Eye movements in a familial vestibulocerebellar disorder.

Eye movement abnormalities consisting of poor or absent smooth pursuit and vestibulo-ocular reflex suppression, gaze-paretic and rebound nystagmus, slow build-up of optokinetic nystagmus, mildly hyperactive vestibulo-ocular reflex, and a high incidence of strabismus were inherited in an autosomal dominant fashion in 10 members of a non-consanguineous English caucasian family. The onset was in early childhood, but was not congenital. In 7 cases there was no tremor, dizziness, consistent ataxia, or other cerebellar signs that are often associated with these ocular motor deficits, and apart from strabismus, patients were asymptomatic. Magnetic resonance imaging of the propositus was normal. After childhood there appears to be no progression, with the oldest affected member being 40 years. Two members had been prone to falling in childhood, and one admitted to dizziness when tired. This condition, which is probably benign, has not been previously described and may represent a very mild variant of episodic ataxia or a new vestibulocerebellar syndrome.