- multiple sleep latency test (MSLT) standard test used to quantify the overall daytime sleep tendency by measuring the speed of falling asleep (sleep latency) usually in 5 tests carried out at two-hour intervals
- multisystems atrophy (MSA) collective term for a group of Parkinson plus syndromes involving various degrees of parkinsonism, autonomic failure, cerebellar dysfunction, and, pyramidal signs that are poorly responsive to levodopa or dopamine agonists; pathologic hallmarks are glial cytoplasmic inclusions and aneuronal multisystem degeneration; replaces the older designations Shy-Drager syndrome, striatonigral degeneration, and olivopontocerebellar atrophy
- muscle spindle stretch receptor in vertebrate muscle that is innervated by both sensory and motor neuronsaxons and sends proprioceptive information about the muscle to the central nervous system
- mutism inability to produce any verbal utterance; may be due to disordered language, speech, or voice
- myasthenia gravis disease of the neuromuscular junction in which an antibody-mediated attack on nicotinic acetylcholine receptors impairs neuromuscular transmission, resulting in fluctuating, fatigable weakness that responds to cholinergic drugs
- mycotic aneurysm infective aneurysm typically developing distal to the Circle of Willis and reflecting local bacterial or fungal intramural growth with rupture of the vascular wall
- mydriasis pupillary dilation
- myelencephalon see medulla
- myelin fatty substance forming an insulating sheath around axons to increase the velocity of action potential conduction; produced by oligodendrocytes in the CNS and by Schwann cells in the PNS
- myelitis inflammatory disease of the spinal cord
- myelogram diagnostic procedure in which contrast material is injected into the spinal subarachnoid spaceallowing visualization of the spinal cord and nerve roots
- myelomeningocele form of spina bifida in which there is herniation of meninges and spinal cord parenchymathrough defective posterior arches
- myokymia involuntary repetitive contractions of muscle fibers lasting a few seconds and giving a continuous rippling or undulating appearance to the overlying skin; associated with nerve irritation
- myopathy muscle disease; manifested by lower motor neurons weakness that is usually proximal>distal
- (cataplexy, sleep paralysis, hypnagogic hallucinations, and an abnormal tendency to pass directly into REM sleep from wakefulness)
- near reflex triad convergence, accommodation, and pupilloconstriction evoked by targets that move close to you
- negative symptom reduction (weakness, numbness) or complete loss (paralysis, analgesia) of function; implies at least partial or complete failure of impulse conduction in a functional system
- neglect failure to acknowledge stimuli toward the side of space opposite to a hemispheric (usually parietal) lesion
- Negri body viral inclusion in hippocampal, neocortical, or Purkinje cell neurons that is the diagnostic hallmark of rabies encephalitis
- neologism made-up word
- nerve conduction velocity study method of diagnosing the type and location of nerve injury using application of electrical stimulation to the nerve
- network inhibition hypothesis proposed pathophysiological mechanism for complex behavioral phenomena and impaired consciousness in complex partial seizures; theory is that the seizures induce excitation in the temporal lobe that propagates to the dorsomedial thalamus and upper brainstem reticular formation, disrupting the normal activating functions of these areas, and resulting in widespread functional depression of bilateral frontal and parietal association cortex neuralgia pain that follows the paths of specific nerves, e.g., trigeminal neuralgia; postherpetic neuralgia neural plate ectodermal tissue on the dorsal surface of the embryo that forms the neural tube, which develops into the central nervous system neural tubeembryonic brain and spinal cord neural tube defect malformation of the brain and/or spinal cord in embryo; classified based on location, extent, and the presence or absence of exposed neural tissue (open or closed)
- neuraxis often used synonymously with central nervous system (even though some suggest that it represents only the unpaired portions of the CNS)
- neuritic plaque mature plaque composed of a) silver-positive swollen neurites engorged with aggregates of paired helical filaments and round dense bodies and b) an amyloid core; seen in Alzheimer's disease
- neurofibrillary tangles flame-shaped intracytoplasmic inclusions in cortical neurons consisting of paired helical filaments; characteristic of, but not unique to, Alzheimer's disease
- neurogenic bladder bladder dysfunction associated with a lesion in the brain, spinal cord, or peripheral nerves and characterized by underactivity (failure to empty) or overactivity (failure to store); symptoms include urinary urgency, frequency, hesitancy, nocturia, and incontinence
- neuroglia see glia
- neuroleptic drug that blocks dopamine receptors; antipsychotic drug
- neuroleptic malignant syndrome rare, but life-threatening, idiosyncratic reaction to antipsychotic drugs that is characterized by high fever, hypertension, severe rigidity, altered mental status, and autonomic dysfunction; may occur with either severe blockade (high doses of neuroleptics) or sudden depletion (withdrawal of neuroleptics) of dopamine receptors neurologist a physician who specializes in the diagnosis and treatment of disease of the nervous system
- neurology medical specialty dealing with the nervous system and the diseases affecting it
- neuromuscular junction junction (synapse) between the terminal of a motor neurons and a muscle fiber; myoneural junction
- neuronopathy dysfunction and reflex loss due to disease of cell bodies (sensory=dorsal root ganglion; motor=alpha motor neurons, more commonly called motor neuron disease)
- neuropil unmyelinated neuronal processes (axons and dendrites) in the gray matter of the central nervous system neuroprotection strategies that ameliorate the biochemical and metabolic derangements induced by cerebral ischemia, thus limiting delayed neuronal injury neurotransmitter chemical substance that transmits electrical impulses between neurons neurulation process by which the neural tube is formed; consists of folding of the neural plate on the dorsal side of the embryo (resulting in the formation of the brain and spinal cord) followed by canalization (resulting in the development of the caudal spinal cord)
- nightmare unpleasant and/or frightening dream that usually awakens a person from REM sleep; affected individual usually remembers the event, unlike in night terror
- night terror (sleep terror; pavor nocturnes) sleep disorder (usually of children) involving abrupt awakening from sleep in a terrified state that represents incomplete arousal from nonREM sleep; affected individual is usually confused and does not remember details of the event, unlike in nightmare
- nociceptive painfulnodulus posterior part of the cerebellar vermis; medial portion of the vestibulocerebellum
- non-communicating hydrocephalus blockage of CSF flow along one or more of the narrow pathways connecting the ventricles (most commonly the cerebral aqueduct)
- non-fluent aphasia (Broca’s or expressive aphasia) selective impairment of language production including impaired repetition due to a lesion of the left inferior frontal lobe (Brodmann areas 44 and 45)
