Ocular motility in genetically defined autosomal dominant cerebellar ataxia.

Abstract

To describe ocular motility in patients having genetically characterized dominant cerebellar ataxia. Observational case series. 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). 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. 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.