Maculopathy And Spinocerebellar Ataxia Type I: A New Association?

Abstract

Purpose: : Autosomal Dominant Cerebellar Ataxia is a rare heterogeneous group characterized by cerebellar symptoms, often associated with other multisystemic signs. Mild optic neuropathy has been associated with SpinoCerebellar Ataxia type 1 (SCA1), whereas macular dysfunction has been reported only twice, in single cases. We report the first family with several members affected by visual loss related to a maculopathy associated with a genetically identified SCA1.

Methods: : Cross-sectional clinical and electrophysiological study of a family with genetically confirmed SCA1. Patients with unexplained visual loss, but also asymptomatic members of the family were included.

Results: : Four patients of the same family were explored. Genetic testing revealed an increased CAG trinucleotide repeat number within the SCA1 gene, confirming the diagnosis of SCA1. Genetic testing results for SCA7 were negative. Visual acuities ranged between 20/200 to 20/20. Visual fields revealed central scotomas in most explored eyes. Fundus examination was considered within normal limits in most of the patients, disclosing only in few eyes slight foveolar pigmentary alterations. Central retinal thinning or disorganized photoreceptor layer were identified with Optical Coherent Tomography. Retinal nerve fiber layer (RNFL) measurements were normal, or slightly decreased temporally. Full electrophysiological examination has been completed in one patient. Multifocal Electroretinogram (mERG) revealed central damages, whereas global ERG was normal. Visual Evoked Potentials (VEP) were abnormal, related to the foveal dysfunction.

Conclusions: : A clinically occult maculopathy can occur in association with SCA1. In most cases the clinical ophthalmoscopic findings were very subtle, but confirmed by macular OCT and multifocal ERG, even in asymptomatic patients. Further studies are required to establish the frequency of macular involvement in SCA1.

Keywords: visual impairment: neuro-ophthalmological disease • retinal degenerations: hereditary • neuro-ophthalmology: optic nerve