Maculopathy and spinocerebellar ataxia type 1: a new association?

BACKGROUND: Autosomal dominant cerebellar ataxia is a rare heterogeneous group of diseases characterized by cerebellar symptoms, often associated with other multisystemic signs. Mild optic neuropathy has been associated with spinocerebellar ataxia type 1 (SCA1), but macular dysfunction has been reported in only 2 cases. We report the first family with SCA1 with several members affected by visual loss related to maculopathy.
METHODS: Cross-sectional clinical and electrophysiological study of a family with genetically confirmed SCA1. Patients with unexplained visual loss were included.
RESULTS: Four patients from the same family, carrying the same genetic mutation, were examined. Testing revealed an increased CAG trinucleotide repeat number within the SCA1 gene. Genetic testing results for SCA7 were negative. Visual acuities ranged between 20/20 and 20/200. Visual fields revealed central scotomas in most of the eyes, and funduscopy was unremarkable in most patients. Central retinal thinning of the retina or disorganized photoreceptor layers were found with optical coherence tomography (OCT). In one patient, multifocal electroretinography (mfERG) revealed central retinal dysfunction.
CONCLUSIONS: A clinically subtle or even occult maculopathy can occur in association with SCA1. Macular OCT and mfERG can be abnormal even in asymptomatic patients. Unexplained visual loss in SCA1 patients should prompt evaluation of macular function, even if clinical signs of maculopathy are absent.