucleus accessory nucleus of each oculomotor nerve that suppliespreganglionic parasympathetic fibers for pupillary constriction and lens accommodation; located

in the midline between the extraocular oculomotor nerve nuclei

y efferent motor pathway proceeding from the CNS toward the peripheral end organs

y electromyography graphical representation of the electrical activity in a muscle

y eidetic memory (photographic memory) ability to vividly recall visual images, sounds, orobjects in memory with extraordinary detail

y electroencephalogram (EEG) system for recording the electrical potentials of the brain

derived from electrodes attached to the scalp eloquent cortex regions of the cerebral cortexresponsible for motor, sensory, language or other cognitive processing that if removed, willresult 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 vascularmalformations in order to minimize adverse outcomes from surgery

y empty sella downward displacement and compression of thepituitary gland by cerebrospinalfluid filling the sella turcica; primary empty sella syndrome occurs when a small defect in the

diaphragma sellae increases pressure in the sella and compresses thepituitary; secondary emptysella syndrome occurs when the sella is empty because thepituitary has shrunken following

injury, surgery, or radiation

y encephalitis inflammation of brain tissue

y encephalocele failure of bone fusion in the posterior midline of the skull resulting in a bonycleft through which meninges and/or brainparenchyma protrude encephalomalacia focal

softening of the brain in areas of tissue death following cerebral infarction, infection, trauma, etc.


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y encephalopathy literally, "brain suffering"; diffuse brain dysfunction that may be caused bytoxins, 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 ofconsciousness

y endomysium innermost layer of connective tissue that forms an interstitial layer around eachindividual 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

y enophthalmos recession of the eyeball within the orbit

y eosinophilic neuronal necrosisneuronal response to ischemia and hypoxia characterized bybrightly eosinophilic (red) cytoplasm and nuclear shrinkage

y ependyma epithelial lining of the ventricles of the brain and the canal of the spinal cord

y ependymal cells type ofglia consisting of cuboidal cells lining the adult ventricles and spinalcanal ependymal true rosette halo of cells surrounding an empty lumen; fairly specific for,though infrequently seen in, ependymomas

y ependymomaWHO grade II primary CNS tumor of children (involving the 4th ventricle) and

young adults (involving the spinal cord); characterized histologically by perivascularpseudorosettes, ependymal true rosettes, sharp demarcation, and enhancement on CT/MRI

y ephaptic electrical conduction of a nerve impulse across a non-synaptic contact site between

nerves and without the mediation of a neurotransmitter

y epilepsy chronic brain disorder of various etiologies characterized by recurrent unprovokedseizures

y 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

y epithalamus dorsal posterior subdivision of the diencephalon generally considered to includethe habenula, thepineal body, and the epithelial roof of the third ventricle

y esotropia an eye with strabismus that deviates inward

y essential tremor medium or high frequency (4-9 Hz) tremorthat occurs with action or

holding a sustained posture that typically affects the arms, the head/neck, or the voice


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y evoked potentials recordings of the nervous systems electrical response to the stimulation ofspecific sensory pathways; see also somatosensory evoked potentials,brainstem auditory evoked

potentials, and visual evoked potentials

y excessive daytime sleepiness (hypersomnolence) subjective difficulty in staying awake and

easily falling asleep when sedentary

y excyclotorsion (a.k.a. extorsion): cyclotorsion of an eye such that the superior pole rotatesoutward

y executive functions higher intellectual functions such as judgment, insight, reasoning,abstraction

y exophthalmos seeproptosis

y exotropia an eye with strabismus that deviates outward

y Expanded Disability Status Scale (EDSS) 20-point scale, ranging from 0 (normalexamination) to 10 (death) by half-points, that measures impairment (gait is heavily

emphasized); used in clinical trials ofmultiple sclerosis

y extensor plantar response extension of the great toe (upgoing toe) with fanning of theother toes in response to application of a stimulus to the skin of the foot or leg; signifies a lesionof the corticospinal tract

