REPETITIVE PAROXYSMAL NYSTAGMUS AND VERTIGO

A 55-year-old woman had paroxysms of vertigo and visual blurring assoc iated with complex combined torsional, horizontal, and vertical nystag mus. These episodes occurred regularly at 2-minute intervals, each att ack lasting for 15 seconds. Between attacks, there was a much finer as ymptomatic nystagmus whose components were in the opposite direction t o those associated with the paroxysmal attacks. A brain MRI revealed a n arteriovenous malformation in close proximity to the left vestibular nucleus, with evidence of previous bleeding. Caloric testing demonstr ated a left-sided vestibular paresis. We suggest that neurons in this patient's damaged left vestibular nucleus are usually underactive but regularly produce pathologic brief bursts of hyperactivity causing epi sodic reversal and gross exacerbation of her resting nystagmus. Treatm ent with low-dose carbamazepine was successful in abolishing both the paroxysms of nystagmus and the symptoms of vertigo and visual disturba nce.