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  • a

  • Abduct
    Pronunciation: ab·duct / (ab-dukt´) Definition: To move away from the sagittal midline
  • Absence seizure
    Generalized seizure characterized by suddenly freezing in position, staring off into space, and impaired consciousness. Unclear if these occur in dogs & cats.
  • Accomodation
    Pronunciation: ac·com·mo·da·tion/ (ah-kom″ah-da´shun) Definition: Adjustment of the focal length of the lens of the eye to focus on objects at varying distances
  • Action potential
    A rapid, transient, all-or-none electrical impulse generated by a neuron at the axon hillock propagated toward the synapse.
  • Action tremor
    A tremor that occurs only during movement of an affected body part
  • Adduct
    Pronunciation: ad·duct/ (ah-dukt´) Definition: To move toward the sagittal midline
  • Afferent
    Pronunciation: af·fer·ent / (af´er-ent) Definition: proceeding from the periphery toward the central nervous system
  • Allodynia
    A condition in which the patient experiences pain to a stimulus that would normally be non-painful
  • Analgesia
    Loss of pain sensation
  • Anencephaly
    CNS malformation with absence of the forebrain, resulting from failure of closure of the cephalic end of the neural tube during development
  • Anhidrosis
    Absence of sweating
  • Anisocoria
    Inequality in pupil diameter
  • Anosmia
    Loss of sense of smell
  • Aphonia
    Complete loss of voice
  • Arachnoid
    Middle layer of meninges (arachnoid mater) surrounding the brain and spinal cord. CSF is located between the pia mater and arachnoid mater.
  • Arachnoid villi
    Tufts of arachnoid mater that extend through the dura mater into the veins or venous sinuses; one of the major routes of CSF reabsorption
  • Arteriovenous malformation
    Cluster of abnormal arteries and veins
  • Arteritis
    Inflammation of arteries
  • Ascending reticular activating system
    A collection of neurons in the central core through the entire length of the brainstem that is responsible for arousal and consciousness
  • Ataxia
    Incoordination; typically a sensory phenomenon; There are three types of ataxia: general proprioceptive, vestibular, and cerebellar.
  • Athetosis
    Involuntary, slow, writhing movements
  • Autonomic nervous system
    A subdivision of the peripheral nervous system that regulates homeostasis and visceral function; there is no voluntary control over this system
  • Axonopathy
    A disorder characterized by degeneration of the axon
  • b

  • Basal ganglia
    Deep cerebral nuclei, including the caudate nucleus, putamen, globus pallidus, subthalamus, and substantia nigra
  • Basilar artery
    Large artery ventral to the brainstem formed by fusion of the two vertebral arteries; one of the main sources of blood supply to the brain
  • Bell's palsy
    An inflammatory disorder of the facial nerve in man resulting in lower motor neuron facial muscle weakness, hyperacusis, impaired taste and impaired lacrimation. It is thought to be due to reactivation of Herpes simplex virus. Clinically similar to Idiopathic Facial Paralysis in dogs.
  • Blepharospasm
    Repetitive involuntary blinking of the eyelids
  • Brainstem auditory evoked response
    Series of electrical responses arising from various structures in the auditory pathway recorded at the skin following repetitive stimulation of the ears via a clicking sound; used as a screening test for deafness; can be used as one tool to determine brain death
  • Bulbar
    Relating to lower cranial nerve nuclei
  • Butterfly glioma
    A glioma that crosses midline via a white matter commissure leading to a bihemispheric mass lesion with the appearance of wing-like extensions
  • c

