Glossary of common neurologic terms 

Accommodation – Sensory nerves having dynamic firing rates that decline with time even though the stimulus is maintained. Changes in the eye that enable clear vision at various distances.

Afferent pathway – Axons leading to the brain or spinal cord.

Agnosia – Lack of knowledge and is synonymous with an impairment of recognition. An example is visual agnosia in which patient cannot arrive at the meaning of previously known nonverbal visual stimuli despite normal visual perception and alertness.

Agraphia – Inability to recognize numbers/letters written on the palm or fingertips.

Alexia – Acquired reading impairment that may be accompanied with writing deficits (alexia with agraphia) or without writing deficits (alexia without agraphia).

Allodynia – Non-painful cutaneous stimuli causing pain.

Amaurosis fugax – Transient monocular blindness. This usually comes from an internal carotid artery embolus temporarily occluding the ophthalmic artery.

Amnesia – Partial or complete loss of the ability to learn new information or to retrieve previously acquired knowledge.

Amyotrophy – Wasting of muscles usually from denervation.

Anal reflex – Reflexive contraction of anal sphincter upon perianal sensory stimulation.

Aneurysm – Abnormal dilatation or bulging of an intracranial artery wall, usually at bifurcations of the Circle of Willis.

Anisocoria – Unequal pupil size.

Ankle jerk – Deep tendon reflex (Achilles reflex) elicited by striking the Achilles tendon at the ankle resulting in foot plantar flexion.

Anterior horn – Gray matter in the ventral spinal cord that contains neurons including anterior horn cells (lower motor neurons).

Anterior root – Segment of motor nerves composed of anterior horn neurons exiting the ventral spinal cord to where they join the mixed peripheral nerve.

Anton’s syndrome – Lesions involving the occipital and parietal lobes that produce blindness or a homonymous hemianopia that is denied by the patient.

Aphasia – Disorder of expression or comprehension of spoken language due to dysfunction of language centers in dominant cerebral cortex or thalamus.

Apoptosis – Genetically programmed neuronal cell death that may be normal or abnormal.

Apraxia – Inability to perform a learned act, despite demonstrated ability to perform components of the act usually due to dysfunction of a parietal lobe.

Arteriovenous malformation (AVM) – Abnormal blood vessel complex consisting of arteries, veins, and capillaries located in the brain or spinal cord that often hemorrhage.

Arteritis – Inflammation of walls of arteries.

Astereognosis – The inability to distinguish and recognize small objects based on size, shape, and texture when placed in the hand that has normal primary tactile sensory input.

Ataxia – Incoordination of limb or body movements, particularly gait, often due to impairment of cerebellar function.

Athetosis – Involuntary movements characterized by slow, sinuous, twisting of arms, legs, or body.

Atrophy – Wasting of muscle/s from disuse or denervation.
Autism – Childhood illness affecting language and interpersonal relationships.

Babinski sign – Extensor response of the great toe with fanning of the other toes in response to stimulus on sole of foot. The extensor plantar response is normal in infants to about 9 months, thereafter reflects damage to the corticospinal tract (upper motor neuron sign).

Basal ganglia – Deep gray matter nuclei of the cerebral hemispheres comprising putamen, caudate, globus pallidus, subthalamic nucleus, substantial nigra, and often thalamus.

Biceps reflex – Deep tendon reflex elicited by hitting the biceps tendon resulting in brief contraction of the biceps muscle.

Brachioradialis reflex – Deep tendon reflex elicited by hitting the distal radius resulting in brief contraction of the brachioradialis muscle.

Bradykinesia or Akinesia – Difficulty in moving despite intact motor nerves and normal muscles as seen in Parkinson’s disease.

Broca’s aphasia – Motor speech disorder (expressive aphasia, nonfluent or anterior aphasia) due to dysfunction located in the dominant frontal lobe and characterized by effortful, sparse, agrammatic, halting, truncated speech with loss of normal language melody.

Bruit – Sound due to turbulence of blood passing a narrow artery segment, often heard from the internal carotid artery in the neck.

Bulbar – Refers to the medulla and pons of the lower brainstem.

Calcarine cortex – Primary visual cortex located in the medial occipital lobe.

