Vestibular dysfunction in hereditary ataxia.

A kindred with a unique autosomal dominantly inherited ataxia of late onset is described. Manifestations of the condition include defective optokinetic nystagmus and absent or abnormal oculo-vestibular responses, in association with normal cochlear function. It is possible that these latter features may serve as "markers" to indicate the presence of the disease in presymptomatic young adults, thereby facilitating important genetic counseling.