  • Catamenial
    Refers to menses; in neurology, the term is used most often to in catamenial epilepsy in which seizures are occur or are worse during specific times of the estrus cycle
  • Cataplexy
    Sudden loss of postural tone resulting in collapse, often occurring with excitement or stress; frequently occurs with narcoplepsy
  • Cauda equina
    Collection of nerve roots within the vertebral canal after termination of the spinal cord that supply the pelvic limbs and pelvic structures; cauda equina literally means "horse's tail"
  • Caudal
    Toward the tail
  • Caudate
    One of the basal ganglia (deep cerebral nuclei) that is located on the ventral to the floor of the lateral ventricles
  • Caudotentorial
    Lesion caudal to the tentorium cerebelli in the pons, medulla, or cerebellum
  • Cavernous sinus
    Paired venous structures on either side of the sella turcica surrounding the pituitary gland
  • Central cord syndrome
    Spinal cord injury in which the central region (gray matter) is more severely affected, resulting in thoracic limb weakness that is more severe than pelvic limb weakness
  • Central nervous system
    brain and spinal cord
  • Centrum semiovale
    Large region of white matter dorsolateral to the lateral ventricle between the internal capsule and corona radiata
  • Cerebellar herniation
    Displacement of cerebellar tissue caudally into or through the foramen magnum (caudal cerebellar herniation) or rostrally under the tentorium cerebelli (rostral cerebellar herniation)
  • Cerebellum
    Structure in the caudal fossa dorsal to the pons and medulla; responsible for rate and range of motion; receives input and sends output to and from the cerebrum, brainstem, and spinal cord
  • Cerebral cortex
    Outermost layer of the cerebral hemisphere consisting of a convoluted layer of gray matter
  • Cerebral hemisphere
    One half of the cerebrum which contains the cerebral cortex, basal ganglia, hippocampus, amygdala and other structures
  • Cerebrospinal fluid
    Clear, colorless fluid surrounding the brain and spinal cord; functions to provide nutrition to the brain, immunologic protection, and acts as a shock absorber; also an important determinant in cerebral autoregulation of cerebral blood flow
  • Chorea
    Involuntary, irregular, rapid jerking movements
  • Choroid plexus
    Tufts of modified ependymal cells and capillaries extending into the ventricles; secretes cerebrospinal fluid
  • Choroid plexus tumor
    A benign (papilloma) or malignant (carcinoma) tumor arising from the choroid plexus
  • Cingulate gyrus
    A gyrus located dorsal to the corpus callosum on midline; a cortical component of the limbic system involved in emotional and cognitive processing
  • Coma
    Mental status characterized by being unresponsive to noxious stimuli
  • Complex partial seizure
    Partial seizure with impaired consciousness or awareness
  • Concussion
    Traumatic closed brain injury resulting in temporary neurologic impairment and often a transient loss of consciousness
  • Conduction block
    Failure of action potential conduction along an anatomically-intact axon
  • Contracoup
    Injury opposite to the side of impact
  • Contracture
    Permanent shortening of muscles and tendons
  • Contralateral
    Occurring on the opposite side of the body
  • Conus medullaris
    Tapered, caudal-most portion of the spinal cord
  • Corona radiata
    Fan-like white matter projections into and out of the cerebral cortex
  • Corpus callosum
    Largest of the cerebral commissures; primarily connects neopallium (cerebral cortex) on each side
  • Cortical blindness
    Blindness due to bilateral cerebral disease, especially the primary visual cortex in the occipital lobes
  • Corticobulbar
    Axons projecting from the cerebrum to lower motor neurons in the brainstem
  • Coup
    Injury on side of impact
  • Craniectomy
    Surgical removal of a bone flap to access the brain; bone flap not replaced at the end of surgery
  • Cranioplasty
    Surgical repair of a defect or deformity of the skull, for example following removal of multilobular tumor of bone
  • Craniotomy
    Surgical procedure in which a bone flap that is removed for access to the brain is replaced at the end of surgery
  • Creatine kinase
    Muscle enzyme that is released from muscle cells in some forms of myopathy
  • Cryptogenic
    A condition in which a distinct lesion or pathogenesis is presumed, but has not been proven
  • d