Caloric test – Placement of warm or cool water in the external canal to evaluate eye movements from stimulation of the vestibulo-ocular reflex.

Cauda equina – Lumbosacral nerve roots in the lumbar and sacral vertebral canal before the exit via neural foramina.

Caudal – Lower in the neural axis compared with other structures of the same kind nearer the head.

Charcot-Marie-Tooth disease – Dominant autosomal genetic disease affecting distal myelinated axons of limbs, especially legs producing distally symmetrical polyneuropathy.

Cheyne-Stokes respirations – Regular cyclic oscillations of breathing between hyperpnea or over breathing and apnea.

Chorea – Abnormal involuntary movements characterized by rapid flicks or jerks of limb, face, or trunk muscles.

Chromatolysis – Disintegration of chromophilic substance or Nissl body from neuron when the axon is divided.

Cogwheel rigidity – Ratchet-like increased resistance to passive movement (hypertonia) usually found at the wrists of patients with Parkinson’s disease.

Computerized tomography (CT) – Neuroimaging technique based on computer processing of data from differential attenuation of x-ray beam passing through tissue (often the skull & brain) that produces a series of slices through the tissue.

Constructional apraxia – Disturbances in organizing parts of a complex object.

Corticobulbar tract – Descending cortical motor tract traveling to a brainstem motor nucleus.

Corticospinal tract – Descending cortical motor tract primarily from motor cortex that descends down the spinal cord to synapse at anterior horn cells or adjacent interneurons.

Countercoup – Injury to brain on opposite side as head trauma.

Coup – Injury occurring to brain on same side as head trauma.

Decerebrate posture – Both arms and legs are extended, especially when painful stimuli are administered usually due to a lesion that separates upper from lower brainstem.

Decorticate posture – Flexion of one or both arms and extension of ipsilateral or both legs due to lesion that isolates brainstem from contralateral or bilateral cortical influences.

Deep tendon reflexes (DTR) – Term used to describe a monosynaptic stretch reflex elicited by tapping a tendon with resulting muscle contraction.

Demyelination – Primarily loss of the axon nerve sheath in the peripheral or central nervous system with relative sparing of the underlying axon. Segmental demyelination implies that the myelin loss is patchy along the nerve leaving part of the axon with intact myelin.

Dizziness – General term to describe sensation of light-headedness or feeling off balance.

Doll’s eyes maneuver – Vestibulo-ocular reflex that is performed usually in comatose patient where the head is rotated laterally but the eyes remain stationary and do not move with head.

Dominance -Term that refers to cerebral hemisphere that controls language and principle limb involved in writing, eating, and throwing.

Dorsal column nuclei – Nucleus gracilis and cuneatus in the caudal medulla that contain 2nd order neuronal cell bodies for the dorsal columns in the spinal cord and usually conduct position sense, vibration, and touch sensations.

Dorsal horn – Dorsal (posterior) aspect of the spinal cord gray matter that contains neurons associated with peripheral afferent sensory fibers.

Dorsal root – Part of the peripheral afferent sensory nerve between the dorsal root ganglia and the dorsal horn of the spinal cord.

Dorsal root ganglia – Cluster of 1st order peripheral afferent sensory neuron cell bodies located at each segmental level near vertebral bodies.

Dressing apraxia – Lesions only involving the non-dominant parietal lobe that produce neglect on one side of the body in dressing and grooming.

Dysarthria – Impaired articulation of speech that sounds like “speaking with rocks in your mouth”

Dyskinesia – Several involuntary movements of limbs or face that include chorea, athetosis, tics, and dystonia.

Dysmetria – Limb ataxia in directed movement that misses the target.

Dysphagia – Impairment of swallowing.

Dysphonia – Difficulty in speaking, often with a low speech volume.

Dystonia – Strong, sustained, and slow contractions of muscle groups that cause twisting or writhing of a limb or the entire body. The contractions are often painful and may appear disfiguring. The dystonia lasts seconds to minutes and occasionally hours producing a dystonic posture.

Edema – Excess water in the brain from swelling of cell bodies (cytotoxic) or increased fluid in extracellular spaces (vasogenic).

Efferent pathway – Axons leading away from the brain or spinal cord.

Electroencephalograph – Instrument for recording minute electrical currents developed in the brain by means of electrodes attached to the scalp.