- normal pressure hydrocephalus (NPH) clinical symptom complex characterized by abnormal gait, urinary incontinence, and dementia in the setting of hydrocephalus with normal cerebrospinal fluid pressure; proposed pathophysiology is that there is diminished cerebrospinal fluid absorption at the arachnoid villi, which leads to transient high-pressure hydrocephalus with subsequent ventricular enlargement and return of cerebrospinal fluid pressure to normal
- Nothnagel Syndrome ipsilateral oculomotor palsy and contralateral ataxia due to a midbrain tegmental lesion affecting the III nerve fascicle and superior cerebellar peduncle
- notochord embryological predecessor of the vertebral column nuchal rigidity stiff neck
- nucleus collection of neuronal cell bodies
- nucleus ambiguus motor nucleus in the dorsolateral medulla that innervates striated muscle in the neck and thorax
- nucleus cuneatus nucleus located in the lower medulla containing the second-order sensory neurons that relay mechanosensory information from peripheral receptors in the upper body to the thalamus via the medial lemniscus
- nucleus gracilis nucleus located in the lower medulla containing the second-order sensory neurons that relay mechanosensory information from peripheral receptors in the lower body to the thalamus via the medial lemniscus
- nystagmus involuntary, rhythmic oscillation or trembling of the eyeballs
- obtundation mild to moderate reduction in alertness with slow response to stimulation, decreased interest in environment, and increased number of hours of sleep
- ocular migraine form of migraine characterized by monocular visual loss typically followed by an ipsilateralperiorbital (or less commonly diffuse) headache
- oculocephalic response (OCR/Doll’s phenomenon) reflex eye movements assessed in an uncooperative or unresponsive patient to determine whether brainstem extraocular pathways are intact; performed by quickly turning the head, stimulating proprioceptive afferents from the neck and/or the vestibular system; considered positive (brainstem pathways intact) if head turn produces conjugate eye deviation in the opposite direction; absent response implies that either brainstem pathways are impaired or the patient is too awake to assess
- oculogyric crisis acute dystonic reaction to neuroleptic drugs manifested by sudden sustained twisting of the head and upward deviation of the eyes; responsive to anticholinergic or antihistamine medications
- oculomotor nerve (cranial nerve III) motor nerve innervating the superior, inferior, and medial recti, inferior oblique, and levator palpebrae superioris muscles and providing preganglionic parasympathetic fibers to the ciliary ganglion to control pupillary constriction; III palsy causes down and out eye deviation, ptosis, and a dilated unreactive pupil (pupillary fibers on the outside so spared with intrinsic lesion); lesions of the nucleus, located in the medial midbrain, typically cause weakness of all muscles innervated by the ipsilateral III nerve, contralateralsuperior rectus weakness, and bilateral incomplete ptosis;
- oculovestibular response (OVR/cold calorics/vestibulo-ocular response/VOR) reflex eye movements that keep vision stable upon head rotation and involve connections between the ipsilateral 8th and 3rd and thecontralateral 6th nerve nuclei; horizontal movements are tested by instilling ice water into one ear, stimulating the lateral semicircular canal; in a normal awake patient, the eyes will slowly deviate towards the irrigated ear and then beat quickly away from the irrigated ear as the supratentorial frontal eye fields try to re-fix vision
- odontoid fracture fracture through the odontoid process of C2 due to horizontal shearing and axial loading; type I usually stable and type II usually unstable
- olfactory nerve (cranial nerve I) sensory nerve mediating smell
- oligemia reduction in blood flow associated with an increase in oxygen extraction fraction but maintenance of normal metabolism
- oligoclonal bands two to five bands of immunoglobulins on protein electrophoresis of cerebrospinal fluidseen in multiple sclerosis and other central nervous system disorders
- oligodendroglioma WHO grade II primary CNS tumor typically involving the cerebral hemispheres; characterized histologically by uniform round nuclei with a perinuclear halo (fried egg artifact) and perineuronal satellitosis
- olivopontocerebellar atrophy (OPCA) older term for a variant of multisystems atrophy characterized by preferential degeneration of the cerebellum and brainstem producing symmetric parkinsonism and ataxia,dysarthria, dysphagia, pyramidal signs, and often ocular motility disorders
- Ondine's curse (central alveolar hypoventilation) condition in which the respiratory center in the brain is unable to stimulate breathing in response to an increased amount of carbon dioxide in the blood; typically worsens during sleep
- one-and-a-half syndrome combination of an abducens nerve nuclear lesion and an ipsilateral medial longitudinal fasciculus lesion resulting in an ipsilateral gaze paralysis and loss of adduction of the ipsilateral eye
- on-off phenomenon sudden, unpredictable changes in motor performance by patients on levodopa therapy
- opening pressure cerebrospinal fluid pressure obtained upon entering the subarachnoid space by spinal puncture
- ophthalmoplegia paralysis or weakness of one or more of the muscles that control eye movement
- opisthotonos abnormal posturing of the body with severe arching of the back and the head thrown backwards; may occur with meningeal irritation, especially in infants, or with depressed brain function
- optic atrophy wasting of the optic disc that results from partial or complete degeneration of optic nerve fibers and is associated with a loss of visual acuity
- optic chiasm partial crossing of about half the axons in each optic nerve to enter the contralateral optic tract; lesion results in loss of vision in the temporal hemifield of both eyes
- optic nerve extent of the visual system pathway from the retina to the optic chiasm; contains axons of ganglion cells in the retina of the ipsilateral eye; lesion results in loss of vision in one eye
- optic neuritis inflammation or demyelination of the optic nerve with transient or permanent loss of vision +/- pain
- optic tract extent of the visual system pathway from the optic chiasm to the lateral geniculate nucleus of thethalamus; contains axons from ganglion cells in the retinas of both the left and right eyes, but information from only one half (either left or right) of each eye's visual field; lesion results in loss of vision in contralateralhemifield of both eyes
- orthotic mechanical appliance such as a leg brace or splint that is designed to control, correct, or compensate for impaired limb function
- osmophobia enhanced sensitivity to odors
- oxycephaly premature fusion of all cranial sutures producing an elongated head
- oxygen extraction fraction the fraction of available oxygen extracted by the brain from the blood
- palsy paralysis of a muscle group
- papilledema swelling of nerve head usually but not always due to increased ICP
- parachute reflex protective reflex of normal infants (present by 7-9 months) in which both arms go out in front in response to the head being held down and pointed toward the floor
- paramedian pontine reticular formation (PPRF) collection of premotor neurons located in or near the abducens nucleus that drive horizontal gaze when excited by the cerebral cortex