  • Decerebellate rigidity
    Body posture characterized by rigid extension of the thoracic limbs, flexion of the pelvic limbs, and extension of the neck (opisthotonus); due to severe rostral cerebellar dysfunction
  • Decerebrate rigidity
    Body posture characterized by rigid extension of all four limbs and the neck (opisthotonus); due to severe midbrain dysfunction
  • Decussate
    To cross over
  • Delirium
    Abnormal mental status characterized by confusion, disorientation, fear, irritability, inattention and varying degree of consciousness
  • Dementia
    Sustained, acquired loss of memory and other intellectual capacities that impairs daily functioning
  • Demyelination
    Loss or destruction of the myelin sheath surrounding the axon; results in slowed nerve conduction
  • Dendrite
    Receiving portion of the neuron
  • Dermatome
    Cutaneous distribution of sensory innervation on the skin
  • Diaschisis
    Reduced metabolism or function of one region due to disease in an anatomically-distant, but connected, region due to disruption of afferent or efferent fibers
  • Diastematomyelia
    Rare malformation characterized by longitudinal splitting of the spinal cord by a septum
  • Diencephalon
    Rostral end of the brainstem consisting of the thalamus, hypothalamus, subthalamus, and epithalmus; anatomically a portion of the brainstem, but functionally more similar to the cerebrum
  • Diffuse axonal injury
    Widespread damage to white matter of the brain due to rotational shearing forces that occur with traumatic brain injury
  • Dorsal
    Of, on, or relating to the upper side or back of an animal, plant, or organ
  • Dorsal column
    Ascending tracts in the dorsal funiculus of the spinal cord carrying proprioceptive and tactile information to the brain
  • Dorsal horn
    Gray matter in the dorsal aspect of the spinal cord that receives sensory input from the body through the dorsal roots
  • Dorsal rhizotomy
    Surgical procedure in which the dorsal spinal nerve roots are transected to reduce spasticity or chronic pain
  • Drop metastases
    Metastatic tumors that spread from the primary tumor via the ventricular system to distant sites
  • Dura mater
    Thick, fibrous, outermost layer of meninges surrounding the brain and spinal cord
  • Dural tail sign
    Tail of contrast enhancement extending along the meninges away from the primary lesion; most commonly observed with meningioma, but can also be seen with lymphoma and other intradural tumors, as well as non-neoplastic inflammatory lesions
  • Dysesthesia
    Pain or discomfort from a stimulus (e.g., touch) that is normally non-painful
  • Dyskinesia
    Broad category of movement disorders characterized by excessive motor activity
  • Dysmetria
    Impaired rate and range of motion; tendency to overshoot or undershoot the target
  • Dysphagia
    Difficulty swallowing
  • Dysphonia
    Abnormal voice, often due to laryngeal muscle weakness such as that due to laryngeal paralysis, hypothryoidism, myasthenia gravis, etc.
  • Dysraphism
    Incomplete closure of a raphe; in neurology it is due to to neural tube closure defect
  • Dystonia
    Involuntary muscle spasms causing abnormal posture or body movements
  • e

  • Edinger-Westphal nucleus
    A nucleus of the oculomotor nerve (III) supplying pre-ganglionic parasympathetic fibers for pupillary constriction and lens accomondation
  • Efferent
    Motor pathways extending from the CNS to the periphery
  • Electroencephalogram
    Recording of electrical potentials arising from the cerebral cortex at the skin of the head
  • Electromyography
    Diagnostic tool in which spontaneous electrical potentials are recorded in sedated or anesthetized patients; there should be essentially no recordable activity in non-moving muscles, but spontaneous discharges may be detected in myopathic and neuropathic disorders. In human medicine, EMG is(...)
  • Encephalitis
    Inflammation or infection of the brain
  • Encephalocele
    Broad term to describe failure of bone fusion in the skull resulting in protrusion of meninges and/or brain parenchyma; strictly speaking, encephalocele is protrusion of the brain, while meningocele is protrusion of the meninges and meningoencephalocele is protrusion of both stuctures
  • Encephalopathy
    Any disorder of the brain
  • Endomysium
    Innermost layer of connective tissue around each individual muscle fiber
  • Enophthalmos
    Retraction of the eyeball back into the orbit
  • Ependyma
    Epithelial lining of the ventricles of the brain and central canal of the spinal cord
  • Ependymoma
    Primary CNS tumor arising from the ependymal cells of the ventricles or central canal
  • Epilepsy
    Any disorder characterized by chronic, repetitive, unprovoked seizures
  • Exophthalmos
    Protrusion of the eyeball
  • Extra-axial
    Lesion located within the skull or vertebral column, but outside the brain and spinal cord parenchyma
  • Extrapyramidal
    Motor fibers from the brain that do not pass through the pyramids
  • f

