Familial periodic ataxia.

Two members of a family suffer from recurrent attacks of either vertigo or cerebellar incoordination. The occurrence of these two distinct types of attack in the same patient may reconcile the disparate features of previously reported cases of familial periodic ataxia. The finding of downbeating nystagmus suggests a medullary disturbance. As in a previously reported family, the attacks were relieved by acetazolamide.