Glossary of Stroke Terms Part 1

Glossary of Neurological Terms

• abducens nerve (cranial nerve VI) motor nerve innervating the lateral rectus muscle, which abducts the eye; lesions of the nucleus, which is located in the dorsal pons, produce a horizontal gaze palsy; nerve fibers exit the ventromedial pons and because of their long course are vulnerable to damage by mass lesions/increasedintracranial pressure
• abduct move away from the saggittal plane of the body
• absence seizure (petit mal seizure) generalized seizure characterized by abrupt cessation of ongoing activity with a blank stare and lost or impaired consciousness lasting on average 10-20 seconds
• abulia loss of will, impulse, and decision-making ability
• acalculia "inability to calculate" or difficulty with arithmetic; may be the result of damage to the angular gyrusin the hemisphere dominant for speech and language
• acephalic migraine migraine variant consisting of the migraine aura without the headache; also known as migraine equivalent accommodation adjustment of the focal length of the lens of the eye in order to keep objects at varying distances in focus on the retina
• acrocephaly action potential see brachycephaly
• action potential rapid, transient, all-or-none nerve impulse initiated at the axon hillock; electrical signal by which the brain receives, analyzes, and conveys information
• action tremor tremor that appears during movement of the affected body part
• activities of daily living (ADLs) activities a person performs for self-care (feeding, grooming, bathing, dressing), work, homemaking, and leisure; ability to perform ADLs is often used as a measure of ability/disability
• activity limitations difficulties an individual may have in executing specific tasks or actions (e.g., walking independently).
• acute developing over minutes to hours; implies acute metabolic dysfunction (e.g., ischemia, seizure )
• Acute Disseminated Encephalomyelitis (ADEM) acute, classically monophasic demyelinative disease of theCNS that may follow a viral syndrome or vaccination or no identifiable predisposing cause
• adduct move towards the saggittal plane of the body
• Adie’s syndrome association of Adie’s tonic pupil with absence of muscle stretch reflexes
• Adie’s tonic pupil irregularly dilated pupil exhibiting minimal or no reaction to light, slow reaction to accommodation, and hypersensitivity to pilocarpine; typically idiopathic and most often seen in young women
• adrenoleukodystrophy typically X-linked recessive demyelinative disease ± adrenal dysfunction due to accumulation of very long chain fatty acids
• afferent sensory pathway proceeding toward the CNS from the peripheral receptor organs
• afferent pupillary defect (Marcus-Gunn pupil) pupillary dilation in the eye with a pre-chiasmic optic pathway lesion (e.g., optic neuritis) in response to shining a light in the damaged eye after first shining it in the normal eye
• ageusia impaired sense of taste
• agnosia inability to recognize and interpret objects, people, sounds, or smells despite intact primary sense organs (e.g., inability to identify a sound despite intact hearing); typically results from damage to the occipital or parietal lobe
• agraphia inability to communicate ideas in written language not due to mechanical dysfunction; typically results from damage to the parietal lobe.
• akathisia motor restlessness; inability to sit still
• akinesia paucity of movement akinetic mutism disorder of consciousness characterized by periods of sleep and periods of wakefulness during which the patient lies with eyes open but is unresponsive, mute, and immobile; often due to frontal lobe damage
• alexia inability to read, usually due to a lesion of dominant occipitotemporal cortex
• alien hand syndrome syndrome characterized by the involuntary movement of a single upper limb in conjunction with the experience of estrangement from or personification of the movements of the limb; often seen in corticobasal degeneration allodynia condition in which an ordinarily painless stimulus is experienced as being painful
• alpha motor neurons large motor neurons that innervate extrafusal skeletal muscle fibers alpha-synucleinprotein expressed predominantly in the CNS that when aggregated, can result in neurodegenerative diseases such as Parkinson disease, dementia with Lewy bodies, and multisystems atrophy
• Alzheimer’s disease most common cause of dementia in older adults; a neurodegenerative disease characterized by the gradual loss of cognitive ability in association with the neuropathological findings of abnormal protein aggregates (neuritic plaques and neurofibrillary tangles) and neuron loss in the cerebral cortex
• amaurosis fugax temporary loss of vision in one eye due to impairment of blood supply through the internal carotid artery or the ophthalmic artery
• amblyopia developmental abnormality in which a child fails to develop sharp visual acuity
• amygdala telencephalic gray matter structure located in the anterior portion of the medial temporal lobe involved in emotion, cognition and the regulation of autonomic processes; part of the limbic system
• amyotrophic lateral sclerosis (Lou Gehrig’s disease) inexorably progressive and fatal disease of unknown cause characterized by slowly progressive degeneration of upper and lower motor neurons
• analgesia loss of pain sensation
• anencephaly (aprosencephaly) CNS malformation involving failure of closure of the cephalic end of the neural tube, resulting in absence of the forebrain and cerebrum; rudimentary brainstem may be present so that reflex actions such as breathing and responses to sound or touch may occur
• aneurysm (brain aneurysm, cerebral aneurysm) a bulging formation on an artery, usually caused by hypertension or an excessive amount of fatty deposits
• angular gyrus gyrus located immediately posterior to the supramarginal gyrus at the superior edge of the temporal lobe and involved in recognition of visual symbol; lesions can result in alexia and agraphia
• anhidrosis absence of sweating
• anisocoria pupillary asymmetry
• ankle-foot orthosis (AFO) brace that is worn on the lower leg and foot to support the ankle and correct foot drop
• anomia inability to name objects or to recognize written or spoken names of objects
• anosmia loss of sense of smell
• anosognosia lack of awareness of or indifference to one’s own neurological deficit, seen with nondominant parietal lobe lesions
• anterior cerebral artery a branch of the internal carotid artery; supplies blood to the medial aspect of thecerebral cortex (leg area predominant), some areas of the frontal lobe, corpus callosum, caudate, and the anterior limb of the internal capsule
• anterior commissure one of the three major groups of commissural fibers that courses through the basal ganglia and cross the midline in the anterior forebrain to interconnect the olfactory bulbs, amygdala, andhippocampal areas, among others
• anterior communicating artery branch of the internal carotid artery that joins together the paired anterior cerebral arteries
• anterior cord syndrome spinal cord injury syndrome associated with damage to the anterior 2/3 of the spinal cord, often due to occlusion of the anterior spinal artery resulting in bilateral paralysis, bladder dysfunction, and loss of pain sensation below the level of the lesion
• anterior cranial fossa portion of the internal base of the skull housing the frontal lobes
• anterior horn (ventral horn) gray matter in the front of the spinal cord that contains motor_neurons
• Anton's syndrome form of cortical blindness in which the patient is unaware of/denies the visual impairment; due to a lesion of the occipital lobe extending from primary visual cortex into visual association cortex
• aphasia syndrome of disordered expression or comprehension of spoken and/or written language caused by brain injury; see also non-fluent, fluent, conduction, global, transcortical motor, and transcortical sensory aphasia
• aphemia inability to speak words despite being able to make other sounds
• aphonia complete loss of voice
• apnea test part of the “brain death exam”; verifies lack of responsiveness to carbon dioxide (paCO2 > 60 mm Hg) in the presence of respiratory acidosis (pH < 7.3)
• apraxia impaired planning/sequencing of movement that is not due to weakness, incoordination, or sensory loss. Although the movements cannot be performed for a specific situation, they may be performed under other circumstances (e.g., inability to lift feet off the floor when attempting to walk but preserved ability to perform bicycling movements of the legs while lying in bed). Results from dissociation of parts of the cerebrumand is often associated with parietal lobe lesions. aprosencephaly see anencephaly
• arachnoid middle layer of the meninges covering the brain and spinal cord
• arachnoid granulations (arachnoid villi) branched tufts of arachnoid that project through the dura mater into the venous sinuses and function to return CSF to the systemic circulation
• arachnoid villi diverticula of the arachnoid mater in the subarachnoid space that extend into the veins and venous sinuses of the dura; a major pathway for the drainage of cerebrospinal fluid and transport across the endothelium into the blood.