y extensor posturing

y extensor response in the arm stereotyped posture occurring in coma in response tostimulation in which the upper extremity extends (shoulder extends, adducts, and internally

rotates; elbow extends; forearm hyperpronates; wrist and fingers flex); may be accompanied byextension of the lower extremity (hip extends, adducts, and internally rotates; knee extends; footplantar flexes and inverts) as in decerebrate rigidity; reflects "release" of primitive responses

from the suppression of more rostral motor areas that have been damaged

y extensor spasm manifestation ofspasticity in which the legs involuntarily straighten into anextended position where they remain for several minutes

y extinction see double simultaneous stimulation

y extra-axial within the skull or vertebral column but outside of the brain or spinal cord

y extrapyramidal movement disorder not involving the corticospinal tracts; typically refers tobasal ganglia orcerebellardisorders


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y extrasylvian outside of the area surrounding the Sylvian fissure; often used synonymouslywith "transcortical," as in transcortical motor aphasia and transcortical sensory aphasia



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

y F-wave long latency muscle action potential seen after supramaximal stimulation to a nerve

y facial masking (hypomimia) decreased facial expression due to rigidity of facial muscles

y facial nerve (cranial nerve VII)predominantly motor nerve supplying muscles of facialexpression; also carries sensation (external ear, taste from anterior 2/3 of tongue) via the nervus

intermedius and preganglionicparasympathetic fibers to the lacrimal, palatal, and nasal glands

y fainting

y falx cerebri fold ofdura mater in the sagittal sulcus between the two cerebral hemispheres

y fascicle bundle ofaxons (nerve fascicle) or muscle fibers (muscle fascicle) surrounded by alayer of contractile cells (perineurium for nerves orperimusium for muscles)

y fasciculation spontaneous firing of an axon resulting in a visible twitch of all the musclefibers it contacts; indicative of denervation

y festination an involuntary tendency to take short accelerating steps in walking that can occurin Parkinson disease

y fibrillation spontaneous firing of a single muscle fiber not visible to the naked eye, indicativeof denervation or irritable myopathy; seen electrographically as a brief action potential with

initial positive (down) wave followed by negative (up) wave filum terminale delicate fibroustissue structure surrounded by a few nerve fibers that extends downward from the conus

medullaris to the first segment of the coccyx

y finger agnosia type ofagnosia characterized by inability to identify the fingers; a componentofGerstmann syndrome

y Fisher scale scale for grading CT appearance in patients with nontraumatic subarachnoidhemorrhage; higher scores predictive of developing symptomatic cerebral vasospasm

DescriptionGroup No subarachnoid blood detected 1 Diffuse subarachnoid blood or verticallayers of blood < 1 mm thick 2 Localized clots and/or vertical layers of blood < 1 mm thick 3

Intracerebral or intraventricular clots with diffuse or no subarachnoid blood 4


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y febrile seizure typically benign seizure associated with high fever in children aged 3 monthsto 5 years

y fibrinoid necrosis brightly eosinophilic lesions in the small vessels of the brain postulated tooccur because of disordered cerebral autoregulation in association with aging and hypertension;

contributes to the development oflacunar infarction and hypertensive hemorrhage

y flaccidity severe form ofhypotonicity

y 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 posturingstereotyped posture occurring in coma in response to stimulation in which the upper extremityflexes 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 thedecorticate state demonstrated in animals with transaction of corticospinal fibers above the

midbrain

y flexor response in the arm stereotyped posture occurring in coma in response to stimulationin 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 isreminiscent of the decorticate state demonstrated in animals with transaction of corticospinal

fibers above the midbrain

y flexor spasm often painful manifestation ofspasticity in which the legs involuntarily pull

upward into a clenched position for a period of a few seconds

y floccillationpurposeless picking at clothing or bedding seen in delirium

y flocculus small lobe of the posteriorcerebellum; comprises the lateral portion of thevestibulocerebellum

y fluent aphasia (Wernickes or receptive aphasia) impairment of language comprehensionincluding impaired repetition due to lesion of the posterior left superior temporal gyrus

