Nystagmus is a constant, spontaneous, cyclical movement of the eyeball.

Pathologic nystagmus is seen in bilateral amblyopia, labyrinthine irritation, and neurologic diseases. This condition may be due to lesions of the vestibular nuclei, such as occur in multiple sclerosis (see Diagnostic Code: 8018 Multiple sclerosis), labyrinthitis, encephalitis, or syringobulbia. Normal physiologic nystagmus may be caused by end-horizontal gaze, by repetitive visual stimulation, or by caloric stimulation.

Endolymph flow in the semicircular canals inputs (sends messages) to the vestibular nuclei (in the brainstem). Vestibular nystagmus is always of the jerk type, which is usually characterized by a slow drift from the target followed by a fast corrective involuntary movement (saccades). This nystagmic eye movement is usually horizontal (left or right), but may be upbeat (increased on upward gaze), or downbeat (nystagmus on downgaze), vertical, oblique, or a combination of the movements. Some additional signs that may occur are: reduction of visual acuity, head tilting, and past-pointing.

Tests that may be used include: electronystagmography; irrigating the ears with alternating hot and cold water (caloric stimulation); electromyography of the eye muscles; slit lamp examination; and ophthalmoscopy.

Treating the underlying diseases causing nystagmus may relieve the condition. Periodic alternating nystagmus has reportedly been abolished by the use of skeletal central acting muscle relaxants. Acquired pendular nystagmus may improve with the administration of some anticonvulsant medications.

Nystagmus is usually noticeable and cosmetically disturbing.

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