Electronystagmograph – Instrument for recording electrical signals generated by eye movements or nystagmus during tests to evaluate patients with vertigo.

Epilepsy – Illness resulting from repetitive seizures due to abnormal brain electrical activity that is often subdivided into specific seizure types (e.g., generalized tonic-clonic).

Epley maneuver – In patients with benign paroxysmal positional vertigo, a variation of the Hallpike maneuver is performed to roll loose otoconia around the posterior semicircular canal eliminating the recurrent brief vertigo spells.

Extraocular movements – Eye movements due to contraction of extraocular eye muscles rather than muscles that govern the iris and lens.

Falx cerebri – Rigid dural fold in midsagittal plane that separates the two hemispheres.

Fasciculation – Contraction of fascicle (group) of muscle fibers innervated by single nerve from one anterior horn neuron that produces visible intermittent spontaneous twitching of part of a muscle but does not move the body part.

Fibrillation – Spontaneous contraction (invisible to the eye but detected by EMG) of individual denervated muscle fibers no longer under the control of a motor nerve.

Flaccid – Limp muscle that has no muscle tone.

Foramen magnum – Large opening at base of skull where spinal cord and brainstem join.

Fovea – Central part of macula of retina related to sharpest vision for reading.

Frenzel glasses – Strong positive lenses that inhibit patients from seeing clearly enough to fixate but allow the examiner to see the eye. Glasses used to detect nystagmus.

Gadolinium – Rare earth compound given intravenously before MRI to detect brain areas that have a broken blood-brain barrier (such as at tumors).

Ganglia – Clusters of neurons all having similar function, such as dorsal root ganglia.

Gerstmann’s syndrome – The inability to designate or name the different fingers of the two hands, confusion of the right and left sides of the body and inability to calculate or to write.

Glasgow coma scale – Simple scoring system of unconscious patients based on eye opening, motor response, and verbal response that is useful for prognosis.

Glia – Term for supporting cells of CNS that includes astrocytes and oligodendroglia.

Glioma -Term used for CNS tumors of astrocyte or oligodendrocyte lineage.

Global aphasia – Acquired loss of ability to comprehend or produce verbal messages.

Gower’s maneuver – Seen in muscular dystrophy where an individual with weak proximal leg muscles places his hands on the knees and climbs up his thighs to stand.

Grasp reflex – Involuntary grasping of the hand when the palm is stimulated. This is normal in babies but abnormal in older children and adults and is often associated with diffuse frontal lobe damage.

Gray matter – Term that refers to gray color of part of CNS that contains neurons rather than white matter that contains mainly axons and myelin sheaths.

Hallpike maneuver – A test to detect positional nystagmus performed by laying a patient down with their head hanging below the table.

Hammer toes – Cocking up of toes like gun hammers often due to a distal sensorimotor polyneuropathy causing atrophy and weakness of intrinsic flexor toe muscles with overriding pull of more proximal extensor toe muscles.

Hemianopia – Refers to loss of vision in half the visual field in the vertical plane. If both eyes are equally involved, it is called homonymous hemianopia.

Hemiparesis – Incomplete weakness involving one side of body.

Homer’s syndrome – Miosis, ptosis, and diminished sweating on the ipsilateral face due to lesion in the 3rd neuron pathway starting in hypothalamus and traveling to the brainstem, thoracic spinal cord, cervical sympathetic ganglion, and sympathetic nerves along the carotid and ophthalmic arteries.

Hydrocephalus – Abnormal enlargement of one or more ventricles of the brain. Obstructive hydrocephalus is when there is obstruction of CSF flow in ventricular system or subarachnoid space. Hydrocephalus ex vacuo refers to passive ventricular enlargement from loss of surrounding white matter and neurons. Communicating hydrocephalus refers to nonobstructed pathway from spinal subarachnoid space to lateral ventricles.

Hypertonia – Increased muscle tone or resistance produced by passive movement of a limb on a joint.

Hypotonia Decreased muscle tone or resistance produced by passive movement of a limb on a joint.

Hypsarrhythmia – Random, high-voltage slow waves and spikes seen on EEG that vary from in time and location.