(Brodmann area 22)

y fontanel soft membranous gap between the incompletely formed cranial bones of a fetus or aninfant; the anterior fontanel (where the metopic, the two coronal, and the sagittal sutures cometogether), 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 skullthrough which the spinal cord and vertebral arteries pass from the vertebral cavity into the

cranial cavity

foramen of Magendie midline exit ofCSF from the fourth ventricle into the subarachnoid space

y foramen of Monropermits communication of the third ventricle with each of the lateralventricles on anterolateral aspect of the third ventricle


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foramina of Luschka lateral exits ofCSF from either side of the fourth ventricles into thesubarachnoid space

y forebrainportion of the central nervous system derived fromprosencephalon; commonly used

to denote cerebral hemispheres and diencephalon

y fornix white matterstructure containing axons that connect the hippocampus to the

hypothalamus and septal nuclei

y 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 encompassan increasing portion of a visual hemifield

y Foster-Kennedy syndrome ipsilateralanosmia, ipsilateral optic atrophy, and contralateralpapilledema due to frontal lobe or olfactory groove mass lesion

y fovea center most part of the macula responsible for detailed central vision

y Foville syndrome ipsilateral lateral gaze palsy, ipsilateral peripheral facial palsy, andcontralateralhemiplegia due to a dorsal pontine tegmentum lesion affecting theparamedianpontine reticular formation, facial nervenucleus orfascicle, and corticospinal tract

y 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; unstableand often associated with spinal cord injury

y freezing sudden, brief cessation of movement; common in Parkinson disease

y Fresnel prisms clear, flexible polyvinyl chloride plastic sheets composed of a series of small

prisms that are used to assess and correct diplopia

y fried egg artifact perinuclear halo around oligodendrocytes caused by formalin fixationartifact Friedreichs ataxia autosomal recessive neurodegenerative disease caused by GAA tripletrepeat mutation in the gene that encodes for frataxin, a protein that regulates mitochondrial

functioning; characterized by weakness, ataxia, sensory loss, scoliosis, and cardiomyopathy

y frontal eye fields (FEF) region within the frontal lobes from which voluntary lateral eyemovements 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 ofcontroversion), implying unopposed stimulation from the undamaged side

y frontotemporal dementia group ofdementing illnesses in which disordered behavior (e.g.,disinhibition) or language (e.g., aphasia) are disproportionately impaired in relation to memory;includes Picks disease and corticobasal degeneration


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y functional not due to organic disease





y gadolinium-enhancing lesion abnormality on MRI that becomes bright after injection of the

chemical compound gadolinium; implies breakdown in theblood-brain barrier

y 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

y ganglia aggregations of nerve cell bodies gegenhalten seeparatonia

y

gemistocyte reactive astrocyte having increased glial filaments and glassy eosinophiliccytoplasm

y generalized seizure seizure that affects both cerebral hemispheres simultaneously and causesunconsciousness at the outset

y geniculate ganglion sensory ganglion of the facial nerve that innervates taste buds on the

anterior 2/3 of the tongue

y genu kneelike bend in the anterior part of the corpus callosum orinternal capsule

y germinal matrix a highly vascular, metabolically active area of the brain located just beneaththe ependymal lining of the ventricular walls, which is the source ofneurons and glial cells that

will later migrate to cerebral cortex. It involutes in the second trimester. Germinal matrix vesselsare fragile and are believed to have impaired autoregulation, making them prone to rupture in

premature infants, resulting in intraventricular hemorrhage.

y Gerstmann syndrome a neurological disorder that includes a writing disability (agraphia ordysgraphia), a lack of understanding of the rules for calculation or arithmetic (acalculia ordyscalculia), 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

y Glasgow Coma Scale (GCS) most widely used scoring system to quantify level ofconsciousness following traumatic brain injury; scores range from 3 to 15, based on the sum ofthe 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