• arcuate fasciculus pathway connecting Wernicke’s area in the posterior left superior temporal gyrus to Broca’s area in the left inferior frontal lobe; lesion results in impaired repetition
• area postrema chemoreceptor trigger zone for vomiting that is located on the dorsal surface of the medulla
• Argyll-Robertson pupil pupil exhibiting light-near dissociation due to a lesion in the midbrain periaqueductal gray matter caused by tertiary syphilis arousal abrupt change from sleep to wakefulness, or from a "deeper" stage of non-REM sleep to a "lighter" stage
• arteriovenous malformation a tangled collection of abnormal arteries and veins
• arteritis inflammation of an artery
• arthrokinetic nystagmus nystagmus induced by passive rotation of the arm of a stationary subject seated in total darkness inside a rotating drum
• ascending tract of Deiters direct pathway (lying just lateral to the medial longitudinal fasciculus) from the vestibular nuclei to the ipsilateral medial rectus subnucleus; clinical significance of this pathway is unclear
• aseptic meningitis syndrome characterized by headache, neck stiffness, low grade fever, and Cerebro Spinal Fluid lymphocytic pleocytosis in the absence of an acute bacterial pathogen; often used synonymously with viral meningitis, but also incudes meningeal inflammation due to various drugs (e.g., NSAIDs) or diagnostic procedures (e.g., angiography); atypical bacterial, fungal, parasitic, or parameningeal infection; neoplastic processes; and various systemic disorders
• asomatognosia inability to recognize part of one’s own body, seen with nondominant parietal lobe (or less commonly premotor cortex) lesions
• associated reactions movements of body parts other than the ones that are intended to move, often increased with increased effort
• association cortex cortical areas involved in higher order processing of sensory information and integration of multiple sensory and sensorimotor modalities astasia inability to stand because of motor incoordination
• astasia-abasia functional stance and gait characterized by bizarre movements, typically swaying wildly and nearly falling, but then recovering at the last minute
• asterixis sudden palmar flapping movement of the hands at the wrists; indicative of metabolic encephalopathy
• astrocytes CNS glia that function to orient neuroblast migration in the cerebral and cerebellar hemispheres, provide mechanical support, react to injury, insulate synaptic surfaces, provide a source and sink for extracellular potassium, and uptake neurotransmitters to terminate their synaptic action astrocytoma most common central nervous system tumor derived from astrocytes astrocytosis reaction of astrocytes to neuronal injury characterized by an increase in the number and size of astrocytes (primary reaction) and cytoplasmic changes including increased glial filaments and glassy eosinophilic cytoplasm followed by formation of a dense gliotic scar (secondary reaction)
• ataxia incoordination of movement usually due to disease of cerebellar or sensory pathways
• athetosis involuntary, slow, writhing movements
• atonia loss of muscle tone
• atonic seizure (drop attack) generalized seizure characterized by sudden loss of muscle tone and strength; may cause the head to drop suddenly, objects to fall from the hands, or the legs to lose strength, with falling and potential injury
• aura
• warning symptom (e.g., of vision, smell or perception) occurring prior to a spell such as a migraine or seizure; implies focal brain disturbance
• automatism mechanical, seemingly aimless behavior (e.g., lip smacking or picking at clothes) characteristic ofcomplex partial seizures
• autonomic pertaining to the autonomic nervous system, which controls bodily functions that are not under conscious control (e.g., heartbeat, breathing, sweating)
• autonomic nervous system part of the peripheral nervous system that regulates visceral function and homeostasis independent of voluntary control
• autoregulation physiological process by which blood vessels change caliber to maintain constant cerebral blood flow over a wide range of cerebral perfusion pressures axial transverse plane producing a cross-section of the body or head
• axon long, slender projection from the neruonal cell body that is specialized for the conduction of information encoded in the form of action potentials
• axonal degeneration neuropathic process resulting in degeneration of the axon and its myelin sheath; preferentially involves the distal portion of the axon ("dying back neuropathy")
• axonal spheroid stereotypic axonal response to injury consisting of marked swelling due to accumulation of materials undergoing axonal transport
• Babinski response extension of the great toe on stimulation of the sole of the foot, signifying a lesion of thecorticospinal tract (a.k.a., upgoing toe); see also plantar response
• Balint syndrome syndrome comprising paralysis of visual fixation, optic ataxia, and impairment of visual fixation due to bilateral lesions of the parietal and occipital lobes
• basal ganglia large subcortical nuclear masses consisting of the caudate, putamen, globus pallidus,subthalamus, and substantia nigra; part of the motor system that permits chosen and inhibits unwanted movement basal palisading basal layer of small cells with darkly staining nuclei and little cytoplasm seen in the epithelium of craniopharyngiomas
• basilar artery large brainstem artery located on the ventral surface of the pons formed by the joining of the two vertebral arteries and bifurcating into the posterior cerebral arteries; supplies blood to cerebral circulation and ventral pons
• basilar migraine form of migraine characterized by a visual aura followed by an often occipital headache and one or more of the following symptoms: dysarthria, vertigo, tinnitus, decreased hearing, diplopia, blindness,ataxia, bilateral paresthesia, bilateral paresis, and impaired cognition
• behavioral symptom complex changes in personality and behavior
• Bell’s palsy (idiopathic facial paralysis) cranial neuritis affecting the facial nerve thought to be due to reactivation of the herpes simplex virus; results in lower motor neuron facial weakness, hyperacusis, taste disturbance, and impaired lacrimation
• Bell's phenomenon fluttering of the eyes upward when closed eyelids are opened by the examiner
• Benedikt Syndrome ipsilateral oculomotor palsy and contralateral hemichoreoathetosis due to lesion of theventral midbrain tegmentum affecting the IIII nerve fascicles and the red nucleus
• Berry aneurysm small saccular aneurysm of an intracranial artery
• Binswanger’s disease (subcortical leukoencephalopathy) degenerative white matter disease producingdementia due to hypertensive microvascular changes lipohyalinosis of the small arteries and fibrinoid necrosisof the larger vessels inside the brain)
• blepharospasm excessive involuntary contraction of the orbicularis oculi sometimes resulting in functional blindness; a focal dystonia
• blood-brain barrier specialized system of capillary endothelial cells that strictly limits transport into the brain through both physical (tight junctions) and metabolic (enzymes) barriers
• borderzone infarct see watershed infarct
• brachial relating to the arm
• brachium anatomical structure comprising a collection of axons that resemble an arm
• brachium conjunctivum see superior cerebellar peduncle
• brachium pontis see middle cerebellar peduncle
• brachycephaly (acrocephaly) premature fusion of bilateral coronal sutures producing a foreshortened skull
• bradykinesia slowed movement due to dysfunction of the basal ganglia and related structures
• bradyphrenia slowing of thought processes that can occur in Parkinson disease or as a side effect of antipsychotic medications
• brain death see death by neurological criteria
• brainstem medulla, pons, and midbrain
• brainstem auditory evoked potentials (BAEP) series of waves that reflect sequential activation of neural structures along the auditory pathways following a brief click or tone transmitted via an earphone or headphone and measured by surface electrodes placed at the vertex of the scalp and ear lobes; provides information regarding auditory function and hearing sensitivity and used to screen for retrocochlear pathology (e.g., acousticneuroma), universal newborn hearing screening, and intraoperative monitoring
• brain death
• see death by neurological criteria
• Broca’s aphasia see non-fluent aphasia
• Brodmann's areas distinct regions of the cerebral cortex recognized by variations in cell size, density, and thickness of the cortical layers
• Brown Sequard syndrome spinal cord injury syndrome associated with damage to one lateral half of the spinal cord (spinal hemisection) resulting in ipsilateral weakness and loss of vibration proprioception andcontralateral loss of pain sensation
• Brudzinski’s sign involuntary flexion of the hips in response to passive flexion of the neck; indicative ofmeningeal irritation
• bruxism grinding one's teeth while asleep
• bulbar pertaining to the lower cranial nerve nuclei
• burst fracture compression fracture of vertebral body with expansion in sagittal and coronal planes due to axial loading; unstable and often associated with spinal cord injury
• calcarine cortex primary visual cortex located in the occipital lobe (striate area 17)
• carotid sinus arterial baroreceptor located at the bifurcation of the external and internal carotid arteries that regulates arterial pressure and heart rate in response to changes in stretch and transmural pressure
• carphologia see floccillation
• catamenial referring to menses; with regard to women with epilepsy or migraine, a tendency forseizures/migraines to occur around the time of menses
• cataplexy sudden loss of postural tone, often triggered by an emotional stimulus and resulting in falls to the floor; seen in narcolepsy cauda equina (“horse’s tail”) collection of intradural spinal nerve roots caudal to the spinal cord that supply the lower limbs and pelvis; since this structure is part of the peripheral nervous system, lesions produce lower motor neuron deficits
• caudal toward the tail
• caudate portion of the basal ganglia that lies in the floor of the lateral ventricle
• cavernoma (cavernous malformation) vascular malformations composed primarily of large venous channels without a clear-cut arterial component
• cavernous sinus paired, venous structures located on either side of the sella turcica that receive blood from the superior and inferior orbital veins and drain into the superior and inferior petrosal sinuses; contains thecarotid artery and its sympathetic plexus, the oculomotor nerves (III, IV, VI), and the ophthalmic branch of V; lesions typically result in ophthalmoplegia, orbital congestion, and proptosis
• central chromatolysis regenerative response to axonal injury consisting of neuronal swelling, nuclear eccentricity, and loss of Nissl substance
• central cord syndrome spinal cord injury syndrome associated with damage to the central portion of the spinal cord characterized by bilateral weakness of distal>proximal muscles in the arm>leg, bladder dysfunction, and a variable degree of sensory loss below the level of injury
• central herniation downward displacement of the cerebral hemispheres pushing the diencephalon andmidbrain through the tentorial notch; symptoms classically follow a rostrocaudal deterioration
• central nervous system (CNS) brain and spinal cord
• central pain syndrome intense pain arising from injury to the central nervous system, most often in patients who have had a stroke, multiple sclerosis, or brain injury.
• central sulcus prominent sulcus on the dorsolateral aspect of the cerebral hemispheres formed by the precentral and postcentral gyri; defines the boundary between the frontal and parietal lobes
• centrum semiovale expansive region of white matter in the dorsal core of the frontal and parietal lobes, named because of its central position in the forebrain and its semi-oval shape
• cephalic relating to the head
• cerebellar peduncle three major white matter structures containing #efferent and afferent axons of thecerebellum; named the inferior, middle, and superior cerebellar peduncles
• cerebellar tonsil lateral portions of the uvula located in the posterior lobe of the cerebellum
• cerebellopontine angle space located at the junction of the cerebellum, pons, and medulla containing cranial nerves V-XI, blood vessels, the flocculus of the cerebellum, and choroid plexus
• cerebellum brain structure in posterior fossa that coordinates the many muscles active in any given movement; receives input from spinal cord and cerebral cortex and projects to postural and voluntary motor control systems and red nucleus
• cerebral amyloid angiopathy (congophilic angiopathy) vascular disorder in which beta amyloid protein is deposited within the media and adventitia of small- to medium-sized meningeal and cortical blood vessels, causing them to become brittle and break; important cause of predominantly lobar intracerebral hemorrhage in the elderly
• cerebral aqueduct portion of the ventricular system that lies in the dorsal midbrain and connects the third and fourth ventricles
• cerebral arteriosclerosis thickening and hardening of the arteries within the brain
• cerebral atherosclerosis build-up of fatty deposits in the inner wall of cerebral arteries; form of cerebral arteriosclerosis
• cerebral atrophy the shrinking of the brain or brain cells.