- parameningeal adjacent to the meninges; includes nasal cavity, middle ear, paranasal sinuses, mastoid, infratemporal fossa, and pterygopalatine fossa
- paraphasia speech error characterized by substitutions of letters (e.g., "bree" for "tree") or words (e.g., "house" for "tree")
- paraplegia paralysis of both legs
- parasagittal sagittal section that is lateral to the midline
- parasomnia disorder in which abnormal behavior intrudes into the sleep process; includes somnambulism,night terrors, and bruxism
- parasympathetic nervous system part of the autonomic nervous system concerned with conservation and restoration of energy; its preganglionic fibers arise from the motor nuclei of cranial nerves III, VII, IX and X in thebrainstem and from the second, third and fourth sacral segments of the spinal cord paratonia (gegenhalten)increased muscle tone that increases in proportion to the speed and strength with which the examiner tries to move the joint; indicative of extensive bihemispheric or bifrontal dysfunction
- paresis reduced ability to activate motor neurons; weakness
- Parinaud’s syndrome (dorsal midbrain syndrome) syndrome characterized by a supranuclear palsy of vertical conjugate movements, convergence-retraction nystagmus, and light-near dissociation of the pupillary reflex; eyes may be forced downward; due to lesion of the dorsal midbrain including pressure on the it fromhydrocephalus or increased intracranial pressure
- Parkinson disease neurodegenerative disease characterized by initially asymmetric resting tremor,bradykinesia/akinesia, rigidity, and postural instability due to loss of cells in the substantia nigra with striatal dopamine deficiency and residual Lewy bodies
- parkinsonism complex of symptoms including resting tremor, bradykinesia/akinesia, rigidity, and postural instability that are due to striatal dopamine deficiency or reduced function; may be seen in a variety of neurodegenerative disorders including idiopathic Parkinson disease, Lewy body dementia, corticobasal degeneration, progressive supranuclear palsy, multisystems atrophy
- Parkinson plus syndromes primary neurodegenerative disorders associated with complex clinical presentations including parkinsonism that reflect degeneration in various neuronal systems in addition to thesubstantia nigra; parkinsonian features are characterized by symmetry of signs, truncal>appendicular signs, and lack of response to levodopa or dopamine agonists
- participation restrictions problems an individual may experience in their own involvement in life situations (e.g., inability to return to work).
- penumbra area surrounding the dense core of irreversibly damaged cells that has preserved ionic homeostasis and reduced neuronal electrical activity but that is capable of recovery
- perceptual neglect inability to distribute spatial attention to objects in the visual field
- periaqueductal gray tegmental gray matter surrounding the cerebral aqueduct within the midbrain that is important in the processing of pain
- perineurium connective tissue sheath surrounding a bundle of nerve fibers
- periodic limb movement disorder sleep disorder characterized by repetitive stereotyped movements during sleep, most commonly an extension of the big toe and dorsiflexion of the ankle; often associated with a partial arousal or awakening of which the patient is typically unaware
- peripheral nervous system nerve cell body, spinal nerve root, plexus, peripheral nerve, neuromuscular junction, and muscle
- perisylvian plexus referring to structures around the Sylvian fissure; includes Wernicke's area in auditory association cortex and Broca's area in front of motor cortex
- perimysium connective tissue sheath surrounding a bundle of muscle fibers
- petit mal seizure see absence seizure
- phonophobia abnormal intolerance to sound that commonly occurs in migraine and other headaches
- physiologic tremor subtle low amplitude, high frequency tremor most easily observed in the hands that is present in healthy persons and most prominent during posture and action
- pia innermost layer of the meninges that is intimately applied to the surface of the brain parenchyma and spinal cord and separated from the arachnoid by the subarachnoid space
- Pick’s disease form of frontotemporal dementia characterized by a slowly progressive deterioration of social skills and changes in personality in addition to impairment of intellect, memory, and language; defined pathologically by Pick bodies (rounded tau-posiotive inclusions similar to neurofibrillary tangles) and Pick cells (swollen or ballooned neurons) in a predominantly frontal location
- pincer grasp finger-thumb opposition
- pineal midline body attached to the posterior part of the third ventricle and lying between the superior colliculi, below the splenium of the corpus callosum; major site of melatonin biosynthesis
- pituitary apoplexy spontaneous hemorrhagic infarction of a typically large and nonfunctioning pituitaryadenoma presenting with headache, nausea and vomiting, cranial nerve II, III, IV, or VI palsies, altered mental status, and hypopituitarism
- pituitary gland (hypophysis) endocrine organ lying ventral to the hypothalamus and optic chiasm; includes an anterior glandular lobe made up of hormone-secreting cells and a posterior neural lobe containing the terminals of neuropeptide-secreting, hypothalamic neurons
- placing (stepping) response normal neonatal reflex consisting of elevating the foot and moving it forward when its dorsal surface is touched; the infant will appear to attempt to stand or walk
- plagiocephaly premature fusion of a unilateral coronal and/or lambdoid +/- sagittal suture
- plantar response superficial (cutaneous) reflex elicited by applying a stimulus to the skin of the foot or leg; flexion (curling down) of all toes (“downgoing toe”) is a normal response, while extension of the great toe (“upgoing toe”) with fanning of the other toes is abnormal and signifies a lesion of the corticospinal tract. Many methods of eliciting the plantar reflex have been described, including the following:EponymTechnique
Babinski Stimulation of the plantar surface of the foot with a blunt point from the heel forward, crossing the metatarsal pad from the small to the great toe Chaddock Stimulation of the lateral aspect of the foot with a blunt point from the heel forward to the small toe Oppenheim Application of heavy pressure with the thumb and index finger to the anterior surface of the tibia with downward stroking from the infrapatellar region to the ankle Gordon Squeezing or applying deep pressure to the calf muscles Strümpell Forceful pressure on the anterior tibia Moniz Forceful passive plantar flexion of the ankle Gonda-Allen Downward snapping of the distal phalanx of the second or fourth toe Stransky Gentle extension of the small toe laterally Bing Application of pinprick to the dorsal surface of the great toe - polysomnogram continuous and simultaneous recording of multiple physiological variables during sleep
- porencephaly cerebral hemispheric cyst that is usually the remnant of a destructive lesion (e.g., stroke or infection) or is due to abnormal brain development
- positive sharp wave spontaneous muscle activity seen on electromyography in association with denervation or irritable myopathy consisting of long action potentials with initial positive (down) wave followed by wide negative (up) wave
