positional nystagmus

nystagmus /nys·tag·mus/ (nis-tag´mus) involuntary rapid movement (horizontal, vertical, rotatory, or mixed, i.e., of two types) of the eyeball.nystag´mic

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aural nystagmus  vestibular n.

caloric nystagmus  rotatory nystagmus induced by irrigating the ears with warm or cold water or air; see caloric test, under test.

Cheyne's nystagmus , Cheyne-Stokes nystagmus a peculiar rhythmical eye movement.

dissociated nystagmus  that in which the movements in the two eyes are dissimilar.

end-position nystagmus  that occurring in normal individuals only at extremes of gaze.

fixation nystagmus  that occurring only on gazing fixedly at an object.

gaze nystagmus  nystagmus made apparent by looking to the right or to the left.

gaze paretic nystagmus  a form of gaze nystagmus seen in patients recovering from central nervous system lesions; the eyes fail to stay fixed to the affected side with a cerebral or pontine lesion.

labyrinthine nystagmus  vestibular n.

latent nystagmus  that occurring only when one eye is covered.

lateral nystagmus  involuntary horizontal movement of the eyes.

opticokinetic nystagmus , optokinetic nystagmus the normal nystagmus occurring when looking at objects passing across the field of vision, as in viewing from a moving vehicle.

pendular nystagmus  that which consists of to-and-fro movements of equal velocity.

positional nystagmus  that which occurs, or is altered in form or intensity, on assumption of certain positions of the head.

retraction nystagmus , nystagmus retracto´rius a spasmodic backward movement of the eyeball occurring on attempts to move the eye; a sign of midbrain disease.

rotatory nystagmus  involuntary rotation of eyes about the visual axis.

spontaneous nystagmus  that occurring without specific stimulation of the vestibular system.

undulatory nystagmus  pendular n.

vertical nystagmus  involuntary up-and-down movement of the eyes.

vestibular nystagmus  that due to disturbance of the vestibular system; eye movements are rhythmic, with slow and fast components.

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positional nystagmus

n.

A nystagmus occurring only when the head is in a particular position.

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nystagmus

a periodic, rhythmic, involuntary movement of both eyeballs in unison. There is a slow component in one direction and a quick return. The movement may be vertical, horizontal or rotary. Common causes are lesions of the cerebellum or the vestibular apparatus, or increased intracranial pressure.

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aural nystagmus

labyrinthine nystagmus.

cerebellar nystagmus

one characterized by tremor, without fast and slow components.

Cheyne's nystagmus

a peculiar rhythmical eye movement resembling Cheyne-Stokes respiration in rhythm.

congenital nystagmus

may be a primary functional defect or secondary to lesions in the visual pathways, sometimes associated with albinism. Reported in cattle, cats (particularly Siamese), and dogs.

dissociated nystagmus

that in which the movements in the two eyes are dissimilar.

gaze nystagmus

nystagmus made apparent by looking to the right or to the left.

horizontal nystagmus

that in which the eyes move from side to side with the fast component opposite to the side of the lesion; seen with central or unilateral peripheral vestibular disease.

jerk nystagmus

vestibular nystagmus (see below).

labyrinthine nystagmus

vestibular nystagmus due to labyrinthine disturbance.

latent nystagmus

that occurring only when one eye is covered.

lateral nystagmus

involuntary horizontal movement of the eyes.

ocular nystagmus

wandering movement of the eyes as though searching for something. Associated with congenital blindness.

optokinetic nystagmus

nystagmus induced by looking at objects moving across the field of vision.

oscillatory nystagmus

pendular nystagmus.

pendular nystagmus

that which consists of to-and-fro movements of equal velocity.

positional nystagmus

that which occurs, or is altered in form or intensity, on assumption of certain positions of the head.

postrotatory nystagmus

a normal finding after the animal has been rotated, with the fast phase away from the direction of rotation.

resting nystagmus

that occurring while the head is stationary.

retraction nystagmus, nystagmus retractorius

a spasmodic backward movement of the eyeball occurring on attempts to move the eye; a sign of midbrain disease.

rotatory nystagmus

involuntary rotation of the eyes about the visual axis.

spontaneous nystagmus

that occurring without specific stimulation of the vestibular system.

vertical nystagmus

involuntary up-and-down movement of the eyes.

vestibular nystagmus

nystagmus due to disturbance of the labyrinth or of the vestibular nuclei; the movements are usually jerky.

undulatory nystagmus

an inherited disorder of Finnish Ayrshire cattle; there is a synchronous, tremor-like movement of the eyes but affected aninals are otherwise healthy.

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positional

pertaining to position or posture.

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positional nystagmus

see positional nystagmus.