Ice water caloric – Test used in comatose patients to determine whether the pathway from the vestibular inner ear to the 3rd and 6th cranial nerves is intact. When pathway is intact, ice water irrigated in one ear produces bilateral eye movement to the ipsilateral side.

Infantile spasms – Brief, symmetric contractions of neck, trunk, and limb muscles seen in infants (also called salaam seizures).

Ischemic penumbra – Area of brain around an acute stroke that immediately has insufficient blood flow to function but sufficient to prevent cell death and may or may not subsequently die.

Jaw jerk – Corticobulbar reflex produced by tapping downward on the chin with resulting contraction of masseter muscles and upward jaw movement. When unusually brisk, the jaw jerk implies an upper motor neuron abnormality in corticobulbar tract to 5th cranial nerve nuclei.

Kernicterus – Deposition of bile pigment in deep brain nuclei with neuronal degeneration from neonatal jaundice.

Knee jerk (KJ) – The patellar reflex is a deep tendon reflex in which the patellar tendon is tapped causing a brief extension of the leg.

Korsakoff’s syndrome or psychosis – Loss of the ability to learn new memories with a tendency to fabricate answers. It is usually part of Wernicke-Korsakoff’s encephalopathy from alcoholism.

Lateral geniculate body (nucleus) – Thalamic nucleus that receives input from optic nerves and sends outward optic radiations to the occipital cortex and upper brainstem.

Lateral medullary syndrome – Infarction of dorsolateral medulla and inferior cerebellum due to occlusion of posterior inferior cerebellar artery, a branch of the vertebral artery.

Lenticular (lentiform) nucleus – Combination of the putamen and the globus pallidus.

Leukomalacia – Abnormal softening of white matter areas.

Lordosis – Curvature of the spinal column with a forward convexity.

Lower motor neuron – Motor neurons in the anterior horn of the spinal cord or brainstem that directly innervate muscles.

Lumbar puncture – Placement of a hollow needle with a stylet into the spinal canal in the lower lumbar space to withdraw cerebrospinal fluid or instill medications.

Magnetic resonance imaging (MRI) – Use of changing magnetic fields to create brain images as brain slices in any plane.

Meralgia paresthica  – Sensory impairment and dysthesias in the skin distribution of the lateral femoral cutaneous nerve of the thigh.

Mesial temporal sclerosis – Progressive loss of neurons and gliosis in one hippocampus that often causes complex partial seizures.

Miosis – Abnormal constriction of a pupil.

Mononeuropathy – Lesion involving a single peripheral nerve.

Mononeuropathy multiplex – Lesions involving more than one peripheral nerve.

Myalgia – Muscle aches and pains that are not cramps.

Myelin – Lipid-protein sheath that wraps some peripheral nerves that is made by Schwann cells and some central nerves that is made by oligo-dendroglia.

Myeloradiculopathy – Disease process affecting the spinal cord, adjacent peripheral nerve roots, and nerves.

Myoclonus – Rapid, brief muscle jerks involving specific muscles or the entire body that do not blend together and are shorter duration than chorea. Nocturnal myoclonus is the normal abrupt body jerks that occur when an individual is falling asleep. The electroencephalogram may or may not have spikes correlating with the myoclonus.

Myopathy – General term implying disease of muscle from any cause.

Myotonia – Abnormal sustained muscle contractions with slow relaxation that have a characteristic pattern on electromyogram.

Neglect – Inability to attend normally to a portion of extrapersonal or intrapersonal space or both that cannot be explained by altered perception. In visual neglect, the patient ignores objects, persons, or movement in the left or right of the environment.

Neuraxis – Longitudinal axis of the central nervous system that runs from the rostral forebrain to the caudal spinal cord.

Neuronophagia – Destruction of neurons by phagocytic cells.

Neuropathy – Term that describes disorders of peripheral nerves.

Nocioceptive – Sensory receptors that respond to painful stimuli.

Non-convulsive status epilepticus – Complex partial status epilepticus where the patient has constant confusion and impaired awareness but can move his limbs.

Nystagmus – Oscillatory eye movements that may be physiologic (following spinning in a circle) or abnormal (from inner ear, brainstem, and cerebellar dysfunction).

OD– Right eye.

Ophthalmoplegia – Paralysis of eye movements.