- positive symptom exaggeration of a physiological phenomenon; implies abnormal excessive (irritative”) discharges in gray matter or (e.g., seizure or hemifacial spasm) or chronic imbalance in complex integrated motor pathways (e.g., chorea)
- postdrome period following a migraine during which a person has impaired concentration, fatigue, or irritability
- posterior cerebral artery paired arteries that arise from the top of the basilar artery; supply blood to the posterior areas of the brain, including the medial occipital lobes (visual cortex), the inferior temporal lobes, andthalamus
- posterior commissure one of the three major groups of commissural fibers that crosses the midline of the epithalamus just dorsal to the point where the cerebral aqueduct opens into the third ventricle
- posterior communicating artery branch of the internal carotid artery that joins the middle cerebral artery(anterior circulation) to the posterior cerebral artery (posterior circulation); supplies thalamus, hypothalamus,optic chiasm, and mammillary bodies
- posterior cord syndrome spinal cord injury syndrome associated with damage to the posterior portion of the spinal cord resulting in bilateral loss of vibration /proprioception +/- bilateral weakness below the level of the lesion
- posterior horn (dorsal horn) gray matter in the back of the spinal cord that receives sensory information from the body through the dorsal root ganglia post-herpetic neuralgia condition following an acute varicella zoster infection (shingles) characterized by persistent pain (3 or more months) in the dermatomal distribution of the previous zoster rash
- postural instability loss of ability to make postural adjustments in response to perturbations, i.e., defect in righting reflex; common in Parkinson disease
- postural tremor tremor that occurs with the maintenance of a posture or position against gravity
- posture ability to stand upright automatically against gravity; controlled by the vestibulospinal, reticulospinal, and tectospinal pathways
- praxis ability to plan, time, sequence, and spatially organize skilled movements prefrontal cortex corticalregion of the frontal lobe lying anterior to primary and premotor cortex; mediates various executive functions, with the dorsolateral division involved in working memory processes, planning, and decision making, and the ventromedial division involved in emotion and the organization of appropriate social behavior
- primary progressive clinical course of multiple sclerosis characterized from the beginning by progressive disease, with no plateaus or remissions, or an occasional plateau and very short-lived, minor improvements
- primary progressive aphasia progressive form of dementia characterized by global loss of language abilities and initial preservation of other cognitive functions; pathologically, there may be spongiform changes in teh frontal and temporal lobes rather than Alzheimer-like changes primitive neuroepithelial tumor (PNET)tumor histologically similar to the medulloblastoma but located outside the posterior fossa
- prion proteinacious infectious agent responsible for various fatal brain diseases classified as spongiform encephalopathy
- prodrome premonitory phenomena occurring hours to days before headache onset in migraine consisting of psychological, neurological, or constitutional symptoms
- progressive multifocal leukoencephalopathy (PML) fatal demyelinating CNS disease of immunocompromised patients caused by reactivation of the JC papovavirus
- progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome) Parkinson plus syndromecharacterized by predominantly axial rigidity, akinesia, supranuclear ophthalmoplegia (impairment of voluntary vertical gaze—downward more than upward), and pseudobulbar palsy
- prosencephalon see forebrain
- prosody emotional content of language pseudoathetosis involuntary slow, writhing movements of a limb (usually the hand or fingers) occurring when the eyes are closed due to impaired proprioception. Unlike inathetosis, the movements are not present when the eyes are open because visual feedback provides the necessary information to know where the limb is in space.
- pseudobulbar affect condition in which episodes of laughing and/or crying occur with no apparent precipitating event
- pseudobulbar palsy syndrome characterized by dysarthria, dysphagia, dysphonia, impairment of voluntary movements of tongue and facial muscles, and emotional lability; caused by diseases such as multiple sclerosis, motor neuron disease, and stroke that affect the motor fibers traveling from the cerebral cortex to the lowerbrainstem (i.e., corticobulbar tracts)
- pseudorosette spoke-wheel arrangement of cells with tapered cellular processes surrounding a blood vessel, creating a perivascular nuclear free zone; seen in most ependymomas and less commonly in other CNS tumorsptosis eyelid droopiness
- pupillary light response contraction of the pupil on exposure of the retina to light; dependent on proper functioning of the optic and oculomotor nerves
- putamen largest and most lateral component of the basal ganglia
- pyramid prominent column of white matter on the ventromedial margin of the medulla containing axons of the corticospinal tract
- pyramidal tract see corticospinal tract
- quadrantanopia loss of vision in either the upper or lower aspect of one hemifield (involving both eyes)
- quadrigeminal bodies two pairs of elevations on the dorsal surface of the midbrain; includes the superior colliculi and inferior colliculi
- quadriplegia (tetraplegia) paralysis of all four extremities rachischisis fissure of the spinal cord resulting in exposure of the incompletely folded cord along the back
- Ramsy-Hunt syndrome facial paralysis, hyperacusis, loss of taste, and vesicles on the eardrum, external auditory meatus, or palate due to herpes zoster infection of the geniculate ganglion
- raphe ridge of tissue
- Raymond syndrome ipsilateral lateral rectus palsy and contralateral hemiplegia sparing the face due to aventral pontinelesion affecting the abducens nerve fascicles and corticospinal tract (but sparing the facial nerve)
- recurrent-remittent episodic attacks of symptoms with rapid recovery to normal health; implies repeating episodes of a single process (e.g., transient ischemic attacks (TIA), seizures, migraine, and multiple sclerosis)
- red desaturation finding of dimmer perception of the color red in an eye affected by optic nerve disease such as optic neuritis; sign of subtle asymmetry in optic nerve function since color desaturation may occur despite normal visual acuity
- red nucleus oval nucleus centrally placed in the upper midbrain reticular formation that receives fibers from the deep cerebellar nuclei and cerebral cortex and projects to the cerebellum, brainstem, spinal cord, and probably thalamus
- relapsing-remitting clinical course of multiple sclerosis characterized by episodic attacks of symptoms with recovery to normal health
- REM behavior disorder disorder occurring during REM sleep in which the normal motor atonia is partially or completely absent such that dreams can be acted out with punching, kicking, and jumping out of bed
- REM sleep (rapid eye movement sleep) sleep stage in which vivid dreaming occurs; identified by the occurrence of rapid eye movements under closed eyelids, motor atonia, low voltage EEG pattern, bursts of muscular twitching, irregular breathing, irregular heart rate, and increased autonomic activity.