  • F-wave
    A long-latency compound muscle action potential observed after supramaximal stimulation of a nerve
  • Falcine herniation
    Displacement of the cingulate gyrus under the falx cerebri to the contralateral side, often secondary to increased intracranial pressure from a space-occupying mass
  • Falx cerebri
    Fold of dura mater between the two cerebral hemispheres
  • Fascicle
    Bundle of muscle (muscle fascicle) or nerve (nerve fascicle) surrounded by a layer of connective tissue (perimysium or perineurium)
  • Fasciculation
    Spontaneous axonal firing resulting in visible twitching of the muscle innervated; usually indicative of of deneration
  • Fibrillation
    Spontaneous electrical activity from a single muscle fiber not visible to the naked eye externally; observed during electromyography; indicative of a neuropathy or myopathy
  • Flaccid paralysis
    Severe form of hypotonia
  • Flocculus
    Small lobe of the cerebellum; involved in vestibular function
  • Fontanel
    Soft, membranous gap in the skull due to incomplete closure of cranial bone plates during development
  • Foramen magnum
    Large opening in the of the skull through which the spinal cord and vertebral arteries pass into the calavaria
  • Foramen of Luschka
    Lateral exits of CSF from the fourth ventricle to the subarachnoid space
  • Foramen of Magendie
    Midline exit of CSF from the fourth ventricle to the subarachnoid space
  • Foramen of Monro
    Connection between the lateral ventricles and third ventricle; also called the interventricular foramen
  • Forebrain
    Portion of the CNS arising from the prosencephalon containing the cerebral hemispheres and diencephalon
  • Fornix
    White matter structure that connects the hippocampus to the hypothalamus and septal nuclei
  • Fried egg artifact
    Perinuclear halo in oloigodendrocytes that are characteristic of oligodendrogliomas
  • Frontal lobe
    One of four major lobes of the cerebrum located rostral to the cruciate sulcus
  • g

  • Ganglion
    Collection of nerve cell bodies
  • Generalized seizure
    Seizure activity in both cerebral hemispheres simultaneously; clinically appears as bilateral motor activity and loss of consciousness; ANS signs may also be present (urination, salivation, etc.)
  • Genu
    Knee-like bend in the rostral end of the corpus callosum
  • Glia
    Supporting cells of the nervous system, including astrocytes, oligodendrocytes, microglia and ependymal cells
  • Gray matter
    Portion of the central nervous system containing neuronal cell bodies and dendrites
  • Guillain-Barre Syndrome
    An acute, inflammatory demyelinating polyneuropathy in man characterized by generalized lower motor neuron weakness, paresthesias, hyporeflexia, and labeled autonomic nervous system dysfunction. Thought to be due to autoimmune response triggered by a previous illness or recent vaccination.(...)
  • Gyrus
    A convoluted ridge on the outer surface of the cerebrum caused by infolding of the cerebral cortex and surrounded by sulci
  • h

  • Hemianesthesia
    Loss of sensation on one half of the body
  • Hemiparesis
    Weakness on one side of the body
  • Hemiplegia
    Paralysis on one side of the body
  • Hippocampal commissure
    Connects the hippocampus on each side
  • Hippocampus
    A c-shaped structure on the medial edge of the cerebral hemisphere; par of the limbic systemic involved in long-term memory and emotion
  • Hydranencephaly
    Congenital defect in which most of the cerebral hemispheres are replaced by sacs filled with cerebrospinal fluid
  • Hydrocephalus
    Increased size of ventricles and amount of cerebrospinal fluid in the brain
  • Hyperacusis
    Abnormally increased sensitivity to sound
  • Hyperpathia
    Excessive response to a painful stimulus
  • Hypertonicity
    Increased muscle tone
  • Hypotonicity
    Reduced muscle tone
  • i

