OCULOMOTOR PHENOTYPES IN AUTOSOMAL-DOMINANT ATAXIAS

Objective: To quantify the oculomotor features of the common spinocere bellar ataxia (SCA) syndromes. Setting: University ataxia clinic. Pati ents: Twenty probands with documented SCA mutations. Methods: Electro- oculographic recordings of saccadic, smooth pursuit, optokinetic, vest ibular, and visual-vestibular eye movements. Results: Distinct phenoty pe and genotype patterns were identified with modest overlap between p atterns. Slowing of saccade peak velocities occurred only in SCA1 and SCA2, being present in 100% of patients with SGA2, Impaired vestibule- ocular reflex gain occurred with SCA3 only. Patients with SCA6 had pro minent deficits in smooth tracking but normal saccade velocities and v estibuloocular reflex gain. Conclusions: The oculomotor findings are c onsistent with pure cerebellar involvement in SCA6, pontine involvemen t in SCA1 and SCA2, and vestibular nerve or nuclei involvement in SCA3 . These phenotypes can be useful for clinical diagnosis and for invest igating the mechanism of system Specificity with the SCA syndromes.