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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

y glia supporting cells of the nervous system that provide structural and metabolic support for

the neurons; includes astrocytes, oligodendrocytes, ependymal cells, and microglia

y glioblastoma multiformeWHO grade IV astrocytoma characterized by hemorrhagic necrosis,endothelial proliferation, crossing of the corpus callosum, ring-enhancement on imaging, and

poor survival

y gliosis scar or dense fibrous network ofglial processes in an area ofCNS injury

y global aphasia impairment of language production, comprehension, and repetition due tolesion of entire perisylvian region; usually associated with right hemiparesis

y globus pallidus most medial component of thebasal ganglia and generator of most basalganglionic output

y glossopharyngeal nerve (cranial nerve IX) nerve containing motor, sensory, andparasympathetic fibers; motor fibers originate in the nucleus ambiguus and innervate the

stylopharyngeus to elevate the palate; sensory fibers originate in the superior and petrosalganglion 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 inthe inferior salivatory nucleus and carry secretory and vasodilatory fibers to the parotid gland

y Golgi tendon organs sense active stretch and via inhibitory inter-neurons inhibit the motor

neurons to provide protection against hurtful contractile forces Gowers sign maneuver used bypatients 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

y 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

y grand mal seizure see tonic-clonic seizure

y graphesthesia ability to recognize letters or numbers drawn on the finger or palm

y gray matter part of the CNS consisting ofneuronal cell bodies and dendrites

y Guillain-Barre syndrome (acute inflammatory demyelinating polyneuropathy) acute,ascending, and progressive neuropathy believed to result from an autoimmune response triggered


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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 ofpatients, there is a direct cellular immune attack on the axon itselfgustatory relating to the sense

of taste

y gyrus convoluted ridge on the outer surface of the brain caused by infolding of the cerebralcortex and bound by sulci





y habenula diencephalic structure located on the dorsomedial surface of the caudalthalamus

that receives afferents from the septal nuclei and hypothalamus via the stria medullaris andprojects to midbrainnuclei; involved in autonomic processing

y hangmans fracture fracture through bilateral pedicles of C2 via various mechanisms;

typically unstable

y hemianesthesia loss of somatosensation on one half of the body

y hemianopia loss of vision in one half of the visual field, indicating a pathological processposterior to the optic chiasm

y

hemiballismus involuntary violent flinging or jerking of a limb (or limbs) in an uncoordinatedmanner caused by a lesion of the contralateralsubthalamus

y 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, runnynose) occurring several times a day

y hemifacial spasm segmental myoclonus of muscles innervated by the facial nerve; may bedue 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

y hemiparesis weakness on one side of the body

y hemiplegiaparalysis on one side of the body

y hemiplegic migraine familial form of migraine characterized by temporary (usually < 1 hourbut occasionally lasting up to a week) hemiparesis hemisensory symptoms often associated


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with visual aura and headache; in about 50% of affected families, a defect may be found onchromosome 19 or on chromosome 1 and involves abnormal calcium channels

y heterotopia tissue occurring in an abnormal anatomical position hindbrainmedulla,pons and

cerebellum

y hippocampal formation cortical structure in the medial temporal lobe comprising the dentate

gyrus, hippocampus, and subiculum; involved in short-term declarative memory

y 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 limbicsystem, which is concerned with memory and emotion

y Hoffmans sign contraction of fingers and thumb when a stimulus is applied to a distalphalanx in that hand; indication of hyperreflexia in the upper extremity

y holoprosencephaly failure of cleavage at the rostral end of the notochord resulting in midlinefusion of the frontal lobes, midline facial abnormalities, and often hydrocephalus and

heterotopiasHomer-Wright rosette halo of cells surrounding a central lumen containingneuropil; found in medulloblastomas and PNETs

y Horner's syndromeptosis, miosis, and anhidrosisipsilateral to damaged sympathetic nervefibers

y H-reflex electrical equivalent of the monosynaptic stretch reflex elicited by selectively

stimulating the Ia fibers of the posterior tibial or median nerve

y Hunt and Hess scale scale for grading clinical status in patients with nontraumaticsubarachnoid hemorrhage that 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 palsy2