  • Ictus
    Sudden attack, stroke, or seizure; in epileptology, it is the actual seizure in which chaotic electrical activity is present
  • Idiopathic
    Disorder without a known cause
  • Infarction
    Tissue damage or cellular death due to prolonged or severe ischemia or hemorrhage
  • Infundibulum
    Connection between the hypothalamus and pituitary gland containing the axons of hypothalamic neurons projecting to the posterior pituitary gland
  • Intention tremor
    A type of tremor whose severity worsens as the affected body part approaches the intended target, which may be missed; typically the result of cerebellar dysfunction
  • Internal capsule
    Broad band of white matter with afferent and efferent fibers to and from the cerebral cortex
  • Interneuron
    A neuron that receives input from one neuron and projects to another neuron, most commonly within the spinal cord
  • Intracranial pressure
    Pressure exerted by the brain, cerebrospinal fluid and cerebral blood within the calvaria
  • Intrathecal
    Space between the pia and arachnoid mater that contains cerebrospinal fluid
  • Ipsilateral
    Located on the same side of the body
  • j

  • Jacksonian seizure
    Seizure characterized by contiguous spread of electrical discharge through the cerebral cortex with corresponding spread of motor activity to contiguous anatomical areas; a.k.a., Jacksonian march
  • Jitter
    Measure of variability of potentials recorded from individual muscle fibers as by single fiber electromyography; increased variability occurs with myasthenia gravis
  • k

  • Ketogenic diet
    Diet that is high fat and low carbohydrate that is sometimes used to control seizures in specific types of epilepsy in humans
  • Kindling
    Process in which repeated subconvulsive stimulation, either electrically or chemically, permanently lowers the seizure threshold
  • l

  • Lacunar infarct
    Small infarction caused by occlusion of a single penetrating branch of a cerebral artery; most commonly observed in the thalamus in dogs and cats
  • Lambert-Eaton myasthenic syndrome
    Autoimmune disorder in which antibodies are directed against voltage-gated calcium channels in the presynaptic motor nerve that causes impaired release of acetylcholine and subsequent muscular weakness
  • Leptomeninges
    Combination of the pia and arachnoid mater
  • Leukodystrophy
    Group of white matter disorders characterized by white matter degeneration or abnormal growth/development of myelin
  • Limbic
    Subdivision of the nervous system that is important in emotion and memory; consists of the hippocampus, parahippocampal gyrus, cingulate gyrus, fornix, and multiple subcortical structures including portions of hypothalamus and thalamus
  • Lissencephaly
    A condition in which there is an absence of secondary sulci due to abnormal migration of cortical cells during development causing a smooth appearance to the surface of the cerebrum
  • Locus ceruleus
    Nucleus in the dorsal wall of the pons containing a large amount of melatonin; it is one of the main sources of norepinephrine in the brain and projects to many other regions of the nervous system and mediates arousal
  • Long tract signs
    Clinical signs referable to dysfunction of the corticospinal tract, spinothalamic tract, and dorsal columns/medial lemniscus
  • Lower motor neuron
    Neurons located in the brainstem or spinal cord that connect to muscle; dysfunction lesions to hypotonicity, loss of reflexes, and muscle atrophy
  • m

  • Medulloblastoma
    Primitive neuroepithelial tumor that often arises from the cerebellum
  • Meninges
    Three connective tissue membranes surrounding the brain and spina cord, including the pia, arachnoid and dura mater
  • Meningioma
    Tumor arising from the meninges
  • Meningitis
    Inflammation or infection of the meninges
  • Meningocele
    A form of spina bifida characterized by herniation of meninges through a defect in the dorsal arches
  • Meningomyelocele
    Congenital defect in which there is protrusion of the meninges and spinal cord tissue through an opening in the vertebrae due to incomplete fusion of the dorsal arches
  • Mesencephalon
  • Microglia
    Bone marrow-derived phagocytic glial cell involved in the immune response in the CNS
  • Miosis
    Pupillary constriction
  • Motor neurons
    Nerve cells that innervate and direct movement of muscles
  • Motor unit
    Motor neuron axon and the individual muscle fibers it innervates
  • Myasthenia gravis
    Disease of the neuromuscular junction due to autoantibodies directed against the nicotinic acetylcholine receptor (acquired myasthenia) or developmental lack of receptors (congenital myasthenia)
  • Mydriasis
    Pupillary dilation
  • Myelencephalon
    Medulla oblongata
  • Myelin
    Insulating sheath surrounding axons that speed nerve conduction velocity; made by oligodendrocytes in the CNS and Schwann cells in the PNS
  • Myelitis
    Inflammation or infection of the spinal cord
  • Myelogram
    Radiographic procedure in which contrast agent is injected into the subarachnoid space, thereby highlighting the edges of the spinal cord on post-injection radiographs
  • Myelopathy
    A disorder of the spinal cord
  • Myoclonus
    Sudden, shock-like contraction of muscle groups
  • Myokymia
    An involuntary, spontaneous, localized quivering of a few bundles within a muscle or a few muscle groups, but without sufficient force to move a joint
  • Myopathy
    A disorder of the muscles
  • Myotonia
    A muscle disorder characterized by abnormally prolonged muscle contraction due to delayed relaxation
  • n

