Electronystagmogram

Findings: Vestibulo-ocular responses * (VORs) are normal. Cold caloric** testing reveals a reduced amplitude of 30% on the right.

Impression: Right peripheral vestibular weakness.
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* VORs involve watching a light source move from side to side with the head fixed. Smooth pursuit is the function tested. A normal tracing looks like a smooth sine wave. Abnormal tracings are jerky.

** Cold calorics can be performed with either cold air or cold water. Cold applied to the tympanic membrane causes flow of endolymph in the horizontal canal, which in turn activates the hair cells in the ampulla. Because the stimulus is unilateral, the normal result is nystagmus. Electrical or video eye recordings measure the amplitude of nystagmus. The test is abnormal if there is a side-to-side difference of >20%.