• cerebral autosomal dominant arteriopathy with subcortical infarcts & leukoencephalopathy (CADASIL) familial arterial disease of the brain caused by mutations in the Notch3 gene and consisting of recurrent subcortical strokes starting in midadult life, dementia, depression, and migraine
• cerebral cortex highly convoluted layer of gray matter that constitutes the outermost layer of the cerebrumand is responsible for integrating sensory impulses and for higher intellectual functions
• cerebral hemisphere symmetrical half of the cerebrum as separated by the sagittal sulcus and containing thecerebral cortex, basal ganglia, hippocampus, and amygdala
• cerebral peduncle (crus cerebri) white matter tracts (corticospinal and corticobulbar) on the ventral surface of the midbrain containing the efferent axons of cerebral cortex that project to brainstem and spinal cord
• cerebral perfusion pressure (CPP) mean arterial pressure (MAP) – intracranial pressure (ICP)
• cerebral salt wasting centrally-mediated hypovolemic hyponatremia associated with negative sodium balance that occurs in approximately 30-50% of patients with subarachnoid hemorrhage despite their being given maintenance volumes of fluids; excessive sodium loss is thought to be due to impaired sodium reabsorption in the proximal tubule and may be caused by disruption of sympathetic input to the kidneys, production of a circulating natriuretic factor, or both
• cerebritis inflammation of the brain
• cerebrospinal fluid (CSF) clear, colorless fluid bathing the entire surface of the CNS, most of which is secreted by the choroid plexus and the remainder by brain capillaries; flows through the ventricles and out into the subarachnoid space via the foramen of Magendie in the midline and the two foramina of Luschka at the lateral margins of the roof of the 4th ventricle, then is absorbed through the arachnoid villi in the walls of dural sinuses and returned to the systemic circulation
• cerebrum anterior portion of the brain consisting of the two cerebral hemispheres that each contain four lobes
• Charcot-Bouchard aneurysm aneurysmal dilation of small intraparenchymal vessels commonly seen in the brains of patients with hypertensive hemorrhage
• Charcot joint progressive destruction and deformity of bone and soft tissue at weight bearing joints due to severe sensory or autonomic neuropathy cheiro relating to the hand
• Chiari malformation CNS disorder characterized by cerebellar elongation and protrusion through the foramen magnum into the cervical spinal cord. Type I consists of caudal displacement of the medulla and inferior pole of the cerebellar hemispheres through the foramen magnum. Type II=type I + hydrocephalus and lumbosacralspina bifida. Type III involves herniation of the entire cerebellum through the foramen magnum with a cervicalspina bifida cystica. Type IV involves cerebellar hypoplasia
• chorea involuntary, irregular, rapid, jerking movements
• choroid plexus intraventricular structure that secretes cerebrospinal fluid
• choroid plexus papilloma histologically benign intracranial tumor of neuroectodermal origin that is most commonly located in a ventricle (lateral>fourth>third), where it often presents with non-communicating hydrocephalus due to overproduction of CSF; may also be seen in the cerebellopontine angle
• chronic daily headache headache disorder consisting of frequent headache occurring 15 or more days per month and including headache associated with medication overuse
• chronic paroxysmal hemicrania indomethacin-responsive headache disorder characterized by the occurrence of multiple daily attacks lasting 5 to 30 minutes of severe unilateral head pain often associated withautonomic phenomenon (eye tearing, eye redness, eyelid edema, nasal congestion, runny nose); also known as atypical cluster headache
• chronic-progressive developing over months to years; implies gradual deterioration as occurs with degenerative diseases like Alzheimer disease, Huntington disease, etc.
• cingulate gyrus cortical component of the limbic system located on the medial aspect of the hemisphere superior to the corpus callosum; involved in emotional and cognitive processing
• cingulate herniation horizontal displacement of a cerebral hemisphere due to an expanding lesion that forces the cingulate gyrus under the falx cerebri, compressing the internal cerebral vein and the 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 and the basilar artery come together, allowing blood to be redistributed to the anterior,middle, and posterior cerebral arteries
• “clasp knife” spring-like resistance to passive extension at the elbow or flexion at the knee that increases up to a certain length and force before suddenly relaxing as the Golgi tendon organ is activated; sign of spasticity
• classic migraine see migraine with aura
• Claude Syndrome ipsilateral oculomotor palsy and contralateral ataxia and hemichoreoathetosis due to adorsal midbrain tegmental lesion affecting the III nerve fascicles, superior cerebellar peduncle, and red nucleus
• claustrum thin plate of gray matter lying in the white matter between the insula and the basal ganglia that modulates cortical activity
• clay shoveler’s fracture typically stable fracture through a spinous process due to hyperextension injury
• clonic seizure generalized seizure characterized by jerking movements on both sides of the body
• clonus rhythmic contraction relaxation tremor due to cyclic alternations of the spindle stretch reflex and theGolgi tendon organ reflex; indicative of exaggerated stretch reflexes
• cluster headache primary headache syndrome characterized by intense, unilateral orbital, supraorbital, and/or temporal pain lasting 15-180 minutes and occurring in "clusters" up to several times per day for a period of one or more months before going into "remission" for months or years; diagnosis requires one or more of the following autonomic abnormalities ipsilateral to the headache: conjunctival injection, lacrimation, ptosis, miosis, eyelid edema, nasal congestion, rhinorrhea, or facial sweating CNS central nervous system
• CNS metastasis metastatic tumors typically spread by a hematogenous route and found at the junction between gray matter and white matter where they are trapped by the acute angle branching of the microvasculature
• cogwheeling ratchety movement due to superimposition of tremor on rigidity
• coital headache indomethacin-responsive headache disorder characterized by sudden, severe, throbbing, occipital headache that occurs just before or during orgasm
• cold calorics see oculovestibular response
• coma state of unarousable unresponsiveness with closed eyes, no speech, and no purposeful movements
• common carotid artery artery that arises from the brachiocephalic artery on the right and from the aortic arch on the left, ascending in the neck and dividing at the upper border of the thyroid cartilage into the external andinternal carotid arteries to supply the head and neck
• common migraine see migraine without aura communicating hydrocephalus blockage of CSF flow outside the ventricular system, either at the level of the arachnoid granulations or because of overproduction of CSF (e.g., from a choroid plexus papilloma) that exceeds the rate of absorption
• complex partial seizure partial seizure in which consciousness or awareness is impaired; epileptic discharge either originates in limbic structures (hippocampus) or spreads to them from 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 are coordinated or sequential patterns of movement such as twirling a pencil or touching other people
• concussion traumatic closed head injury that results in temporary impairment of neurological function, e.g., transient loss of consciousness
• conduction aphasia selective impairment of the ability to repeat due to a lesion of the arcuate fasciculus, which connects Wernicke’s area to Broca’s area
• conduction block failure of impulse conduction along an anatomically intact axon; characteristic ofdemyelinating neuropathy
• contracoup opposite to the site of impact
• contracture permanent shortening of the muscles and tendons adjacent to a joint, which can result from severe spasticity and interferes with normal movement around the affected joint
• contralateral located on the opposite side of the body (brain)
• contusion edematous brain lesion containing punctuate parenchymal hemorrhages on the surface of the brain that may extend bidirectionally into the white matter and the subdural and subarachnoid spaces; occur at the site of impact (coup contusion) with direct trauma and at a site opposite to the site of impact (contracoupcontusion) with acceleration/deceleration injury
• conus medullaris caudal-most part of the spinal cord located between the first and second lumbar vertebrae. Since this structure is part of the spinal cord but is in close proximity to spinal nerve roots, lesions often produce both upper motor neuron and lower motor neuron deficits
• convergence coordinated inward movement of the eyes in order to fixate on a near object convergence-retraction nystagmus form of nystagmus consisting of jerking eye movements inward and backward; associated with dorsal midbrain lesion
• coprolalia uncontrolled, often obsessive use of obscene language occasionally seen in Tourette syndrome
• coronal vertical plane from head to foot and parallel to the shoulders corona radiata fan-like arrangement of fibers projecting from all aspects of the cerebral cortex and converging toward the thalamus where they will form the internal capsule
• corpus callosum large fiber structure that makes connections between homotopic regions of the cerebral hemispheres; bend at its anterior limit is called the genu; bend at its caudal end is called the splenium; portion between the two is called the body.