- restiform body see inferior cerebellar peduncle
- resting tremor medium-frequency (3-6 Hz) tremor that occurs maximally with the affected body at rest rather than with holding a sustained posture or making an intentional movement; common in Parkinson disease
- restless legs syndrome sleep disorder characterized by tingling, creepy-crawly, or aching sensation in the legs and sometimes arms as well as motor restlessness that tends to occur at rest (especially around the patient’s usual bedtime) and to be relieved temporarily by movement
- reticular activating system (RAS) the activating mechanisms that lie in or near the central gray matter of thediencephalon, midbrain, and rostral pons and are responsible for mediating consciousness
- reticular formation heterogeneous collection of neurons scattered throughout the brainstem tegmentumthat either modulate forebrain and spinal cord activity or coordinate the firing patterns of lower motor neuronsengaged in reflexive or stereotypical somatic motor and visceral motor activities
- retina light-sensitive neuronal layer lining the back of the eye that sends impulses through the optic nerve that are translated into a visual image; part of the central nervous system retropulsion a tendency to walk backward involuntarily that can occur in Parkinson disease
- righting reflex ability to make postural adjustments in response to perturbations
- rigidity increased resistance throughout the range of motion when passively moving a body part due to co-contraction of agonist and antagonist muscles ("lead pipe")
- ring-enhancement CT or MRI contrast enhancement surrounding a lesion that has blood-brain barrierbreakdown, such as metastatic tumor or abscess
- Romberg test inability to maintain upright posture when feet together and eyes closed; indicates impairedproprioception
- rooting reflex normal neonatal reflex consisting of turning the head towards a stimulus presented to the side of the mouth, latching on, and sucking
- Rosenthal fibers eosinophilic corkscrew or rod-shaped inclusions seen in pilocytic astrocytoma rostral toward the head or nose
- rostrocaudal literally “from the nose to the tail”; used to describe the sequence of symptoms referable to progressively lower parts of the brainstem characteristic of transtentorial herniation
- rubral tremor low-frequency (<4.5 Hz) tremor often of irregular, coarse rhythm that is present during both rest and intentional movements and typically follows cerebellar outflow pathway lesions
- Ruffini corpuscles thermoreceptors in the skin
- saccade discrete, rapid conjugate eye movements from one object to another
- saccular aneurysm spherical outpouching from one side of an artery that occurs at an arterial bifurcation point and reflects weakness of all layers of the vessel wall
- sagittal vertical plane passing through the standing body from front to back sagittal sulcus (longitudinal fissure) long, deep, sagittally oriented cleft that separates the two cerebral hemispheres on the dorsal midline
- scanning speech (ataxic dysarthria) abnormal staccato-like speech due to a lesion of the cerebellum orcerebellar pathways
- scaphocephaly (dolichocephaly) premature closure of the sagittal suture
- schizencephaly developmental birth defect characterized by abnormal slits or clefts in the cerebral hemispheres extending from the cortical surface to the underlying ventricle
- schwannoma WHO grade I benign peripheral nerve sheath tumor occurring commonly in thecerebellopontine angle (cranial nerve VII) or in the bony foramina around the spinal cord (spinal nerve root); characterized histologically by Antoni A and Antoni B tissue and Verocay bodies (zones of nuclear palisading)
- scotoma island-like gap or blind spot in the visual field; pleural=scotomata
- secondary progressive clinical course of multiple sclerosis that initially is relapsing-remitting and then becomes progressive at a variable rate, possibly with an occasional relapse and minor remission
- secondary symptoms symptoms referable to secondary effects of a lesion e.g., edema, blockage ofcerebrospinal fluid pathways, stretching of vessels
- sectoranopia loss of vision in a wedge of the visual field
- seizure discrete event due to sudden, transient, excessive neuronal discharges in the brain
- sella turcica saddlelike prominence on the upper surface of the sphenoid bone of the skull, situated in themiddle cranial fossa and containing the pituitary gland
- senile plaque see neuritic plaque
- sensory trick specific trigger a patient uses to relieve dystonia, e.g., touching the outer canthus of the eye to temporarily relieve blepharospasm
- septal nuclei neuronal structures in the rostral forebrain adjacent to the septum pellucidum that communicate with the hippocampus, amygdala, hypothalamus,midbrain, habenula, cingulate gyrus, and thalamus septum pellucidum membrane extending ventrally from the body of the corpus callosum that separates the two lateral ventricles from each other setting sun sign forced depression of the eyes due to pressure on the dorsalmidbrainin the setting of hydrocephalus; see also Parinaud’s syndrome
- shadow plaque foci of myelin preservation at the periphery of active multiple sclerosis plaques thought to represent partial remyelination
- Shy-Drager syndrome older term for a variant of multisystems atrophy characterized by preferential degeneration of the intermediolateral cell column of the spinal cord and substantia nigra producing symmetricparkinsonism and autonomic failure
- sialorrhea drooling; increased salivation
- simple tic tic involving a limited number of muscles; simple vocal tics are meaningless noises such as grunting or throat clearing; simple motor tics are focal movements such as eye blinking or facial grimacing
- single fiber electromyography electrodiagnostic test in which potentials of muscle fibers innervated by a single axon are recorded; normal response is for fibers to be activated with consistent latencies whereas inneuromuscular junction disorders, latencies among muscle fibers in a single motor unit are variable (increasedjitter); most sensitive test for myasthenia gravis
- skew deviation hypertropia in which the eyes move vertically in opposite directions due to acquiredsupranuclear or vestibulo-ocular disruption
- sleep latency speed of falling asleep
- sleep paralysis temporary (seconds to minutes) inability to move or talk that occurs during sleep-to-wake or wake-to-sleep transitions; one of the symptoms of narcolepsy, but also experienced by some non-narcoleptic individuals
- slow wave sleep see non-REM sleep smooth pursuit smooth following eye movements that maintain fixation
- solitary nucleus and tract sensory nucleus of the medulla that receives afferent taste information from nerves VII, IX, and X and mediates the gag, cough, carotid sinus, and other visceral reflexes
- soma cell body, which contains the nucleus and endoplasmic reticulum somatosensory evoked potentials (SSEP) series of waves that reflect sequential activation of neural structures along the somatosensory pathways following electrical stimulation of peripheral nerves (typically elicited by stimulation of the median nerve at the wrist, the common peroneal nerve at the knee, and/or the posterior tibial nerve at the ankle and recorded from electrodes placed over the scalp, spine, and peripheral nerves)
- somesthesia sensation
- somnambulism (sleep walking) arising from bed during a period when there is a simultaneous occurrence of incomplete wakefulness and nonREM sleep; typically occurs in the first third of the night during deep sleep
- soporific causing or tending to induce sleep, such as a hypnotic drug
- spike EEG pattern consisting of a transient electrical discharge with a pointed peak and a duration of less than 70 milliseconds that stands out from ongoing background activity; has a strong association with epilepsy spike-and-wave complex generalized synchronous pattern seen on electroencephalogram, consisting of a sharply contoured fast wave followed by a slow wave; seen in generalized epilepsy