  • Narcolepsy
    A disorder characterized by sudden sleep attacks; may also manifest as excessive daytime sleepiness and abnormal REM sleep
  • Neurogenic KCS
    A form of keratoconjunctivitis sicca ("dry eye") due to denervation of the lacrimal gland with disease or injury of the parasympathetic nucleus of the facial nerve, pterygopalatine ganglion, or the pre- or postglanglionic parasympathetic fibers that course with the facial nerve and then the(...)
  • Neuromuscular junction
    The synapse between a motor neuron and a muscle fiber
  • Neuropathy
    A disease of peripheral nerves
  • Neurotransmitter
    Chemical released from a nerve terminal that passes across the synapse to stimulate another neuron, muscle or effector organ
  • Nociception
    A sensory process in which nociceptors convert (transduce) a noxious stimulus (e.g., heat, cold, pressure, chemicals) causing tissue damage into an electrical signal carried by sensory neurons to the spinal cord and up to the brain. Nociception is necessary, but not sufficient for, a patient(...)
  • Non-communicating hydrocephalus
    Ventricular enlargement due to blockage of CSF flow from one ventricular system region to another, most commonly at the mesencephalic aqueduct
  • Notochord
    A flexible rod-like structure that helps organize nervous system development and aournd which the vertebral column forms; the nucleus pulposus of the intervertebral disks arises from the notochord
  • Nucleus
    A collection of neuronal cell bodies
  • Nystagmus
    Involuntary, rhythmic oscillation of the eyeballs
  • o

  • Obtunded
    Mild to moderate reduction in alertness
  • Oligodendrocytes
    A type of glial cell that is responsible for synthesis and maintenance of CNS myelin
  • Oligodendroglioma
    Primary CNS tumor originating from oligodendrocytes
  • Opening pressure
    Pressure obtained upon entering the subarachnoid space when performing a CSF tap
  • Ophthalmoplegia
    Paralysis of one or more extraocular muscles responsible for eyeball movement
  • Opisthotonus
    Extension of the head and neck, often the result of cerebellar dysfunction
  • Optic chiasm
    An x-shaped structure where axons of the optic nerves converge, partially cross over (65% cats, 75% dogs), and then diverge to become the optic tracts
  • Optic nerve
    Portion of the visual pathway containing axons of retinal ganglion cells passing from the retinas to the optic chiasm
  • Optic neuritis
    Inflammatory disease of the optic nerves
  • Optic radiations
    Portion of the visual pathway from the lateral genticulate nucleus in the thalamus to the primary visual cortex in the occipital lobe
  • Optic tract
    Portion of the visual pathway extended from the optic chiasm to the lateral geniculate nucleus of the thalamus
  • Orthotic
    Mechanical device, such as a brace or splint, that is designed to correct or compensate for abnormal limb movement
  • p

