Intermittent unidirectional nystagmus.

A 38-year-old woman developed intermittent oscillopsia occurring every 45 to 90 minutes and lasting 20 to 40 seconds. She had a right-beating jerk nystagmus during these episodes. At other times, her neurologic examination was normal, and no nystagmus could be elicited. The nystagmus resolved when her classic migraine headaches were controlled with medical therapy. This intermittent unidirectional nystagmus may represent dormant periodic alternating nystagmus or another type of dormant nystagmus appearing intermittently due to episodic migrainous brainstem ischemia.