- spina bifida failure of bone fusion in the posterior midline of the vertebral column resulting in a bony cleft through which the meninges and varying quantities of spinal cord tissue protrude
- spinal accessory nerve (cranial nerve XI) motor nerve originating partly from the medulla (nucleus ambiguus—innervating laryngeal muscles) and partly from the spinal cord (accessory nucleus in the ventral horn of the cervical cord—innervating the sternocleidomastoid and trapezius muslces); lesion results in weakness in turning the head to the opposite side and elevating the shoulder
- spinocerebellar tract fiber tract originating in the spinal cord and carrying proprioceptive input to theipsilateral cerebellum
- spinothalamic tract axonal tract carrying information on pain and temperature that arises from the posterior nerve roots, which ascend a few segments in Lissauer’s tract before synapsing in the substantia gelatinosa, crossing to the opposite side of the cord in the anterior commisure, and traveling in the anterolateral aspect of the cord up to the thalamus and cortex
- splenium thickened posterior border of the corpus callosum
- spondylosis degenerative disease of the vertebral column that can result in spinal cord compression
- spongiform encephalopathy progressive neurodegenerative disorder associated with various prion agents that produce spongy changes in the brain (e.g., Creutzfeldt-Jakob disease, kuru)
- spreading cortical depression brief wave of intense cortical activation followed by a marked decrease inneuronal activity and reduced blood flow that starts in the occipital cortex and spreads anteriorally at a rate of 2-6 mm/min; thought to underline migraine aura
- status migrainosus migraine attack that persists for > 72 hours and often leads to hospitalization
- stereognosis ability to recognize objects by touch
- stereotypy repetitive stereotyped movements commonly seen in tardive dyskinesia, Tourette syndrome, or autism
- stocking-glove typical distribution on the body where symptoms/signs of peripheral neuropathy are evident (toes to knee and fingers to wrist)
- strabismus misalignment of the eyes that is either developmental (due to a miscalibration of the binocular vergence system in the cerebral cortex at some point in infancy or childhood) or acquired (due to a palsy of a cranial nerve or extraocular muscle)
- stria medullaris white matter tract connecting the anterior hypothalamus and septal nuclei in the medial basalforebrain with the habenula
- stria terminalis white matter tract containing amygdaloid efferents to the septal nuclei in the medial basalforebrain and nuclei of the anterior hypothalamus
- striate cortex see calcarine cortex
- striatonigral degeneration (SND) older term for a variant of multisystems atrophy characterized by degeneration of the striatum and the substantia nigra producing symmetric parkinsonism that does not respond to levodopa or dopamine agonists
- striatum part of the basal ganglia consisting of the caudate and putamen separated by fibers of the anterior limb of the internal capsule
- stroke sudden loss of neurological function caused by a blockage or rupture of a blood vessel to the brain or spinal cord; includes infarction and hemorrhage subtypes
- stupor condition of unresponsiveness from which the patient can only be aroused by vigorous and repeated stimuli; once stimulus ceases, patient lapses back into unresponsiveness
- subarachnoid hemorrhage bleeding in the subarachnoid space most commonly due to trauma or rupture of an aneurysm or arteriovenous malformation
- subarachnoid space actual space separating the pia and arachnoid that surround the brain and spinal cord; contains cerebrospinal fluid, arteries and veins, and filaments of arachnoid matter, giving it the appearance of a spider web
- subclinical seizure electrographic seizure without clinical manifestations subcortical portion of the brain immediately below the cerebral cortex; includes corona radiata, internal capsule, basal ganglia, and thalamus, among others
- subcortical leukoencephalopathy see Binswanger’s disease
- subdural space potential space between the dura and arachnoid that can be filled with blood, cerebrospinal fluid, or pus
- subhyaloid hemorrhage accumulation of blood near the optic disc seen on fundoscopic exam insubarachnoid hemorrhage
- substantia gelatinosa narrow, dense, vertical band of gray matter forming the dorsal part of the posterior column of the spinal cord and serving to integrate the sensory stimuli that give rise to the sensations of pain and temperature
- substantia nigra nucleus in the midbrain tegmentum that is divided into the pars compacta, a region of compactly organized dopaminergic cells that innervate the striatum and cerebral cortex, and the pars reticulata, a region containing loosely organized cells that is a pallidal division of the basal ganglia and sends its output to the thalamus and superior colliculus
- subthalamic nucleus (subthalamus) nucleus in the ventral diencephalon that modulates the output of thebasal ganglia from the internal segment of the globus pallidus to the thalamus
- sulcus groove in the cerebral cortex separating two gyri
- superior cerebellar peduncle (brachium conjunctivum) principle efferent fiber bundle from thecerebellum; fibers decussate in the midbrain and end primarily in the red nucleus and dorsal thalamus; lesions of the caudal SCP before the decussation result in ipsilateral deficits in motor coordination whereas lesionsrostral to the decussation result in contralateral deficits; afferent fibers from the ventral spinocerebellar tracttravel in the SCP to bring proprioceptive information from the lower body to the cerebellum
- superior sagittal sinus venous structure occupying the convex margin of the falx cerebri and draining the upper part of the cerebral hemispheres
- suprasellar above the sella turcica
- Sylvian fissure (lateral fissure or lateral sulcus) prominent long, deep fissure on the lateral surface of thecerebral hemisphere that divides the posterior frontal and anterior parietal lobes from the superior temporal lobe
- sympathetic nervous system part of the autonomic nervous system concerned with preparing the body for fear, fight, or flight; preganglionic fibers arise from the lateral horns of the spinal segments T1-L2
- symptomatic epilepsy epilepsy that is due to a known cause (e.g., tumor)
- syndrome of inappropriate ADH secretion (SIADH) disorder of osmoregulation involving excessive release of arginine vasopressin (antidiuretic hormone), which causes excessive water retention by the kidney, leading to a dilutional hyponatremia; occurs in a wide range of neurological disorders and other medical conditions
- synesthesiacondition associated with involuntary perceptual experiences that are elicited by stimuli that would not be expected to elicit such a response—a crossing of sensory modalities, e.g., experiencing colors in response to numbers, letters, and words
- synucleinopathies
group of neurodegenerative diseases characterized by neuronal or glial inclusions composed of alpha-synuclein; includes idiopathic Parkinson disease and diffuse Lewy body disease - syringobulbia central cavitation (cystic lesion) within the spinal cord (syringomyelia) that extends up to themedulla and pons
- syringomyelia central cavitation (cystic lesion) of the spinal cord, usually in the cervical region, producing a distinctive cape-like distribution of spinothalamic tract sensory loss while leaving the dorsal columns relatively intact
- tau microtubule-associated protein that is functionally modulated by phosphorylation and is hyperphosphorylated in several neurodegenerative diseases.