Oriented x 3 – Oriented to person, place, and time in mental status testing.

Orthostatic hypotension – Fall in blood pressure upon standing causing dizziness or even syncope.

OS Left eye.

Otoconia – Tiny calcium carbonate crystals embedded in a gelatinous matrix above the macula of the utricle and saccule that move with gravity changes bending attached hair cells allowing detection of gravity.

Otorrhea – CSF drainage from ear.

Papilledema – Swelling of optic nerve disc from elevated intracranial pressure.

Paraphasias – Mispronounced or inappropriately substituted words with sematic paraphasias being errors based on meanings of words (aunt for uncle) and literal paraphasias being errors based on sounds (hook for took).

Paresthesias – Spontaneous firing of peripheral nerve fibers causing a tingling sensation.

Paroxysmal – Sudden event, as in spikes on electroencephalogram.

Past pointing – Repeated missing a target by going too far or off to one side when using a finger or toe with closed eyes that is due to dysfunction of the vestibular system or cerebellum.

Patellar reflex – Knee jerk reflex is a deep tendon reflex in which the patellar tendon is tapped causing a brief extension of the leg.

Peripheral nervous system (PNS) – All neural structures that lie outside the spinal cord and brainstem and includes motor, sensory, and autonomic nerves and their ganglia.

PERRLA – Abbreviation for pupils equal, round, and reactive to light and accommodation.

Phlebitis – Inflammation of veins.

Phonophobia – Discomfort from noises that normally do not cause discomfort.

Photophobia – Abnormal eye pain from bright lights.

Polyneuropathy – Diffuse and symmetrical distal dysfunction of sensory, motor, and autonomic nerve axons that usually begins in the feet.

Positron emission tomography (PET) – Imaging technique that detects emissions from injected radiolabeled compounds to create a quantifiable image of blood flow, glucose utilization, or location of specific ligands that attach to brain receptors, etc.

Prefrontal lobe – Part of brain anterior to the motor and premotor cortex that is a multisen-sory association cortex.

Prion – Abnormal protein configuration of a normal host protein that causes transmissible spongiform encephalopathies, like Creutzfeldt-Jakob disease.

Proprioception – Sense of position of body part relative to fixed object like a floor that is both unconscious and conscious.

Prosopagnosia – Inability to recognize familiar faces (facial agnosia).

Pseudobulbar palsy – Syndrome that affects speech articulation, phonation, swallowing, and emotional lability due to bilateral dysfunction of corticobulbar tracts in the brainstem.

Psychomotor retardation – Abnormal slowing of mental behavior and limb movements that is not due to mental retardation.

Ptosis – Abnormal drooping of one or both eyelids.

Putamen – Part of basal ganglia. The caudate and putamen form the striatum and putamen and globus pallidus from the lentiform or lenticular nucleus.

Quadrantanopia – Loss of vision in one quadrant of vision.

Radiculopathy – Damage to a nerve root leaving the spinal cord that causes weakness, sensory loss or dysesthesias, and diminished reflex in corresponding myotome and dermatome.

Ramsay Hunt syndrome – Acute facial weakness due to herpes-zoster virus reactivation from the geniculate ganglion.

Rigidity – Constant resistance to muscle stretching in both flexors and extensors throughout range of motion due to the stretching force inducing some motor units to are. In Parkinson’s disease, rapid flexion and extension of wrist or elbow often elicits a ratchet-like feeling (cogwheel rigidity).

Rinne test – Comparison of bone conduction (placing a vibrating tuning fork on the mastoid process) to air conduction in which air conduction normally is heard better.

Rolandic fissure – Fissure that separates the motor cortex in the frontal lobe from the sensory cortex in the parietal lobe.

Romberg sign – Ability to stand with feet together and eyes open and the inability to maintain posture with the eyes closed.

Rooting reflex – Normal turning of infant’s face and lips toward a nipple touching the cheek but abnormal “frontal release reflex” when seen in adults upon touching the cheek.

Rostral – Direction or position of neuroaxis towards the forebrain and away from the caudal spinal cord.

Saccadic eye movement – Fast eye movement, voluntary or reflex, usually accomplishing foveal fixation.