Drowsiness / confusion, mild focal neurologic deficit 3

Stupor, moderate-severe hemiparesis 4

coma, decerebrate posturing 5

y Huntington disease fatal autosomal dominant neurodegenerative disorder characterized bychorea and progressive dementia; due to a trinucleotide CAG-repeat mutation on chromosome 4

y hydranencephalybirth defect in which the majority of the cerebral hemispheres and striatumare absent and replaced by sacs filled with cerebrospinal fluid; considered to be an extreme form

ofporencephaly


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y hydrocephalus literally "water on the brain;" increase in size of ventricles and amount ofcerebrospinal fluid in the brain

y hyperacusis abnormally increased sensitivity to sound

y hyperpathia exaggerated response to painful stimuli

y hypersomnolence see excessive daytime sleepiness

y hypertensive hemorrhage intraparenchymal hemorrhage with a predilection to occur deep inthe cerebral hemispheres, especially in theputamen, thalamus, and deep white matter, as well as

thepons and cerebellum. These sites are all supplied by small penetrating arteries that are subjectto high sheer stress and have no collaterals, making them vulnerable to the effects of increased

blood pressure

y hypertonicity increase in passive muscle resistance, such as spasticity orrigidity

y hypertropia an eye with strabismus that deviates up

y hypnagogic hallucination vivid dreamlike hallucination that occurs as one is falling asleep;one of the symptoms ofnarcolepsy, but also experienced by some non-narcoleptic individuals

y hypnic headache indomethacin-responsive headache disorder characterized by diffuse,throbbing headache arising exclusively during sleep, typically between 1:00 and 3:00 AM

y hypnic jerk sensation of falling, and then "jerking" awake just as one drifts to sleep

y hypnopompic hallucination vivid dreamlike hallucination that occurs as one is waking up;

one of the symptoms ofnarcolepsy, but also experienced by some non-narcoleptic individuals

y 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 sideand deviation of the tongue at rest away from the paralyzed side; nucleus is located in the

medulla

y hypomimia see facial masking

y

hypophysis seepituitary gland

y hypothalamus basal part of the diencephalon that controls hunger, thirst, body temperature,and various metabolic processes, including the maintaining of water balance

y hypotonicity reduction in passive muscle resistance

y hypotropia an eye with strabismus that deviates down


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y hypoxia reduction in the supply of oxygen to the brain or other vital organ

y hypsarhythmia abnormal EEG pattern of excessive slow activity and multiple areas ofepileptiform activity; associated with infantile spasms

measurement of the eyes ability to 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 and



y ice cream headache nickname given to headaches that are cold induced; common in migraine

y ice-pick headacheindomethacin-responsive headache disorder characterized by momentary,sharp, and/or jabbing pain that occurs either once or several times a day at irregular intervals

y

ictus sudden attack, stroke, orseizure

y idiopathic occurring without known cause; in the context ofepilepsy, indicates cases in whichno lesion is found and a genetic cause is presumed

y 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)

y incisura fissure that separates the uncus from the apex of the temporal lobe

y incyclotorsion (a.k.a. intorsion): cyclotorsion of an eye such that the superior pole rotates

inward

y indomethacin-responsive headache class of primary headache disorders characterized by aprompt 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

y infantile spasms form ofcryptogenic generalized epilepsy characterized by sudden, forcefulforward flexion of the trunk and extension of the arms

y infarction permanent tissue damage and death of all cellular elements (neurons, glia, vessels)due to prolonged or severe ischemia

y inferior cerebellar peduncle (restiform body) paired bundle of fibers traveling to and from

the cerebellum; afferent fibers from the dorsal spinocerebellar tract carryproprioceptiveinformation from the upper body; efferent fibers travel to the vestibular nuclei in the dorsal

brainstem


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y inferior colliculuspaired structures on the dorsal surface of the caudalmidbrain overlying thecerebral aqueduct that process and relay auditory signals frombrainstem centers to the medial

geniculate nucleus of the thalamus; with the superior collicui, make up the tectum and thequadrigeminal bodies

y inferior olivary nucleusprominent nucleus in the ventral medulla located just lateral anddorsal to the medullarypyramids; source of climbing fibers that provide a critical input to the

cerebellum involved in Purkinje cell plasticity and motor learning

y infratentorial below the tentorium cerebelli, i.e.,brainstem and cerebellum

y infundibulum connection between the hypothalamus and thepituitary gland (also called the