• corpus striatum see striatum
• cortical referring to the cerebral cortex, the outermost layer of the cerebrum
• cortical blindness apparent lack of visual functioning in spite of anatomically and structurally intact eyes due to bilateral lesions of the primary visual cortex
• corticobasal degeneration progressive neurological disorder characterized by nerve cell loss in the cerebral cortex and basal ganglia and producing parkinsonism, dementia, visual-spatial impairment, alien hand syndrome, apraxia, and myoclonus
• corticobulbar tract axons originating in the posterior frontal lobe and projecting to lower motor neurons in the brainstem
• corticospinal tract (pyramidal tract) motor pathway responsible for voluntary movement that arises from primary motor cortex, area 6, and somatosensory cortex and descends through the corona radiata, internal capsule, cerebral peduncle, medullary pyramid (where it decussates), and spinal cord to alpha motor neurons in spinal cord gray matter
• cough headache indomethacin-responsive headache disorder characterized by transient, severe, explosive head pain upon coughing, sneezing, weight lifting, bending, or stooping
• coup lesion at the site of impact Cowdry A inclusion bodies eosinophilic nuclear inclusions surrounded by a clear halo in neurons or glial cells occurring in herpes simplex encephalitis Cowdry B inclusion bodies large glassy eosinophilic nuclear inclusions occurring in herpes simplex encephalitis
• craft palsy dystonia occurring in the setting of a highly learned skilled task, e.g., writer’s cramp, yips in golfers
• craniectomy surgical removal of a section of bone (bone flap) from the skull for the purpose of operating on the underlying tissues or relieving intracranial pressure, in which the bone flap is not replaced at the end of the procedure
• craniopharyngioma suprasellar WHO grade I tumor of children/young adults that causes significant morbidity and mortality; characterized histologically by basal palisading, wet keratin, and infiltrative fingers of tumor that make it difficult to cure cranioplasty surgical repair of a defect or deformity of the skull; replacement of a bone flap craniorachischisis totalis fatal neural tube defect consisting of total failure of neurulation; a neural plate-like structure is entirely exposed without overlying bony or dermal covering
• craniosynostosis premature closure at birth of one or more cranial sutures, which limits head growth perpendicular to the suture(s); see also brachycephaly, oxycephaly, plagiocephaly, scaphocephaly,trigonocephaly
• craniotomy surgical removal of a section of bone (bone flap) from the skull for the purpose of operating on the underlying tissues, in which the bone flap is replaced at the end of the procedure creatine kinase enzyme that catalyzes the conversion of creatine to phosphocreatine and is released into the blood by tissues—particularly muscle—that consume adenosine triphosphate (ATP) rapidly; elevated levels are seen in myopathy
• cremasteric reflex superficial (cutaneous) reflex elicited by stroking the superior and medial part of the thigh in a downward direction; normal response is contraction of the cremasteric muscle that pulls up the scrotum and testis on the side stroked; dependent on nerve roots L1 and L2
• Creutzfeldt-Jakob disease fatal prion disease characterized by spongiform changes in the brain, progressivedementia, psychiatric changes, and myoclonus; form of spongiform encephalopathy
• crossed adductor reflex reflex contraction of the adductor magnus caused by tapping the opposite knee; indication of hyperreflexia on the side of the adductor contraction; commonly thought to be due to stimulation of the adductor muscle on the hyperreflexive side through slight jarring of the pelvis
• “crossed signs” ipsilateral cranial nerve signs and contralaterallong-tract signs: implies lesion of the brainstem; sometimes used synonymously with dissociated sensory deficits due to spinal cord or brainstem lesions
• crural relating to the leg crus cerebri see cerebral peduncle
• cryptogenic occurring without known cause; in the context of epilepsy, indicates cases in which a lesion and distinct pathogenesis are presumed
• cyclotorsion (a.k.a. torsion): rotation of the eye around an anterior-posterior axis; see excyclotorsion,incyclotorsion
• Dawson’s fingers ovoid demyelinating lesions with their long axis perpendicular to the ventricular surface seen in multiple sclerosis
• death by neurological criteria irreversible loss of all brain function
• decerebrate rigidity stereotyped posture consisting of extension of all four limbs occurring with transaction between the superior collicui and inferior colliculi in the midbrain; often used synonymously with extensor posturing
• decorticate rigidity stereotyped posture consisting of flexion of the forelimbs and extension of the hindlimbs occurring with transaction between the diencephalon and midbrain; often used synonymously with flexor posturing
• decussate to cross
• deja vu feeling as if one has lived through or experienced this moment before; may occur in people without any medical problems or as a seizure aura_
• delayed sleep phase syndrome circadian rhythm disorder in which in the daily sleep/wake cycle is delayed with respect to clock time such that sleep occurs well after the conventional bedtime; common in young adults
• delirium abnormal mental state characterized by disorientation, inattention, confusion, fear, irritability, perceptual disturbance, and fluctuating level of consciousness; common with toxic and metabolic disorders and acute febrile systemic infections
• dementia acquired and sustained loss of memory and other intellectual functions that is of sufficient severity to interfere with daily functioning dementia pugilistica chronic traumatic encephalopathy caused by cumulative and repetitive head trauma and manifesting as dementia and parkinsonism
• demyelination destruction or loss of the myelin sheath surrounding axons; results in impaired nerve impulse conduction
• dendrite receiving portion of the neuron
• denervation loss of nerve supply
• dermatome distribution of sensory innervation on the skin of the body and the limbs
• diabetes insipidus inability to concentrate urine resulting from decreased secretion of antidiuretic hormone; reflects a lesion of the hypothalamic osmoreceptors, supraoptic or paraventricular nuclei, or the supraopticohypophyseal tract and may occur in transtentorial herniation due to downward traction on thehypothalamic median eminence
• diaphragma sellae thin dural membrane overlying the sella turcica that is fenestrated to allow passage of theinfundibulum
• diaschisis depression of metabolism at sites distant from, but connected with, a site of cerebral injury (e.g.,infarction) due to interruption of afferent or efferent fiber pathways
• diastematomyelia longitudinal division of the spinal cord by a septum of bone
• diencephalon thalamus, hypothalamus, subthalamic nucleus, and pineal
• diffuse axonal injury widespread damage to white matter due to rotational shearing forces with head trauma
• diffuse Lewy body disease (Lewy body dementia) form of dementia associated with fluctuating alertness, recurrent visual hallucinations, and parkinsonism and defined pathologically by cortical (as well as nigral) Lewy bodies
• diplegia see paraplegia
• diplopia double vision
• dissociated sensory deficit impairment of pain/temperature sensation with preservation of vibration/proprioception or vice versa; implies lesion of brainstem or spinal cord involving 1 sensory tract but sparing the other
• dolichocephaly see scaphocephaly
• doll’s phenomenon see oculocephalic response
• dorsal posterior
• dorsal columns ascending axonal tract running in the dorsal funiculus of the spinal cord that carries tactile andproprioceptive information to the brain; fibers cross in the ventromedial medulla to become the medial lemniscus dorsal horn see posterior horn
• dorsal motor nucleus of the vagus parasympathetic nucleus that stimulates secretion from glands of the pharynx and thoracic and abdominal viscera
• dorsal rhizotomy surgical procedure involving sectioning of the dorsal spinal nerve roots performed to reducespasticity
• dorsal root ganglion collection of cell bodies located in the intervertebral foramina that transduce sensory information into neural signals and transmit these signals to the CNS
• dose failure phenomenon in which an individual dose of medication has no effect; occurs in Parkinson diseasepossibly in association with a tablet getting stuck in the throat or delayed gastric emptying
• double simultaneous stimulation (DSS) ability to detect two stimuli applied simultaneously to opposite sides of the body; for tactile DSS, if a patient is able to identify which side is being touched when each side is touched individually, but extinguishes or neglects one of the sides when both sides are touched simultaneously; indicates dysfunction of the contralateral posterior parietal lobe
• drop metastases tumor masses in the lumbosacral spinal cord due to CSF spread of neoplastic cells (e.g.,medulloblastoma)
• duction movement of one eye
• dura mater outermost layer of the meninges covering the brain and spinal cord; consists of a thick fibrous tissue that is adherent to the inner table of the skull and forms a protective sheath in the vertebral canal
• dural tail sign tail of dural enhancement seen on CT or MRI in association with meningeal neoplasms such asmeningioma Duret hemorrhages secondary hemorrhages occurring in the diencephalon, midbrain, and ponsas downward movement of the brainstem relative to the immobile blood vessels on the surface of the brainstem results in injury to small penetrating blood vessels; sequelae of cerebral herniation
• dysarthria inability to pronounce or articulate words due to disorders of the vocal apparatus (e.g., lips, tongue, larynx)
• dysdiadochokinesia impaired ability to perform rapid alternating movements (e.g., pronation/supination of hands); indicates cerebellar dysfunction
• dysesthesia pain or discomfort in response to a stimulus (e.g., touch) that would not be expected to cause pain
• dysgeusia distorted taste perception
• dysgraphia a writing disability that results in incorrectly spelled or written words
• dyskinesia blanket term for movement disorders characterized by increased motor activity
• dyslexia disorder that limits the ability to read
• dysmetria difficulty judging and controlling the speed, distance, or power of motor actions; tendency to over- or underestimate the extent of motion needed
• dysphagia difficulty in swallowing
• dysphonia voice disorder, often related to weakness of laryngeal muscles, in which sound production is impaired
• dysraphism defective closure of a raphe, particularly the neural tube
• dyssomnia disorder in which the main complaint is about inadequate or unrefreshing sleep
• dystonia involuntary muscle spasms that produce peculiar postures of different body parts
• echolalia imitation of sounds without comprehension of their meaning
• echopraxia imitative repetition of the movements, gestures, or posture of another person occasionally seen inTourette syndrome
• Edinger-Westphal nucleus accessory nucleus of each oculomotor nerve that supplies preganglionic parasympathetic fibers for pupillary constriction and lens accommodation; located in the midline between the extraocular oculomotor nerve nuclei
• efferent motor pathway proceeding from the CNS toward the peripheral end organs
• electromyography graphical representation of the electrical activity in a muscle
• eidetic memory (photographic memory) ability to vividly recall visual images, sounds, or objects in memory with extraordinary detail
• electroencephalogram (EEG) system for recording the electrical potentials of the brain derived from electrodes attached to the scalp eloquent cortex regions of the cerebral cortex responsible for motor, sensory, language or other cognitive processing that if removed, will result in a neurological deficit; identification of eloquent cortex through brain mapping is a vital part of the planning for epilepsy surgery and resection of brain tumors and vascular malformations in order to minimize adverse outcomes from surgery
• empty sella downward displacement and compression of the pituitary gland by cerebrospinal fluid filling thesella turcica; primary empty sella syndrome occurs when a small defect in the diaphragma sellae increases pressure in the sella and compresses the pituitary; secondary empty sella syndrome occurs when the sella is empty because the pituitary has shrunken following injury, surgery, or radiation
• encephalitis inflammation of brain tissue
• encephalocele failure of bone fusion in the posterior midline of the skull resulting in a bony cleft through which meninges and/or brain parenchyma protrude encephalomalacia focal softening of the brain in areas of tissue death following cerebral infarction, infection, trauma, etc.