  • Palsy
    Paralysis of a muscle group
  • Paralysis
    Absence of motor function in a body part
  • Paraparesis
    Weakness in the pelvic limbs
  • Paraplegia
    Complete absence of voluntary movement in the hind limbs
  • Parasagittal
    Sagittal section that is lateral of midline
  • Paresthesia
    Skin sensation, such as burning, prickling, itching, or tingling, with no apparent physical cause
  • Partial seizure
    Seizure that occurs within a focal area of the forebrain; a.k.a., focal seizure
  • Penumbra
    The area surrounding the core of irreversibly damaged cells that has reduced electrical activity, but has preserved ionic homeostasis and is capable of recovery
  • Periaqueductal gray
    Gray matter surrounding the mesencephalic aqueduct in the midbrain
  • Perineurium
    Connective tissue sheath surrounding nerve fiber bundles
  • Peripheral nervous system
    Portion of the nervous system outside the brain and spinal cord consisting of the spinal nerve root, plexus, peripheral nerve, neuromuscular junction, and muscle
  • Photophobia
    Abnormal intolerance to light
  • Pia mater
    Innermost layer of meninges that is attached to the external surface of the brain and spinal cord
  • Pineal gland
    A body attached to the caudal third ventricle on midline; a major site of melatonin synthesis
  • Polymyositis
    Disorder characterized by inflammation or infection of multiple muscles
  • Pons
    The portion of the brainstem located between the midbrain and medulla
  • Porencephaly
    Cyst-like structure in the brain that is usually due to a destructive lesion or congenital malformation
  • Positive sharp wave
    Abnormal spontaneous muscle activity that may be observed during electromyography; characterized by an initial positive (downward) wave followed by a negative (upward) wave; can occur with myopathies and neuropathies
  • Prosencephalon
    The most rostral portion of the brain consisting of the cerebrum and diencephalon
  • Pupillary light response
    Constriction of the pupils in response to a bright light source
  • Pyramidal
    A subdivision of the motor system consisting of the descending tracts that pass through the pyramids, such as the corticospinal tract
  • q

  • Quadrigeminal bodies
    Two pairs of elevations on the dorsal surface of the midbrain, consisting of the rostral and caudal colliculi
  • r

  • Radiculoneuritis
    Inflammation or infection of spinal nerve roots
  • Radiculopathy
    Clinical signs associated with spinal nerve root compression
  • REM sleep behavior disorder
    A disorder in which there is incomplete or failure of muscle atonia that normally occurs in REM sleep causing abnormal movements during REM sleep; movements can be misinterpreted as seizure activity
  • Repetitive nerve conduction
    An electrodiagnostic test in which the compound muscle action potential is recorded from a muscle during a brief series of electrical stimulations of the motor nerve that innervates the muscle
  • Ring enhancement
    Peripheral contrast enhancement of a lesion, such as a glioma, metastatic tumor, or abscess
  • Rostral
    Toward the front of the brain
  • Rostral commissure
    One of three commissures connecting the cerebral hemispheres to each other; primarily connects the paleopallium on each side (olfactory bulbs, olfactory peduncles, piriform lobes and amygdaloid bodies)
  • s

  • Sagittal
    Vertical plane passing through the midline of a standing patient
  • Schizencephaly
    Congenital defect characterized by abnormal clefts extending from the cerebral cortex to the underlying ventricle
  • Schwann cell
    Glial cell that forms the myelin in the peripheral nervous system
  • Sella turcica
    Saddle-like prominence on the dorsal surface of the sphenoid bone that contains the pituitary gland
  • Sharp wave
    Transient EEG wave noted that appears as a positive deflection with a pointed peak lasting 70-200 milliseconds
  • Single fiber electromyography
    An electrodiagnostic test in which the action potentials are recorded from a single muscle fiber following stimulation of the motor nerve; normal muscle fibers have action potentials with little variability in latency; patients with myasthenia gravis have increased variability in onset of(...)
  • Somatosensory evoked potentials
    An electrodiagnostic test in which a series of electrical waves generated by neural structures along the somatosensory pathways are recorded following electrical stimulation of a peripheral nerve
  • Spike
    EEG pattern consisting of a pointed peak lasting less than 70 milliseconds; correlated with epilepsy
  • Spina bifida
    Congenital malformation in which the vertebral arches fail to close; can allow herniation of the meninges and/or spinal cord through the incompletely closed vertebral arches
  • Status epilepticus
    Continuous seizure activity longer than 30 minutes or two or more seizures without full recovery of consciousness between seizures
  • Strabismus
    Misalignment of the eyes
  • Stupor
    Condition of unresponsiveness in which the patient can only be aroused by a noxious stimulus
  • Subarachnoid space
    Space between the pia and arachnoid mater that contains cerebrospinal fluid
  • Subcortical
    Structures located immediately below the cerebral cortex, including the corona radiata, internal capsule, basal ganglia and thalamus
  • Sulcus
    Groove between two gyri
  • Suprasellar
    Structures located above the sella turcica
  • Suture
    Junction between two bones of the skull
  • Symptomatic epilepsy
    Epilepsy due to an identifiable cause, such as a brain tumor or encephalitis
  • Syncope
    Transient loss of consciousness due to lack of blood flow to the brain, often the result of a cardiac arrhythmia
  • Syringomyelia
    Central cavitation / fluid-filled structure within the spinal cord parenchyma
  • t

