Cyclic vertigo with predictable recurrence.

The long-term follow-up of six children with "cyclic vertigo," that has recurred for years, at strikingly predictable intervals, is presented. Vertigo and photophobia, lasting several hours, start early in the morning, daily for several consecutive days, and recur at predictable intervals without evidence of long-term neurological deficits. The interval between events increases with age. Diagnostic criteria are suggested. Cyclic vertigo may be a migraine equivalent caused by periodic derangement of the mechanisms controlling the generation of circadian rhythms.