• encephalopathy literally, "brain suffering"; diffuse brain dysfunction that may be caused by toxins, infection, metabolic or mitochondrial disease, tumor or increased intracranial pressure, trauma, or lack of blood flow or oxygen to the brain; the hallmark is impaired level of consciousness
• endomysium innermost layer of connective tissue that forms an interstitial layer around each individual muscle fiber
endoneurium (epilemma) innermost layer of connective tissue of a peripheral nerve that forms an interstitial layer around each individual axon / Schwann cell unit
• enophthalmos recession of the eyeball within the orbit
• eosinophilic neuronal necrosis neuronal response to ischemia and hypoxia characterized by brightly eosinophilic (red) cytoplasm and nuclear shrinkage
• ependyma epithelial lining of the ventricles of the brain and the canal of the spinal cord
• ependymal cells type of glia consisting of cuboidal cells lining the adult ventricles and spinal canalependymal true rosette halo of cells surrounding an empty lumen; fairly specific for, though infrequently seen in, ependymomas
• ependymoma WHO grade II primary CNS tumor of children (involving the 4th ventricle) and young adults (involving the spinal cord); characterized histologically by perivascular pseudorosettes, ependymal true rosettes, sharp demarcation, and enhancement on CT/MRI
• ephaptic electrical conduction of a nerve impulse across a non-synaptic contact site between nerves and without the mediation of a neurotransmitter
• epilepsy chronic brain disorder of various etiologies characterized by recurrent unprovoked seizures
• epilepsy syndrome disorder defined by seizure type, clinical and EEG findings, age of onset, family history, response to therapy, and prognosis epineurium outermost layer of a peripheral nerve containing connective tissue and an anastomotic vascular network
• epithalamus dorsal posterior subdivision of the diencephalon generally considered to include the habenula, the pineal body, and the epithelial roof of the third ventricle
• esotropia an eye with strabismus that deviates inward
• essential tremor medium or high frequency (4-9 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 system’s electrical response to the stimulation of specific sensory pathways; see also somatosensory evoked potentials, brainstem auditory evoked potentials, and visual evoked potentials
• excessive daytime sleepiness (hypersomnolence) subjective difficulty in staying awake and easily falling asleep when sedentary
• excyclotorsion (a.k.a. extorsion): cyclotorsion of an eye such that the superior pole rotates outward
• executive functions higher intellectual functions such as judgment, insight, reasoning, abstraction
• exophthalmos see proptosis
• exotropia an eye with strabismus that deviates outward
• Expanded Disability Status Scale (EDSS) 20-point scale, ranging from 0 (normal examination) to 10 (death) by half-points, that measures impairment (gait is heavily emphasized); used in clinical trials of multiple sclerosis
• extensor plantar response extension of the great toe (“upgoing toe”) with fanning of the other toes in response to application of a stimulus to the skin of the foot or leg; signifies a lesion of the corticospinal tract
• extensor posturing
• stereotyped posture occurring in coma in response to stimulation in which the arms and legs extend (hips and shoulders extend, adduct, and internally rotate; knees and elbows extend; forearms hyperpronate; wrists and fingers flex; feet plantarflex and invert; and trunk extends); reflects "release" of primitive responses from the suppression of more rostral motor areas that have been damaged and is reminiscent of the decerebrate state demonstrated in animals with transection through the midbrain colliculi
• extensor response in the arm stereotyped posture occurring in coma in response to stimulation in which the upper extremity extends (shoulder extends, adducts, and internally rotates; elbow extends; forearm hyperpronates; wrist and fingers flex); may be accompanied by extension of the lower extremity (hip extends, adducts, and internally rotates; knee extends; foot plantar flexes and inverts) as in decerebrate rigidity; reflects "release" of primitive responses from the suppression of more rostral motor areas that have been damaged
• extensor spasm manifestation of spasticity in which the legs involuntarily straighten into an extended position where they remain for several minutes
• extinction see double simultaneous stimulation
• extra-axial within the skull or vertebral column but outside of the brain or spinal cord
• extrapyramidal movement disorder not involving the corticospinal tracts; typically refers to basal ganglia orcerebellar disorders
• extrasylvian outside of the area surrounding the Sylvian fissure; often used synonymously with "transcortical," as in transcortical motor aphasia and transcortical sensory aphasia
• F-wave long latency muscle action potential seen after supramaximal stimulation to a nerve
• facial masking (hypomimia) decreased facial expression due to rigidity of facial muscles
• facial nerve (cranial nerve VII) predominantly motor nerve supplying muscles of facial expression; also carries sensation (external ear, taste from anterior 2/3 of tongue) via the nervus intermedius and preganglionicparasympathetic fibers to the lacrimal, palatal, and nasal glands
• fainting
• - see syncope
• falx cerebri fold of dura mater in the sagittal sulcus between the two cerebral hemispheres
• fascicle bundle of axons (nerve fascicle) or muscle fibers (muscle fascicle) surrounded by a layer of contractile cells (perineurium for nerves or perimusium for muscles)
• fasciculation spontaneous firing of an axon resulting in a visible twitch of all the muscle fibers it contacts; indicative of denervation
• festination an involuntary tendency to take short accelerating steps in walking that can occur in Parkinson disease
• fibrillation spontaneous firing of a single muscle fiber not visible to the naked eye, indicative of denervation or irritable myopathy; seen electrographically as a brief action potential with initial positive (down) wave followed by negative (up) wave filum terminale delicate fibrous tissue structure surrounded by a few nerve fibers that extends downward from the conus medullaris to the first segment of the coccyx
• finger agnosia type of agnosia characterized by inability to identify the fingers; a component of Gerstmann syndrome
• Fisher scale scale for grading CT appearance in patients with nontraumatic subarachnoid hemorrhage; higher scores predictive of developing symptomatic cerebral vasospasm
  Description Group No subarachnoid blood detected 1 Diffuse subarachnoid blood or vertical layers 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
• febrile seizure typically benign seizure associated with high fever in children aged 3 months to 5 years
• fibrinoid necrosis brightly eosinophilic lesions in the small vessels of the brain postulated to occur because of disordered cerebral autoregulation in association with aging and hypertension; contributes to the development of lacunar infarction and hypertensive hemorrhage
• flaccidity severe form of hypotonicity
• flexor plantar response flexion (curling down) of all toes (“downgoing toe”) in response to application of a stimulus to the skin of the foot or leg; normal response flexor posturing stereotyped posture occurring incoma in response to stimulation in which the upper extremity flexes and the lower extremity extends; reflects release of primitive responses from the suppression of more rostral motor areas that have been damaged and is reminiscent of the decorticate state demonstrated in animals with transaction of corticospinal fibers above the midbrain
• flexor response in the arm stereotyped posture occurring in coma in response to stimulation in which the upper extremity flexes and the lower extremity extends; reflects release of primitive responses from the suppression of more rostral motor areas that have been damaged and is reminiscent of the decorticate state demonstrated in animals with transaction of corticospinal fibers above the midbrain
• flexor spasm often painful manifestation of spasticity in which the legs involuntarily pull upward into a clenched position for a period of a few seconds
• floccillation purposeless picking at clothing or bedding seen in delirium
• flocculus small lobe of the posterior cerebellum; comprises the lateral portion of the vestibulocerebellum
• fluent aphasia (Wernicke’s or receptive aphasia) impairment of language comprehension including impaired repetition due to lesion of the posterior left superior temporal gyrus (Brodmann area 22)
• fontanel soft membranous gap between the incompletely formed cranial bones of a fetus or an infant; the anterior fontanel (where the metopic, the two coronal, and the sagittal sutures come together), fuses at 7-19 months; the posterior fontanel (where the lambdoid and sagittal sutures come together) is often fused at birthforamen magnum large opening at the base of the skull through which the spinal cord and vertebral arteriespass from the vertebral cavity into the cranial cavity
foramen of Magendie midline exit of CSF from the fourth ventricle into the subarachnoid space
• foramen of Monro permits communication of the third ventricle with each of the lateral ventricles on anterolateral aspect of the third ventricle
foramina of Luschka lateral exits of CSF from either side of the fourth ventricles into the subarachnoid space
• forebrain portion of the central nervous system derived from prosencephalon; commonly used to denotecerebral hemispheres and diencephalon
• fornix white matter structure containing axons that connect the hippocampus to the hypothalamus and septalnuclei
• fortification spectrum (teichopsia) complex visual migraine aura consisting of zig-zag lines or an arc of scintillating lights forming into a herringbone pattern and expanding to encompass an increasing portion of a visual hemifield
• Foster-Kennedy syndrome ipsilateral anosmia, ipsilateral optic atrophy, and contralateral papilledema due to frontal lobe or olfactory groove mass lesion
• fovea center most part of the macula responsible for detailed central vision
• Foville syndrome ipsilateral lateral gaze palsy, ipsilateral peripheral facial palsy, and contralateral hemiplegiadue to a dorsal pontine tegmentum lesion affecting the paramedian pontine reticular formation, facial nervenucleus or fascicle, and corticospinal tract
• fracture-dislocation fracture through the articular processes and disc with or without associated fracture through a vertebral body due to flexion/extension with axial loading; unstable and often associated with spinal cord injury
• freezing sudden, brief cessation of movement; common in Parkinson disease
• Fresnel prisms clear, flexible polyvinyl chloride plastic sheets composed of a series of small prisms that are used to assess and correct diplopia
• fried egg artifact perinuclear halo around oligodendrocytes caused by formalin fixation artifact Friedreich’s ataxia autosomal recessive neurodegenerative disease caused by GAA triplet repeat mutation in the gene that encodes for frataxin, a protein that regulates mitochondrial functioning; characterized by weakness, ataxia, sensory loss, scoliosis, and cardiomyopathy
• frontal eye fields (FEF) region within the frontal lobes from which voluntary lateral eye movements originate; with stimulation (as in seizure), the eyes move conjugately to the opposite side; with destruction (as in astroke), the eyes look towards the lesioned side (loss of controversion), implying unopposed stimulation from the undamaged side
• frontotemporal dementia group of dementing illnesses in which disordered behavior (e.g., disinhibition) or language (e.g., aphasia) are disproportionately impaired in relation to memory; includes Pick’s disease andcorticobasal degeneration
• functional not due to organic disease
• gadolinium-enhancing lesion abnormality on MRI that becomes bright after injection of the chemical compound gadolinium; implies breakdown in the blood-brain barrier
• gamma motor neurons neurons that contract the ends of the muscle spindle so that spindle sensitivity to passive stretch is kept constant throughout muscle shortening
• ganglia aggregations of nerve cell bodies gegenhalten see paratonia
• gemistocyte reactive astrocyte having increased glial filaments and glassy eosinophilic cytoplasm
• generalized seizure seizure that affects both cerebral hemispheres simultaneously and causes unconsciousness at the outset
• geniculate ganglion sensory ganglion of the facial nerve that innervates taste buds on the anterior 2/3 of the tongue
• genu kneelike bend in the anterior part of the corpus callosum or internal capsule
• germinal matrix a highly vascular, metabolically active area of the brain located just beneath the ependymallining of the ventricular walls, which is the source of neurons and glial cells that will later migrate to cerebral cortex. It involutes in the second trimester. Germinal matrix vessels are fragile and are believed to have impaired autoregulation, making them prone to rupture in premature infants, resulting in intraventricular hemorrhage.