"pituitary stalk"); contains the hypophyseal portal veins and the axons ofhypothalamicneurons

that project to the posteriorpituitary

y insomnia difficulty with falling asleep or staying asleep

y insulacerebral cortex lying in the depths of the Sylvian fissure and involved in gustatory,

visceral sensory, and emotional processing

y intention tremor tremorwhose amplitude increases as the affected body part (typically a

finger) nears an intended target and that may the targeted object to be missed; typically resultsfrom damage to the cerebellum or its connections

y internal capsulebroad compact band ofefferent and afferent fibers that travel to or from thecerebral cortex; flanked medially by the thalamus and caudate and laterally by the lentiform

nucleus

y internal carotid artery artery that arises from the common carotid artery at the upper borderof the thyroid cartilage and terminates in the middle cranial fossa by dividing into the anteriorcerebral artery and the middle cerebral artery; constitutes the anterior circulation of the brain

y inter-neuron neurons that receives input from one neurons and projects to anotherneuronswithin spinal cord, allowing a greater degree of complexity of movement control

y internuclear ophthalmoplegia failure of adduction of one eye and abducting nystagmus of

the other eye due to a lesion of the medial longitudinal fasciculus

y 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 millimetersof mercury (mmHg); normally < 20 mm/Hg

y intrathecal space (subarachnoid space) space surrounding the brain and spinal cord thatcontains cerebrospinal fluidintraventricular hemorrhage (IVH)bleeding in the ventricles


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especially from fragile blood vessels in premature infants; in adults may accompany intracerebralorsubarachnoid hemorrhage

y ipsilateral located on the same side of the body (brain)

y ischemia impairment of tissue function due to a reduction in blood supply relative tometabolic demand

y ischemic penumbra seepenumbra





y Jacksonian march contiguous spread of electrical discharges through superficial cortex

occurring with some seizures manifested by spread of muscular jerks to contiguous anatomicalareas, 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 familythat producesprogressive multifocal leukoencephalopathy; JC stands for the initials of the first

patient described with the virus

y Jefferson fractureburst fracture of the anterior and posterior arches of C1 due to axial

loading; typically stable

yjitter 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

yjuvenile myoclonic epilepsy (JME)primary generalized epilepsy syndrome usuallybeginning between ages 5 to 17 years, characterized by myoclonic (muscle-jerk), absence, andtonic-clonic seizures





y 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 includelocalization of epileptic discharges and localization ofeloquent cortex or surgical planning

y mammillary bodiespair ofnuclei in the posterior, ventral and medial hypothalamus thatreceive hippocampal inputs via the fornix and project to anteriornucleus of the thalamus and the

tegmentum of the midbrain andpons; involved in memory processing


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y Marcus-Gunn pupil see afferent pupillary defect

y mass effect structural damage due to a lesions bulk (e.g., tumor, infarct, or hemorrhage), theblockage of fluid movement (e.g., compression of a ventricle), or excessive accumulation offluid

y medial geniculate nucleus nucleus of the posterior, dorsal thalamus that receives auditoryinput from the inferior colliculus and relays this information to the primary auditory cortex

(Brodmann's areas 41 & 42) in the superior temporal gyrus.