- teardrop fracture triangular fracture of the anteroinferior aspect of a vertebral body due to axial loading with flexion or extension; often unstable associated with ligamentous injury and/or spinal cord injury
- tectum dorsal surface of the midbrain that contains the superior and inferior colliculi
- teichopsia see fortification spectrum
- temporal lobe epilepsy partial epilepsy arising from the temporal lobe of the brain
- tendon release (tenotomy) surgical procedure involving division of a severely contracted tendon in the management of spasticity
- tension-type headache nonspecific headache that is typically dull, aching, and bilateral, and is often described as a tightening band-like sensation around the head or neck; may be related to muscle tightening in the back of the neck and/or scalp
- tentorium cerebelli fold of dura mater that covers the cerebellum and supports the occipital lobes of thecerebrum
- tetany repetitive, spontaneous axonal discharges at high rates of up to 300 Hz producing intense muscle spasm in the setting of electrolyte or acid-base disturbance
- tetraplegia see quadriplegia
- thalamus large ovoid mass of gray matter in the dorsal aspect of the diencephalon that is located medial to theinternal capsule and caudate and functions as a relay station between the cerebral cortex and the brainstem and spinal cord
- thunderclap headache sudden onset of severe head pain with neck stiffness that may be associated with altered consciousness or focal neurological deficits; suggests subarachnoid hemorrhage
- tilmus see floccillation
- time-intensity profile of the temporal features of a patient’s symptoms that provides clues about etiology of the disease process; acute, subacute, recurrent-remittent, or chronic-progressive
- titubation tremor of the head and neck
- Todd's paralysis temporary (minutes to hours or rarely days) post-seizure mono- or hemiplegia; indicatesseizure was focal onset; sometimes term used for other temporary focal post-seizure deficits, such as aphasia or sensory abnormalities
- tolerance gradual loss of response to a drug with prolonged use
- Tolosa-Hunt syndrome rare painful ophthalmoplegia due to a granulomatous inflammation of the cavernous sinus (paralysis of the third, fourth, and/or sixth cranial nerves) typically relieved by corticosteroids
- tomacula focal area of myelin thickening creating a sausage-like appearance of nerves; common in the geneticneuropathy, Hereditary Liability to Pressure Palsies
- tonic-clonic seizure (grand mal seizure) generalized seizure characterized by initial contraction of the muscles (tonic phase), which may involve tongue biting and urinary incontinence, followed by rhythmic muscle contractions (clonic phase)
- tonic neck reflexes movements and postures of the arm and leg when the neck is bent forwards, backwards, or to the side that are present in normal infants and are incorporated in many bodily movements of normal children and adults
- tonic seizure generalized seizure that involves stiffening of the entire body
- tonsilar herniation herniation of the cerebellar tonsils through the foramen magnum
- torsion see cyclotorsion
- torticollis form of dystonia in which the neck muscles contract involuntarily, causing the head to turn
- Tourette syndrome childhood onset movement disorder characterized by simple or complex tics and often associated with obsessions, compulsions, and attention deficit disorder
- transcortical motor aphasia impairment of language production (non-fluent aphasia) sparing repetition due to a lesion in the anterior extrasylvian region (prefrontal and medial frontal cortex)
- transcortical sensory aphasia impairment of language comprehension (fluent aphasia) sparing repetition due to a lesion in the posterior extrasylvian region (inferior temporo-occipital cortex)
- transcutaneous electric nerve stimulation (TENS) method of pain control involving application of electrical impulses to nerve endings via electrodes that are attached to a stimulator by flexible wires and placed on the skin; thought to block the transmission of pain signals to the brain
- transformed migraine migraine pattern that has changed from episodic to chronic, often related to the overuse of analgesics (medication overuse headache)
- downward displacement of the cerebral hemispheres pushing the diencephalon and midbrainthrough the tentorial notch; symptoms classically follow a rostrocaudal deterioration
- transverse myelitis inflammatory disease involving both sides of the spinal cord in which motor and sensory deficits occur below the level of the lesion; occurs commonly in multiple sclerosis and various infectious and connective tissue disorders
- trigeminal nerve (cranial nerve V) mixed sensory and motor nerve made up of ophthalmic, maxillary, and mandibular divisions responsible for sensation from the face, oral and nasal cavities, and supratentorial dura(but not posterior scalp) and motor innervation of the muscles of mastication; sensory fibers originate in the gasserian ganglion and (1) descend to the upper cervical cord in the spinal tract of V then ascend in the trigeminothalamic tract to the thalamus (pain, temperature, touch), (2) enter the main sensory nucleus of V and ascend to the thalamus (tactile and proprioceptive sensation), or (3) enter the mesencephalic nucleus (jawproprioception)
- trochlear nerve (cranial nerve IV) motor nerve innervating the superior oblique muscle, which depresses and intorts the eye; only cranial nerve to exit dorsally and cross the midline before emerging from thebrainstem—thus a lesion of the nucleus (which is in the caudal midbrain) affects the contralateral eye
- trigonocephaly premature closure of the metopic suture producing bowing of the forehead
- triple flexion spinal reflex consisting of flexion at the hip, knee, and ankle in response to stimulation of the sole of the foot; indicates corticospinal tract lesion
- truncal sensory level level on the trunk below which sensation is impaired; sign of spinal cord lesion
- two-point discrimination ability to detect two stimuli presented simultaneously at decreasing distance as being two separate stimuli; for normal tactile two-point discrimination, the two points of calipers or a paperclip should be recognized at a separation of 2-4 mm on the lips and finger pads, 8-15 mm on the palms, and 3-4 cm on the shins
- U fibers short U-shaped white matter tracts that lie just beneath the cerebral cortex and connect adjacent gyri
- uncal herniation displacement of the uncus of the temporal lobe and the hippocampal gyrus towards the midline and over the lateral edge of the tentorium due to an expanding lesion in the lateral middle cranial fossaor temporal lobe; earliest consistent sign is an ipsilateral dilating pupil due to compression of the ipsilateral third cranial nerve
- uncus most anterior part of the parahippocampal gyrus
- upper motor neuron 1st order neurons that remain in the CNS and synapse with lower motor neurons; lesions result in spasticity, hyperreflexia/extensor plantar response (upgoing toe)
