Neuroscience/Glossary

From PhysioWiki

Agraphesthesia

Inability to recognize characters drawn on skin.

Anisocoria

Left and right pupils are of different sizes. Usually caused by underlying normal physiology. Abrupt change in relative pupil size may be indicative of a motor neuron lesion.

Asynergia

Inability to perform find, coordinated movements in proper sequence.

Ataxia

Abnormality in the execution of movements, specifically regarding the rate, timing, and force of movements. A typical sign of cerebellar disease.

Bell's palsy

Characterized by hemiparalysis of the face, inability to dampen sounds in ipsilateral ear, functional loss of ipsilateral lacrimal gland. Results from a lower motor neuron lesion to the facial nerve.

Caloric testing

In a comatose individual, injecting cold water into inner ear causes eyes move towards that ear. Warm water causes eyes to deviate to the opposite side.

Cataplexy

Sudden loss of muscle tone triggered by strong emotions (e.g. anger, fear, surprise) felt during wakefulness.

Convergence

Necessary for near-field viewing. Accomplished by increasing the tone of the medial recti and decreasing the tone of the lateral recti. Convergence is mediated by the riMLF and requires a functioning oculomotor nerve (to innervate the medial rectus).

Diplopia

Double vision. Possibly due to unopposed extraocular muscles.

Dysarthria

Diminished ability to carry out motor functions of speech, frequently presenting as slurring, inappropriate phrasing, and lack of volume modulation.

Dysdiadochokinesia

Inability to perform rapid alternating movements.

Dysmetria

Inability to control the range of movements.

Dystonia

Muscular dysfunction due to simultaneous contraction of flexors and extensors.

Enophthalmos

Retraction of the orbit into the eye socket. Seen in Horner's syndrome.

Exophthalmos

Protrusion of the eyes, such as that seen in Graves' disease. Mentioned only for the sake of completeness.

Fasciculation

Small, spontaneous contractions of a muscle, especially after a muscle has been denervated (hence fasciculations are indicative of lower motor neuron lesions).

Horner's syndrome

Loss of sympathetic innervation to eye. Results in miosis (because of unopposed parasympathetic outflow from Edinger-Westphal nucleus), ptosis (because sympathetics partly innervate upper eyelid), and enophthalmos.

Hyperacusis

Increased acuity of sounds. Occurs with denervation of stapedius, such as from a CN VII lesion.

Hypnogogic hallucination

Dreams occurring during stage I sleep.

Hypotonia

Decreased muscle tone.

Intention tremor

Increasing tremor associated with voluntary movement.

Internuclear ophthalmoplegia

Lesion of the medial longitudinal fasciculus between the abducens and oculomotor nuclei. Results in ipsilateral loss of adduction during lateral gaze towards side opposite lesion. Vergence and vertical gaze are unaffected since these actions are controlled by the riMLF and oculomotor nuclei, which are both intact.

Lancinating pain

Acute, sharp pain that is often described as feeling like an electric shock.

Lissencephaly (classic)

Genetic disease resulting in incomplete migration of cells to the cortex. Signs include smooth cortex and widespread neuronal heterotopias (misplaced cells), resulting in mental retardation.

Miosis

Pupillary constriction. Can result from sympathetic lesion and consequent unopposed actions of parasympathetic fibers of pupillary constrictors.

Mydriasis

Pupillary dilation. Possibly due to parasympathetic deficits following lesioning/compression of the oculomotor nerve or of the Edinger-Westphal nucleus.

Narcolepsy

Abnormal tendency to enter REM sleep directly from the wakeful state.

Night terror disorder

Characterized by the acting out of dreams occurring in stage IV sleep, when there is least suppression of muscle activity.

Nystagmus

Smooth eye movements followed by a quick flick caused by a saccade.

One-and-a-half syndrome

Loss of ipsilateral abduction, contralateral adduction, and ipsilateral adduction during lateral gaze. Usually caused by lesion to ipsilateral abducens nucleus and medial longitudinal fasciculus.

Ptosis

Droopy eyelid. Possibly due to lesioning of the oculomotor nerve or sympathetic input to the eye.

Renshaw cell

Spinal cord interneuron that receives input from a lower motor neuron, sending inhibitory projections to the same motor neuron and also to interneurons that inhibit the motor neuron. Renshaw cells limit the activity of motor neurons.

Rinne test

CN VIII test in which tuning fork is placed sequentially over the mastoid process and external auditory canal. Normal individuals should experience better conduction through air than bone. If perception is opposite (bone better than air), then this is indicative of CN VIII problem.

Sleep paralysis

Inability to move for several seconds after awakening due to suppression of muscle tone by neurons near the locus coeruleus.

Strabismus

Lack of parallel tracking in the two eyes, resulting in diplopia. Usually caused by weakness in the muscles of one eye.

Tic douloureux

Characterized by episodes of severe pain localized to the areas innervated by V₂ or V₃ of CN V. Even slight stimuli can trigger an attack. Can be ameliorated surgically via spinal trigeminal tractotomy, in which the pars caudalis is lesioned. Recalling the secondary somatotopic map of the pars caudalis, one can see that a lesion at the caudalis-interpolaris border disrupts all protopathic information, while more caudal cuts will spare the perioral region, lips, nose, etc. ^{[190, 193]}

External links

• Sylvius glossary (comprehensive)