• Gerstmann syndrome a neurological disorder that includes a writing disability (agraphia or dysgraphia), a lack of understanding of the rules for calculation or arithmetic (acalculia or dyscalculia), an inability to distinguish right from left, and an inability to identify fingers (finger agnosia) that is due to a lesion of the angular gyrus of the dominant parietal lobe
• Glasgow Coma Scale (GCS) most widely used scoring system to quantify level of consciousness following traumatic brain injury; scores range from 3 to 15, based on the sum of the best eye opening response, the best verbal response, and the best motor response

  Eye Opening (E)	Verbal Response (V)	Motor Response (M)
  4=Spontaneous	5=Normal	6=Normal
  3=To voice	4=Disoriented	5=Localizes to pain
  2=To pain	3=Inappropriate	4=Withdraws to pain
  1=None	2=Incomprehensible	3=Flexes to pain
  	1=None	2=Extends to pain
  		1=None
  Total = E+V+M
• glia supporting cells of the nervous system that provide structural and metabolic support for the neurons; includes astrocytes, oligodendrocytes, ependymal cells, and microglia
• glioblastoma multiforme WHO grade IV astrocytoma characterized by hemorrhagic necrosis, endothelial proliferation, ± crossing of the corpus callosum, ring-enhancement on imaging, and poor survival
• gliosis scar or dense fibrous network of glial processes in an area of CNS injury
• global aphasia impairment of language production, comprehension, and repetition due to lesion of entire perisylvian region; usually associated with right hemiparesis
• globus pallidus most medial component of the basal ganglia and generator of most basal ganglionic output
• glossopharyngeal nerve (cranial nerve IX) nerve containing motor, sensory, and parasympathetic fibers; motor fibers originate in the nucleus ambiguus and innervate the stylopharyngeus to elevate the palate; sensory fibers originate in the superior and petrosal ganglion and supply taste to the posterior third of the tongue and tactile sensation to the posterior tongue, pharynx, middle and external ear, and eustacian tube; parasympathetic fibers originate in the inferior salivatory nucleus and carry secretory and vasodilatory fibers to the parotid gland
• Golgi tendon organs sense active stretch and via inhibitory inter-neurons inhibit the motor neurons to provide protection against hurtful contractile forces Gower’s sign maneuver used by patients with proximal muscle weakness (as in myopathy) in order to arise from the floor or from a kneeling or squatting position; the hands are used to “walk up” the thighs
• Gradenigo Syndrome ipsilateral lateral rectus palsy, peripheral facial palsy, decreased hearing, and upper facial pain due to a lesion in the apex of the temporal bone
• grand mal seizure see tonic-clonic seizure
• graphesthesia ability to recognize letters or numbers drawn on the finger or palm
• gray matter part of the CNS consisting of neuronal cell bodies and dendrites
• Guillain-Barre syndrome (acute inflammatory demyelinating polyneuropathy) acute, ascending, and progressive neuropathy believed to result from an autoimmune response triggered by an antecedent illness or various medical conditions and characterized by weakness, paresthesias, hyporeflexia, and labile autonomicdysfunction; most patients exhibit absent or profoundly delayed conduction in nerve fibers resulting fromdemyelination, but in a subset of patients, there is a direct cellular immune attack on the axon itself gustatoryrelating to the sense of taste
• gyrus convoluted ridge on the outer surface of the brain caused by infolding of the cerebral cortex and bound by sulci
• habenula diencephalic structure located on the dorsomedial surface of the caudal thalamus that receivesafferents from the septal nuclei and hypothalamus via the stria medullaris and projects to midbrain nuclei; involved in autonomic processing
• hangman’s fracture fracture through bilateral pedicles of C2 via various mechanisms; typically unstable
• hemianesthesia loss of somatosensation on one half of the body
• hemianopia loss of vision in one half of the visual field, indicating a pathological process posterior to the optic chiasm
• hemiballismus involuntary violent flinging or jerking of a limb (or limbs) in an uncoordinated manner caused by a lesion of the contralateral subthalamus
• hemicrania continua indomethacin-responsive headache disorder characterized by steady, moderately intense unilateral head pain on which are superimposed episodes of more intense pain with autonomicsymptoms (eye tearing, eye redness, eyelid edema, nasal congestion, runny nose) occurring several times a day
• hemifacial spasm segmental myoclonus of muscles innervated by the facial nerve; may be due to vascular compression of the facial nerve or facial nerve injury or tumor, or it may have no apparent cause hemifieldone-half of the binocular visual field
• hemiparesis weakness on one side of the body
• hemiplegia paralysis on one side of the body
• hemiplegic migraine familial form of migraine characterized by temporary (usually < 1 hour but occasionally lasting up to a week) hemiparesis ± hemisensory symptoms often associated with visual aura and headache; in about 50% of affected families, a defect may be found on chromosome 19 or on chromosome 1 and involves abnormal calcium channels
• heterotopia tissue occurring in an abnormal anatomical position hindbrain medulla, pons and cerebellum
• hippocampal formation cortical structure in the medial temporal lobe comprising the dentate gyrus,hippocampus, and subiculum; involved in short-term declarative memory
• hippocampus convoluted structure at the medial margin of the cortical mantle of the cerebral hemisphere, bordering the choroid fissure of the lateral ventricle, and forming part of the limbic system, which is concerned with memory and emotion
• Hoffman’s sign contraction of fingers and thumb when a stimulus is applied to a distal phalanx in that hand; indication of hyperreflexia in the upper extremity
• holoprosencephaly failure of cleavage at the rostral end of the notochord resulting in midline fusion of the frontal lobes, midline facial abnormalities, and often hydrocephalus and heterotopias Homer-Wright rosettehalo of cells surrounding a central lumen containing neuropil; found in medulloblastomas and PNETs
• Horner's syndrome ptosis, miosis, and anhidrosis ipsilateral to damaged sympathetic nerve fibers
• H-reflex electrical equivalent of the monosynaptic stretch reflex elicited by selectively stimulating the Ia fibers of the posterior tibial or median nerve
• Hunt and Hess scale scale for grading clinical status in patients with nontraumatic subarachnoid 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
  coma, decerebrate posturing	5
• Huntington disease fatal autosomal dominant neurodegenerative disorder characterized by chorea and progressive dementia; due to a trinucleotide CAG-repeat mutation on chromosome 4
• hydranencephaly birth defect in which the majority of the cerebral hemispheres and striatum are absent and replaced by sacs filled with cerebrospinal fluid; considered to be an extreme form of porencephaly
• hydrocephalus literally "water on the brain;" increase in size of ventricles and amount of cerebrospinal fluid in the brain
• hyperacusis abnormally increased sensitivity to sound
• hyperpathia exaggerated response to painful stimuli
• hypersomnolence see excessive daytime sleepiness
• hypertensive hemorrhage intraparenchymal hemorrhage with a predilection to occur deep in the cerebral hemispheres, especially in the putamen, thalamus, and deep white matter, as well as the pons and cerebellum. These sites are all supplied by small penetrating arteries that are subject to high sheer stress and have no collaterals, making them vulnerable to the effects of increased blood pressure
• hypertonicity increase in passive muscle resistance, such as spasticity or rigidity
• hypertropia an eye with strabismus that deviates up
• hypnagogic hallucination vivid dreamlike hallucination that occurs as one is falling asleep; one of the symptoms of narcolepsy, but also experienced by some non-narcoleptic individuals
• hypnic headache indomethacin-responsive headache disorder characterized by diffuse, throbbing headache arising exclusively during sleep, typically between 1:00 and 3:00 AM
• hypnic jerk sensation of falling, and then "jerking" awake just as one drifts to sleep
• hypnopompic hallucination vivid dreamlike hallucination that occurs as one is waking up; one of the symptoms of narcolepsy, but also experienced by some non-narcoleptic individuals
• hypoglossal nerve (cranial nerve XII) motor nerve that innervates all tongue muscles except the palatoglossus; lesions result in deviation of the protruded tongue towards the paralyzed side and deviation of the tongue at rest away from the paralyzed side; nucleus is located in the medulla
• hypomimia see facial masking
• hypophysis see pituitary gland
• hypothalamus basal part of the diencephalon that controls hunger, thirst, body temperature, and various metabolic processes, including the maintaining of water balance
• hypotonicity reduction in passive muscle resistance
• hypotropia an eye with strabismus that deviates down
• hypoxia reduction in the supply of oxygen to the brain or other vital organ
• hypsarhythmia abnormal EEG pattern of excessive slow activity and multiple areas of epileptiform activity; associated with infantile spasms
• ice cream headache nickname given to headaches that are cold induced; common in migraine
• ice-pick headache indomethacin-responsive headache disorder characterized by momentary, sharp, and/or jabbing pain that occurs either once or several times a day at irregular intervals
• ictus sudden attack, stroke, or seizure
• idiopathic occurring without known cause; in the context of epilepsy, indicates cases in which no lesion is found and a genetic cause is presumed
• impairment problem in body function or structure such as a significant deviation or loss (e.g., weakness = impairment in the muscles' capability to produce force)
• incisura fissure that separates the uncus from the apex of the temporal lobe
• incyclotorsion (a.k.a. intorsion): cyclotorsion of an eye such that the superior pole rotates inward
• indomethacin-responsive headache class of primary headache disorders characterized by a prompt and often complete response to indomethacin to the exclusion of other nonsteroidal anti-inflammatory drugs and medications usually effective in treating other primary headache disorders; includes ice-pick headache, chronic paroxysmal hemicrania, hemicrania continua, cough headache, and hypnic headache, among others
• infantile spasms form of cryptogenic generalized epilepsy characterized by sudden, forceful forward flexion of the trunk and extension of the arms
