Periodic vestibulocerebellar ataxia, an autosomal dominant ataxia with defective smooth pursuit, is genetically distinct from other autosomal dominant ataxias

Background: Periodic vestibulocerebellar ataxia is an autosomal dominant disorder characterized by defective smooth pursuit, gaze-evoked nystagmus, ataxia, and vertigo. The age of onset ranges from the third to the sixth decade. To date, all patients have originated from North Carolina, suggesting a single common founder. Objective: To clarify the classification of periodic vestibulocerebellar ataxia by determining whether it is allelic to other autosomal dominant cerebellar ataxias for which genes have been either localized or identified. Methods: Blood was collected and DNA isolated from 66 subjects (19 affected individuals) in two multigenerational families. The microsatellite markers used in the analysis either flanked or were tightly linked to the disease gene regions. Two-point and multipoint linkage analyses were performed to define the limits of exclusion. Results: Periodic vestibulocerebellar ataxia was excluded from loci linked to spinocerebellar ataxia type 1 (chromosome 6p), type 2 (chromosome 12q), type 3/Machado- Joseph disease (chromosome 14q), type 4 (chromosome 16q), and type 5 (11 cent) as well as to episodic ataxia with myokymia (chromosome 12p), episodic ataxia with nystagmus (chromosome 19p), acetazolamide-responsive hereditary paroxysmal cerebellar ataxia (chromosome 19p), and dentatorubral- pallidoluysian atrophy/Haw River syndrome (chromosome 12p). Conclusion: Periodic vestibulocerebellar ataxia is genetically distinct from those autosomal dominant ataxias for which chromosomal localization has been established.