Natural History of Spinocerebellar Ataxia Type 7 (SCA7)

National Eye Institute

Investigators

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Abstract

Spinocerebellar Ataxia Type 7 is a neurodegenerative disease caused by an expansion of a CAG trinucleotide repeat in the coding region of the ATXN7 gene. It is distinguished from other autosomal dominant spinocerebellar ataxias by its associated retinal degeneration. Vision loss is therefore a significant comorbidity affecting the quality of life of these patients however at this time, treatment is limited to lifestyle modification. The eye presents itself as an excellent target for research on potential therapies as it is relatively immune privileged, surgically accessible and easily examined and imaged. Establishing proof-of-concept for a therapy in ocular disease is therefore very attractive in SCA7 before application in other CNS systems. While numerous case reports or small case series have been reported in populations from across the globe, the longitudinal clinical course of retinal degeneration in molecularly-confirmed SCA7 individuals has not yet been documented. With this study, we hope to gather this information in anticipation of future clinical trials. 19 patients have successfully completed their baseline evaluations, including standardized medical/ophthalmic history, complete baseline eye examination as well as color vision testing, visual field testing, electroretinography, psychophysiology, ophthalmic imaging and eye movement recordings, neurology exam, neuroimaging, eye movement recordings and neuropsychological assessment if able to participate. Age ranging from 15.6 to 62.8 years enrolled with a range of 40 to 69 expanded CAG repeats (normal <18) and different levels of disease severity. Best corrected visual acuity has ranged from 20/16 to 20/400, with R=0.97, p<0.0001 correlation of acuity between eyes of a given participant. Optic atrophy and cone rod dystrophy were seen to varying degrees. As patients continue to enroll and return for follow up visits, we hope to complete further longitudinal analysis and potentially identify clinical outcome measures for future trials.