• infarction permanent tissue damage and death of all cellular elements (neurons, glia, vessels) due to prolonged or severe ischemia
• inferior cerebellar peduncle (restiform body) paired bundle of fibers traveling to and from the cerebellum;afferent fibers from the dorsal spinocerebellar tract carry proprioceptive information from the upper body;efferent fibers travel to the vestibular nuclei in the dorsal brainstem
• inferior colliculus paired structures on the dorsal surface of the caudal midbrain overlying the cerebral aqueduct that process and relay auditory signals from brainstem centers to the medial geniculate nucleus of thethalamus; with the superior collicui, make up the tectum and the quadrigeminal bodies
• inferior olivary nucleus prominent nucleus in the ventral medulla located just lateral and dorsal to the medullary pyramids; source of climbing fibers that provide a critical input to the cerebellum involved in Purkinje cell plasticity and motor learning
• infratentorial below the tentorium cerebelli, i.e., brainstem and cerebellum
• infundibulum connection between the hypothalamus and the pituitary gland (also called the "pituitary stalk"); contains the hypophyseal portal veins and the axons of hypothalamic neurons that project to the posteriorpituitary
• insomnia difficulty with falling asleep or staying asleep
• insula cerebral cortex lying in the depths of the Sylvian fissure and involved in gustatory, visceral sensory, and emotional processing
• intention tremor tremor whose amplitude increases as the affected body part (typically a finger) nears an intended target and that may the targeted object to be missed; typically results from damage to the cerebellumor its connections
• internal capsule broad compact band of efferent and afferent fibers that travel to or from the cerebral cortex; flanked medially by the thalamus and caudate and laterally by the lentiform nucleus
• internal carotid artery artery that arises from the common carotid artery at the upper border of the thyroid cartilage and terminates in the middle cranial fossa by dividing into the anterior cerebral artery and the middle cerebral artery; constitutes the anterior circulation of the brain
• inter-neuron neurons that receives input from one neurons and projects to another neurons within spinal cord, allowing a greater degree of complexity of movement control
• internuclear ophthalmoplegia failure of adduction of one eye and abducting nystagmus of the other eye due to a lesion of the medial longitudinal fasciculus
• intracranial pressure pressure exerted by the brain, cerebrospinal fluid, and the cerebral blood supply on the intracranial space; measured in centimeters of water (cmH2O) or millimeters of mercury (mmHg); normally < 20 mm/Hg
• intrathecal space (subarachnoid space) space surrounding the brain and spinal cord that containscerebrospinal fluid intraventricular hemorrhage (IVH) bleeding in the ventricles especially from fragile blood vessels in premature infants; in adults may accompany intracerebral or subarachnoid hemorrhage
• ipsilateral located on the same side of the body (brain)
• ischemia impairment of tissue function due to a reduction in blood supply relative to metabolic demand
• ischemic penumbra see penumbra
• Jacksonian march contiguous spread of electrical discharges through superficial cortex occurring with someseizures manifested by spread of muscular jerks to contiguous anatomical areas, such as when the jerking begins in the thumb and then spreads stepwise to the fingers, wrist, forearm, proximal arm, shoulder, and faceJC virus member of the papovavirus family that produces progressive multifocal leukoencephalopathy; “JC” stands for the initials of the first patient described with the virus
• Jefferson fracture burst fracture of the anterior and posterior arches of C1 due to axial loading; typically stable
• jitter measure of the variability of potentials of two muscle fibers innervated by an individual axon as measured by single fiber electromyography; increased in myasthenia gravis
• juvenile myoclonic epilepsy (JME) primary generalized epilepsy syndrome usually beginning between ages 5 to 17 years, characterized by myoclonic (muscle-jerk), absence, and tonic-clonic seizures
• Kernig’s sign pain in the posterior aspect of the thigh in response to passive flexion of the thigh and extension of the knee; indicative of meningeal irritation
• Kernohan’s notch compression of the opposite cerebral peduncle against the edge of the tentoriumcontralateral to a herniating uncus; results in ipsilateral hemiparesis
• ketogenic diet high-fat, low-carbohydrate diet sometimes used to control seizures
• kindling process by which repeatedly applying subconvulsive stimulation either electrically or chemically permanently lowers the threshold for having seizures; used as an experimental model for epilepsy
• Korsakoff syndrome chronic phase of thiamine deficiency characterized by impairment in establishing new memories and retrieving previous memories, occurring most commonly in alcoholics
  Krabbe disease (globoid cell leukodystrophy) autosomal recessive disease arising in infancy with progressive motor and mental retardation and peripheral nerve dysfunction due to a deficiency in the enzyme galactocerebrosidase, which is necessary to degrade galactocerebroside, a myelin constituent
• kuru fatal prion disease restricted to the Fore tribe in the highlands of New Guinea as a result of cannibalistic funeral practices; form of spongiform encephalopathy
• lacune (lacunar stroke) small (<2 cm) infarct, caused by occlusion of a single penetrating branch of a larger cerebral artery
• Lambert-Eaton Myasthenic syndrome autoimmune disorder of neuromuscular transmission characterized by antibodies directed against the voltage-gated calcium channels on the presynaptic motor nerve terminal leading to impaired release of acetylcholine and causing proximal muscle weakness, hyporeflexia, and autonomic changes (e.g., dry mouth); associated with malignancy (particularly small cell lung cancer) in half to ¾ of affected individuals
  laminar necrosis selective neuronal loss in layers 3 and 5 of the cerebral cortex due to hypoxic-ischemic insult
• lateral medullary syndrome (Wallenberg's syndrome) constellation of symptoms including difficulty swallowing, hoarseness, vertigo, nystagmus, ataxia, loss of pain and temperature sense in the ipsilateral face and contralateral body, and ipsilateral Horner's syndrome in association with an infarct in the lateral medulla; due to occlusion of the vertebral or posterior inferior cerebellar artery
• Lennox-Gastaut syndrome syndrome of mental retardation, generalized epilepsy (with mixed seizures, especially tonic, myoclonic and atypical absence), and a characteristic pattern of slow, generalized spike-and-wave activity on the electroencephalogram
• lentiform nucleus (lenticular nucleus) lens-shaped part of the basal ganglia consisting of the putamen andglobus pallidus
• leptomeninges arachnoid mater and pia mater
• leukodystrophy metabolic demyelinative disease
• Lewy body cytoplasmic, bright red sphere often with a surrounding halo on H&E composed of an amorphous granular core with a radiating filamentous periphery; believed to contain alpha-synucein; seen in Parkinson disease and diffuse Lewy body disease
• Lewy body dementia see diffuse Lewy body disease
• light-near dissociation absent pupillary light response but intact near response (i.e., “accommodate but don’t react”) seen with dorsal midbrain lesions, syphilis, and diabetes
• limbic referring to the system comprising the hippocampus, parahippocampal gyrus, cingulate gyrus, fornix, and multiple subcortical structures including portions of hypothalamus and thalamus; important in memory and emotion
• lipohyalinosis eosinophilic deposits in the connective tissue of the walls of perforating arterioles in the deep portions of the brain due to hypertension; contributes to the development of lacunar infarction andhypertensive hemorrhage
• Lissauer’s tract longitudinal bundle of thin, unmyelinated and poorly myelinated fibers capping the apex of the posterior horn of the spinal gray matter, composed of posterior nerve root fibers and short association fibers that interconnect neighboring segments of the posterior horn
• lissencephaly (agyria) smooth brain (absence of secondary sulci)
• lobe one of four major portions of the cerebral cortex named after the overlying cranial bones: frontal, parietal, temporal, and occipital locked-in state tetraplegia and aphonia with preserved consciousness due tobrainstem (usually pontine) lesion that spares the reticular activating system
• locus ceruleus melatonin-containing nucleus located on the dorsal wall of the upper pons that is one of the main sources of neuroepinepherine in the brain and has widespread projections to other parts of the nervous system; mediates arousal and primes neurons throughout the nervous system to be activated by stimuli
• Loftstrand Crutch type of crutch with an attached holder for the forearm that provides extra support
• long-tract signs signs referable to the corticospinal tract, spinothalamic tract, and dorsal columns/medial lemniscus
• lower motor neuron 2nd order neurons whose cell bodies are located in the brainstem or anterior horn of the spinal cord and that leave the CNS to connect to muscle; lesions result in flaccid weakness, reflex loss, atrophy, +/- fasciculations
• lumbar puncture procedure in which a needle is inserted through the skin between the fourth and fifth lumbar vertebrae and into the lumbar subarachnoid space for measurement of cerebrospinal fluid analysismacrocephaly head circumference that is more than 2 standard deviations above the mean for age, sex, race, and gestation
• macula part of the retina responsible for detailed central vision magnetoencephalography (MEG) noninvasive functional neuroimaging technique used to measure magnetic fields generated by intracellular electrical currents from brain neurons; clinical uses include localization of epileptic discharges and localization ofeloquent cortex or surgical planning
• mammillary bodies pair of nuclei in the posterior, ventral and medial hypothalamus that receive hippocampal inputs via the fornix and project to anterior nucleus of the thalamus and the tegmentum of the midbrain andpons; involved in memory processing
• Marcus-Gunn pupil see afferent pupillary defect
• mass effect structural damage due to a lesion’s bulk (e.g., tumor, infarct, or hemorrhage), the blockage of fluid movement (e.g., compression of a ventricle), or excessive accumulation of fluid
• medial geniculate nucleus nucleus of the posterior, dorsal thalamus that receives auditory input from theinferior colliculus and relays this information to the primary auditory cortex (Brodmann's areas 41 & 42) in the superior temporal gyrus.