- vacuolar myelopathy vacuolation of myelin in the posterior and lateral columns of the primarily thoracic spinal cord occurring in AIDS and resulting in paraparesis, sensory ataxia, and incontinence; resembles themyelopathy associated with vitamin B12 deficiency
- vagus nerve (cranial nerve X) nerve containing motor, sensory, and parasympathetic fibers; motor fibers originate from the dorsal motor nucleus of the vagus (to innervate the pharynx and the thoracic and abdominal viscera) and the nucleus ambiguus (to innervate the palate, pharynx, and larynx); sensory fibers originate in the nodose ganglion and mediate taste and sensation in the pharynx and thoracic and abdominal viscera
- vascular dementia dementia with a stepwise deteriorating course and a patchy distribution of neurological deficits caused by cerebrovascular disease; includes multi-infarct dementia and Binswanger’s disease
- vasospasm blood vessel constriction in response to irritative stimuli
- vegetative state subacute or chronic condition following coma and consisting of return to wakefulness but apparent total lack of cognition
- ventral anterior ventral horn see anterior horn ventricles four cerebrospinal fluid filled cavities (paired lateral, third, and fourth) deep with the brain that communicate with each other and with the central canal of the spinal cord and the subarachnoid space
- vergence movement of the eyes in opposite directions so that images of an object are placed on both foveasand thus appear single
- vergence (dysconjugate eye movements) movement of both eyes in different directions at the same time; includes 2 types: convergence and divergence
- vermis median region of the cerebellum lying between the cerebellar hemispheres
- version (conjugate eye movements) movement of both eyes in the same direction at the same time; includes 4 types: saccade, smooth pursuit, optokinetic nystagmus movements, and vestibulo-ocular responsemovements
- vertebral artery paired arteries that arise from the subclavian arteries and fuse to form the basilar artery on the ventral surface of the brainstem; supply blood to the lower brainstem and posterior cerebellum.
- vestibulocochlear nerve (cranial nerve VIII) sensory nerve carrying information from the semicircular canals, utricle, and saccule to mediate equilibrium and hearing
- vestibulo-ocular response see oculovestibular response
- Virchow-Robin Spaces perivascular extensions of subarachnoid space
visual acuity measurement of the eye’s ability to distinguish details; typically expressed as a fraction in which the numerator (20) indicates that the subject is standing at 20 feet from a normal test object and the denominator is the distance from which a normal subject can read the same normal image .
- visual evoked potentials (VEP) series of waves that reflect sequential activation of neural structures along the visual pathways following checkerboard stimulation; most useful in screening for optic nerve pathology (e.g., optic neuritis) and less useful in postchiasmatic disorders
visual fields entire area visible to an eye that is fixating straight ahead
- Wallenberg syndrome see lateral medullary syndrome
- Wallerian degeneration stereotyped degenerative reaction of axons and Schwann cells distal to a site of mechanical damage; occurs simultaneously in many of the axons in a fascicle
- watershed infarct infarct occurring in brain tissue that receives blood supply from the distal portions of two major arteries; generally a result of global hypoperfusion
- Weber Syndrome ipsilateral oculomotor palsy and contralateral hemiplegia due to ventral midbrain lesion affecting the III nerve fascicles and cerebral peduncle
- wet keratin nodules composed of often calcified stacks of keratin characteristic of craniopharyngiomaWernicke’s aphasia see fluent aphasia
- West’s syndrome epilepsy syndrome characterized by infantile spasms, mental retardation, andhypsarrhythmia on EEG; begins before 1 year of age
- WHO grade
scheme for grading central_nervous_system neoplasms histologically developed by the World Health Organization
benign
low grade (atypia only)
intermediate grade (mitotic activity)
high grade malignant (necrosis or endothelial proliferation,
typically with atypia and mitosis) - xanthochromia yellowish discoloration of cerebrospinal fluid resulting from lysis of red blood cells seen ~ 12 hours to 2 weeks after subarachnoid hemorrhage
neurilemma thin membrane surrounding the axons and myelin of peripheral nerves; outermost layer of nerve fibers
neuromelanin dark brown pigment seen in selected neuronal populations (most characteristically in the substantia nigra and locus ceruleus) that represents the residua of catecholamine metabolism
neuronophagia engulfing of degenerating neurons by hematogenously derived monocytic cells and activatedmicroglia
optic disc (optic nerve head) location where all the ganglion cells exit the retina to form the optic nerve; known as the blind spot since there are no receptors in this part of the retina
perimetry visual field testing designed to determine the sensitivity of specific locations of peripheral and central vision
Pott’s disease tuberculous involvement of the vertebral column with vertebral collapse
repetitive nerve stimulation nerve conduction study in which a brief series of shocks is applied to a motor nerve before and after brief exercise of a muscle supplied by that nerve; useful for evaluating disorders of neuromuscular transmission such as myasthenia gravis (decremental response see) and Lambert Eaton myasthenic syndrome (incremental response seen).
spina bifida occulta closed spinal dysraphism characterized by posterior vertebral defect and various overlying cutaneous anomalies (e.g., lipoma, patch of hair); often associated with other spinal cord abnormalities spinal dysraphism failure of bone fusion in the posterior vertebral column; classified as open (not covered by skin) or closed (covered by skin); see also meningocele and myelomeningocele spinocerebellar ataxia group of hereditary neurodegenerative disorders caused by expansion of a CAG triplet repeat and characterized by progressive ataxia and variable other features such as neuropathy and hearing or visual loss
tauopathies group of neurodegenerative diseases characterized predominantly by abnormalities of tau protein; includes frontotemporal dementia, progressive supranuclear palsy,
tethered cord attachment of the spinal cord to the vertebral column or subcutaneous tissues by a thickenedfilum terminale, fibrous band, diastematomyelia, dermal sinus tract, or lipoma resulting in a low-lying conus medullaris (i.e., below the L2-3 interspace)
Wernicke’s encephalopathy syndrome of confusion/short-term memory loss, ophthalmoplegia (especially abducens palsy), and ataxia due to thiamine deficiency, occurring in the setting of alcoholism, starvation, or protracted vomiting; may progress to coma if untreated; associated with neuronal damage that is most prominent in the mammillary bodies, inferior colliculus, and thalamus
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