Nystagmus

Background

• Nystagmus = involuntary eye movement
• The semicircular canals of the vestibules and the extraocular muscles of the eye function together physiologically to help control gaze locked when the head is in motion
• Nystagmus is an aberration in this stabilization of the ocular muscles when in motion

Clinical Features

• Rapid, uncontrolled, rhythmic oscillation of the eye
• May be horizontal, vertical, and/or rotary

Differential Diagnosis

Congenital Nystagmus

• Optic nerve hypoplasia
• Macular disease
• Noonan syndrome

Acquired Nystagmus

• Head trauma, tympanic membrane rupture
• Brain tumor
• Stroke
• Chiari malformation
• Meniere's disease, BPPV, labyrinthitis, Vestibular Neuritis
• Multiple sclerosis
• Wernicke–Korsakoff syndrome, thiamine deficiency
• Tox causes:
  • Alcohol intoxication, benzodiazepines, barbiturates, GHB
• Ketamine, Phencyclidine
• Amphetamines, MDMA
• Marijuana
• Lithium
• Phenytoin, fosphenytoin, carbamazepine, oxcarbazepine, lacosamide, gabapentin
• Salicylates, NSAID toxicity

Evaluation

• Differentiate monocular vs. binocular
  • Monocular suggests medial pontine stroke or medial longitudinal fasciculus damage
  • Look for contralateral internuclear opthalmoplegia (INO)
• Differentiate between central versus peripheral lesions

Central	Peripheral
Pure vertical, pendular, or rotary	Horizontal
Fast beat towards lesions	Fast beat away from lesion
Not relieved by gaze fixation	Relieved by gaze fixation
Cerebellar signs	No cerebellar signs

Optokinetic Drum Test

• Optokinetic reflex develops ~6 months of age
• Slow pursuit of eyes towards direction of vertical bar movement with quick saccade towards the opposite side to find the next bar to fixate on
• Abnormal in congenital nystagmus
• In parietal or parietal-occipital lesions, optokinetic nystagmus is impaired when the drum is rotated towards side of lesion
  • See OKN drum to the right
  • See OKN drum to the left

"H in space" Test

• Trace H in space

Caloric Reflex Test (also known as Vestibular Caloric Stimulation)

• The best clinical test for the Vestibulo-Optic reflex
• Water irrigated into the external auditory canal will exaggerate nystagmus if present
• Temperature of the irrigated water will control the direction.
  • Cold water will exaggerate a nystagmus to move contralaterally
  • Warm water will exaggerate a nystagmus to move ipsilaterally

COWS: Cold Opposite, Warm Same.

Management

Stabilize patient and manage primary cause of illness.

See Also

• Focal neurologic deficits

References

Authors

HE KDMC, Kevin Lu, Claire, Ross Donaldson, Michael Holtz