Ocular motility in genetically defined autosomal dominant cerebellar ataxia

Abstract

Purpose: To describe ocular motility in patients having genetically characterized dominant cerebellar ataxia.

Design: Observational case series.

Method: Nine ataxic adults having the following molecular genetic diagnoses underwent ophthalmic examination and ocular motility recordings: four with spinocerebellar ataxia type 6 (SCA-6), three with SCA-3, one with SCA-1, and one with episodic ataxia type 2 (EA-2).

Results: Versions were normal in eight patients. Most were orthotropic, but one with SCA-3 had exotropia at near. The near point of convergence was remote in five patients. Eight of nine patients had horizontal nystagmus evoked by lateral gaze. All patients with SCA-6 had downbeat nystagmus. Downbeat nystagmus was absent in SCA-1, SCA-3, and EA-2. Three patients with SCA-6 and one with EA-2 had symptomatic improvement when treated with acetazolamide.

Conclusion: Patients with genetically defined dominant cerebellar ataxia generally had normal binocular alignment and versions and only mild vergence impairment. Downbeat nystagmus was strongly associated with the SCA-6 mutation, whose associated episodes of dizziness and imbalance may be relieved by acetazolamide.