Salaam seizures – Brief, symmetric contractions of neck, trunk, and limb muscles seen in infants (also called infantile spasms).

Saltatory conduction – Nerve action potential that moves down a myelinated nerve by jumping from node of Ranvier to node of Ranvier, increasing conduction velocity to as fast as 80 meters/second.

Sciatica – Term for radiating pain down a leg from damage to one or more lumbosacral nerve roots that form the sciatic nerve.

Semicircular canals – Three canals at right angles to each other and located in the temporal bone detect angular acceleration and serve to keep eyes steady during head movement.

Shunt – Tubing used to move cerebrospinal fluid that is blocked along its pathway (usually a ventricle) to the abdomen or jugular vein where it can be absorbed.

Single photon emission computed tomography (SPECT) – Imaging system that is similar but cheaper than positron emission tomography that qualitatively determines regional blood flow or brain metabolism relative to other brain areas.

Skew deviation of vision – Vertical and slightly horizontal (diagonal) double vision that is the same in all fields of gaze due to a brainstem lesion.

Snout reflex – Pouting of lips following tapping the lips.

Spasticity – Condition resulting from damage to the corticospinal tract in which at-rest muscles are in midposition and limbs held in a characteristic flexed posture. Rapid passive limb movement initially produces little resistance but then quickly has increasing muscular resistance to a point when the resistance suddenly disappears (“clasp-knife” phenomena).

Stenosis – Narrowing of lumen of artery or spinal canal.

Strabismus – Lack of eye alignment such that the two visual axes assume positions relative to each other different from that required by the physiologic task.

Straight leg raise test -Test for lumbar radiculopathy in which passive elevation of a straightened leg produces pain in the lower back.

Striate cortex – Primary visual cortex.

Striatum – Combination of the caudate nucleus and the putamen.

Subfalcial space – Space beneath the falx in which the cingulate gyrus can herniate from increased intracranial pressure.

Suck reflex – Normal sucking response of infants when touching the lips but abnormal “frontal-release” reflex in adults when touching the lips elicits a sucking response.

Sylvian fissure – Major horizontal fissure that separates the temporal lobe from adjacent parts of the frontal and parietal lobes.

Tandem gait – Walking heel to toe in a straight line.

Tics – Abrupt, transient, repetitive, stereotypical movements of face and limbs or vocalizations that may be briefly voluntarily suppressed but is often then followed by a burst of tics when the suppression is removed.

Tonsillar herniation – Downward movement of cerebellar tonsils into the foramen magnum in response to increased intracranial pressure from localized mass in the posterior fossa.

Tonsils – Most inferior part of the midline cerebellum.

Transient ischemic attack – Focal neurologic signs from transient occlusion of a cerebral artery that usually last less than an hour but always less than 24 hours.

Triceps jerk – Deep tendon reflex elicited by tapping the triceps tendon above the back of the elbow.

Uncal herniation – Movement of the uncal gyrus of the medial temporal lobe under the tentorial notch in response to mass in the temporal-frontal lobes producing increased intracranial pressure.

Upper motor neuron – Neurons in the upper brain that synapse with lower motor neurons in the brainstem or spinal cord.

Utricle – Part of the inner ear that detects gravity.

Valsalva maneuver – Increase in intrapulmonic pressure by forcible expiration against a closed glottis.

Ventricles – Four cerebrospinal fluid-filled cavities in the brain (lateral ventricles, third ventricle and fourth ventricle) along the cerebrospinal fluid pathway.

Vermis – Midline part of the cerebellum that participates in truncal balance and gait.

Vertigo – Illusion of abnormal spinning movement by the individual or his environment.

Watershed brain territory – Cerebral cortex located between the distal ends of the middle and posterior cerebral arteries (parietal lobe) and middle and anterior cerebral arteries (anterior frontal lobe) that are damaged when hypoperfusion of the brain occurs.

Wernicke’s aphasia – Language disorder in which there is loss of ability to comprehend verbal or written communications and ability to speak in fluid sentences with normal melody that make no sense.

White matter – Central nervous tissue that contains mainly myelinated (white appearing) nerve fibers, but not their neuronal cell bodies.

Xanthochromia  – Yellow color of CSF supernatant that comes from lysed RBCs, bilirubin, or very elevated CSF protein concentration.