y medial lemniscus ascending axonal tract in thebrainstem that carries tactile andproprioceptive information from the dorsal columnnuclei to the ventral posterior lateral nucleusof the thalamus

y medial longitudinal fasciculuspathway connecting the ipsilateral 3rd nerve nucleus in the

midbrain to the contralateral 6th nerve nucleus in thepons for ocular motor control

y medication overuse headache (analgesic rebound headache) headache disorder

characterized by headache that is present on 15 or more days per month in association with theuse 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 atleast three months; headache resolves or reverts to its previous patterns within two months after

discontinuation of the drug

y medulla a part of the brainstem that helps regulate respiration and other behaviors

y medulloblastoma aggressive WHO grade IV primitive neuroepithelial tumor of children and

young adults typically involving theposterior fossa sometimes with cerebrospinal fluid seeding(drop metastases); characterized histologically by small blue cells and Homer Wright rosettes

y medulla oblongata (myelencephalon) caudal aspect of thebrainstem located between thepons and the spinal cord

y megalencephaly abnormally large, heavy, and usually malfunctioning brain; thought to berelated to a disturbance in the regulation of cell reproduction or proliferation

y Meissner corpuscles dermal mechanoreceptors that subserve light touch sensation

y MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes)

mitochondrial disorder characterized by hearing loss, episodic vomiting, and recurrent cerebralinsults resembling strokes and causing hemiparesis, hemianopia, orcortical blindness

y meningeal carcinomatosis diffuse infiltration of the meninges by metastatic tumor cells oftenwith positive cerebrospinal fluid cytology


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y meninges three distinct connective tissue membranes (from outer to inner: dura, arachnoid,andpia mater) that enclose and protect the central nervous system

y meningioma slow-growing WHO grade I meningeal neoplasm that has an extra-axial locationand often shows a dural tail sign and hyperostosis of adjacent skull; characterized histologically

by whorls and psammoma bodies

y meningitis inflammation ofmeninges and spinal fluid

y meningocele form ofspina bifida in which there is herniation of only meninges (no spinal

cordparenchyma) through defective posterior arches meninx singular form ofmeninges

y menstrual (catamenial) migraine migraine occurring between one day before and four days

after the onset of menses; thought to be due to estrogen withdrawal

y Merkel cells disk-shaped receptor endings in the skin believed to be involved with the

sensation of fine touch

y mesencephalon see midbrain

y mesial temporal sclerosis hippocampal scarring and volume loss; most common cause oftemporal lobe epilepsy

y Mesulam syndrome eponym forprimary progressive aphasia

y metachromatic leukodystrophy autosomal recessive disease associated with large confluentareas of discolored gelatinouswhite mattercaused by deficiency of the enzyme arylsulfatase A,

which is necessary for the degradation of sulfatide, a myelin constituent

y Meyers looppart of the optic radiations that fans out into the temporal lobe and carries

information from the upper visual world

y 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

y microglia bone marrow derived phagocytic cells that are involved in immune reactions in theCNSmicroglial nodules formation of clusters of activated microglia around foci of necroticbrain tissue

y micrographia small, cramped handwriting

y midbrain (mesencephalon) rostral aspect of thebrainstem located between thepons and thediencephalon


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y middle cerebellar peduncle (brachium pontis) paired bundle of fibers originating from thepontine nuclei, decussating in the base of thepons, and ending in the contralateral cerebellar

cortex

y middle cerebral arterybranch of the internal carotid artery; supplies blood to the entire

lateral aspect of each hemisphere including the lateral motor strip, lateral sensory strip, languageareas,putamen, globus pallidus, and internal capsule

y middle cranial fossabutterfly-shaped portion of the internal base of the skull housing thetemporal lobes laterally and thepituitary centrally

y migraine headache attacks lasting 4-72 hours consisting of moderate to severe intensityunilateral, pulsating head pain that is aggravated by routine physical activity, inhibits daily

activities, and is associated with nausea/vomiting,photophobia, andphonophobia

y 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

y migraine with aura (classic migraine) migraine attack associated with reversible aura

symptoms indicative of focal CNS dysfunction; the aura (scintillating scotoma, vertigo,paresthesias,p

abducens nerve

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