  • Tectum
    Dorsal aspect of the midbrain containing the rostral and caudal colliculi
  • Tegmentum
    Ventral aspect of the midbrain
  • Telencephalon
    Rostral portion of the prosencephalon consisting of the cerebral hemispheres
  • Tentorium cerebelli
    Fold of dura mater separating the occipital lobes and cerebellum
  • Tetany
    Sustained muscular contraction
  • Tetraparesis
    Weakness in all four limbs
  • Tetraplegia
    Paralysis of all four limbs
  • Titubation
    Tremor of the head and neck
  • Tolerance
    Gradual loss of response to a drug (e.g., oral diazepam) with chronic use
  • Tonic seizure
    Generalized seizure characterized by stiffening of the entire body
  • tonic-clonic seizure
    Generalized seizure characterized by initial extension of the limbs (tonic phase) followed by rhythmic muscle contractions (clonic phase); a.k.a., grand mal seizure
  • Tonsillar herniation
    Herniation of the cerebellar tonsils into the foramen magnum
  • Torticollis
    A form of dystonia characterized by head turn due to involuntary neck muscle contraction
  • Transient ischemic attack
    Transient neurological signs associated with a sudden reduction of blood flow to a particular region of the brain; signs last < 24 hrs; a.k.a., "mini stroke"
  • Transtentorial herniation
    Displacement of cerebral tissue (usually temporal or occipital lobe) under the tentorium cerebelli with compression of the brainstem (midbrain)
  • Transverse myelitis
    Inflammatory disorder affecting both sides of the spinal cord causing both motor and sensory deficits
  • Tremor
    Involuntary, rhythmic, alternating contraction of agonist and antagonist muscles
  • u

  • Upper motor neurons
    1st order neurons that originate in the brain and synapse on interneurons or lower motor neurons of the brainstem and spinal cord
  • v

  • Ventral
    Toward the bottom surface of a standing patient
  • Ventral horn
    Ventral portion of spinal cord gray matter containing motor neurons
  • Ventricles
    Four cerebrospinal fluid-filled cavities within the brain; consists of paired lateral ventricles, third ventricle, and fourth ventricle
  • Vermis
    Median region of the cerebellum
  • Vertigo
    A subjective sense that the external world is moving or spinning
  • Virchow-Robin space
    A perivascular space between an artery and vein and the pia mater
  • w

  • Wallerian degeneration
    Axonal and myelin degeneration that occurs distal to a site of injury
  • Watershed infarct
    An infarct that occurs in "border zones" of the brain that receive blood supply from two major arteries; requires inadequate blood flow from both arteries, most often the result of global hypoperfusion
  • White matter
    The part of the central nervous system containing axons
  • x

  • Xanthochromia
    Yellowish discoloration of the cerebrospinal fluid resulting from lysis of red blood cells following subacute to chronic subarachnoid hemorrhage
  • Xeromycteria
    Extreme dryness of the nasal passage, usually due to denervation of the lateral nasal gland, which is responsible for most of the moisture in the nose. The gland is innervated by parasympathetic fibers of the facial nerve.
  • Xerostomia
    Dry mouth due to decreased salivary secretion