• medial lemniscus ascending axonal tract in the brainstem that carries tactile and proprioceptive information from the dorsal column nuclei to the ventral posterior lateral nucleus of the thalamus
• medial longitudinal fasciculus pathway connecting the ipsilateral 3rd nerve nucleus in the midbrain to thecontralateral 6th nerve nucleus in the pons for ocular motor control
• medication overuse headache (analgesic rebound headache) headache disorder characterized by headache that is present on 15 or more days per month in association with the use of any analgesic (including aspirin, acetaminophen, narcotics, ergotamine, and triptans) at least two or three days each week, with intake of the drug on at least 10 days per month for at least three months; headache resolves or reverts to its previous patterns within two months after discontinuation of the drug
• medulla a part of the brainstem that helps regulate respiration and other behaviors
• medulloblastoma aggressive WHO grade IV primitive neuroepithelial tumor of children and young adults typically involving the posterior fossa sometimes with cerebrospinal fluid seeding (drop metastases); characterized histologically by small blue cells and Homer Wright rosettes
• medulla oblongata (myelencephalon) caudal aspect of the brainstem located between the pons and the spinal cord
• megalencephaly abnormally large, heavy, and usually malfunctioning brain; thought to be related to a disturbance in the regulation of cell reproduction or proliferation
• Meissner corpuscles dermal mechanoreceptors that subserve light touch sensation
• MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes) mitochondrial disorder characterized by hearing loss, episodic vomiting, and recurrent cerebral insults resembling strokes and causing hemiparesis, hemianopia, or cortical blindness
•  meningeal carcinomatosis diffuse infiltration of the meninges by metastatic tumor cells often with positivecerebrospinal fluid cytology
• meninges three distinct connective tissue membranes (from outer to inner: dura, arachnoid, and pia mater) that enclose and protect the central nervous system
• meningioma slow-growing WHO grade I meningeal neoplasm that has an extra-axial location and often shows a dural tail sign and hyperostosis of adjacent skull; characterized histologically by whorls and psammoma bodies
• meningitis inflammation of meninges and spinal fluid
• meningocele form of spina bifida in which there is herniation of only meninges (no spinal cord parenchyma) through defective posterior arches meninx singular form of meninges
• menstrual (catamenial) migraine migraine occurring between one day before and four days after the onset of menses; thought to be due to estrogen withdrawal
• Merkel cells disk-shaped receptor endings in the skin believed to be involved with the sensation of fine touch
• mesencephalon see midbrain
• mesial temporal sclerosis hippocampal scarring and volume loss; most common cause of temporal lobe epilepsy
• Mesulam syndrome eponym for primary progressive aphasia
• metachromatic leukodystrophy autosomal recessive disease associated with large confluent areas of discolored gelatinouswhite matter caused by deficiency of the enzyme arylsulfatase A, which is necessary for the degradation of sulfatide, a myelin constituent
• Meyer’s loop part of the optic radiations that fans out into the temporal lobe and carries information from the upper visual world
• microcephaly head circumference that is smaller than normal because the brain has not developed properly or has stopped growing; most often caused by genetic abnormalities
• microglia bone marrow derived phagocytic cells that are involved in immune reactions in the CNS microglial nodules formation of clusters of activated microglia around foci of necrotic brain tissue
• micrographia small, cramped handwriting
• midbrain (mesencephalon) rostral aspect of the brainstem located between the pons and the diencephalon
• middle cerebellar peduncle (brachium pontis) paired bundle of fibers originating from the pontine nuclei,decussating in the base of the pons, and ending in the contralateral cerebellar cortex
• middle cerebral artery branch of the internal carotid artery; supplies blood to the entire lateral aspect of each hemisphere including the lateral motor strip, lateral sensory strip, language areas, putamen, globus pallidus, andinternal capsule
• middle cranial fossa butterfly-shaped portion of the internal base of the skull housing the temporal lobes laterally and the pituitary centrally
• migraine headache attacks lasting 4-72 hours consisting of moderate to severe intensity unilateral, pulsating head pain that is aggravated by routine physical activity, inhibits daily activities, and is associated with nausea/vomiting, photophobia, and phonophobia
• migraine aura focal neurological phenomena (visual, sensory, motor, or language) preceding or accompanying a migraine attack, usually developing over 5-20 minutes and lasting < 1 hour; may occur in isolation or before (most commonly), during, or after the onset of headache
• migraine with aura (classic migraine) migraine attack associated with reversible aura symptoms indicative of focal CNS dysfunction; the aura (scintillating scotoma, vertigo, paresthesias, paresis, etc) typically develops gradually over several minutes, lasts less than 60 minutes, and occurs before, during, or after headache
• migraine without aura (common migraine) migraine attack without associated neurological deficits
• mild cognitive impairment (MCI) cognitive changes intermediate between normal aging and clinically diagnosed Alzheimer disease; identifies individuals believed to be at risk for Alzheimer disease
• Millard-Gubler syndrome ipsilateral lateral rectus palsy, ipsilateral peripheral facial palsy, and contralateralhemiplegia due to a ventral pontine lesion affecting the abducens and facial nerve fascicles and corticospinal tract
• miosis pupillary constriction
• mitochondrial myopathies neuromuscular diseases caused by damage to the mitochondria (small, energy-producing structures found in every cell in the body )
• Mollaret meningitis benign recurrent aseptic meningitis mononeuropathy multiplex (mononeuritis multiplex) condition associated with various systemic disorders (e.g., diabetes, polyarteritis nodosa) characterized by isolated damage to two or more nerves; a multifocal peripheral neuropathy
Monroe-Kellie doctrine doctrine stating that the total cranial volume tends to remain constant. An increase in the volume of any of its three components (brain, blood, or CSF) or the addition of a space-occupying lesion (e.g., tumor) occurs at the expense of the volume of the other components; once the components have redistributed as much as they can, any further increase in volume results in increased intracranial pressure
• Moro reflex normal neonatal reflex consisting of symmetric abduction followed by adduction of both arms, elicited by gently allowing the back of the head to drop; present during the first 4-6 months of life
• motor neglect inability to look or reach toward left-sided objects
• Motor neurons nerve cells that direct movement motor neuron disease dysfunction of alpha motor neurons; motor neuronopathy
• motor unit motor neuron axon and the individual muscle fibers it branches to contact
• moyamoya syndrome usually bilateral, progressive occlusive disease of the large cerebral arteries leading to the development of an abnormal collateral vascular network adjacent to the stenotic vessels; manifest most commonly by infarcts in children and hemorrhages in adults
Muller’s muscle eyelid muscle innervated by the sympathetic nervous system and that functions to elevate the upper eyelid; interruption of these sympathetic fibers results in the ptosis that is part of Horner's syndrome.
• multi-infarct dementia form of vascular dementia involving deterioration of mental function caused byinfarcts in multiple brain regions
• multiple sclerosis inflammatory demeyelating disease with relative axonal sparing of the central nervous system usually characterized by recurrent attacks of focal and multifocal neurological disability
•