Ocular motility in North Carolina autosomal dominant ataxia

The term "vestibulocerebellar ataxia" has been applied to a rare, autosomal dominant, late-onset disease with unusual ocular motility findings. We examined the ocular motility of 18 family members from two different kindreds and found 11 affected individuals. Both families in the present study, one of which was originally described by Farmer and Mustian, as well as the family reported by Farris et al., originated from Johnston County, North Carolina. We suspect that all three of these families have a common ancestral origin. The age of onset of the disorder was 31-60 years in the individuals examined. Ataxia, vertigo, diplopia, oscillopsia, and tinnitus were common complaints. Although a variety of eye movement abnormalities have previously been described in this disease, the most prominent and consistent findings in our patients were (a) abnormal smooth pursuits, (b) inability to suppress the vestibuloocular reflex (VOR), and (c) gaze-evoked nystagmus. These findings suggest that the cerebellar flocculus may be the primary site of pathology.