Neuro-ophthalmologic features of spinocerebellar ataxia type 7

Spinocerebellar ataxia type 7 (SCA7) is a progressive ataxia that is unique among inherited ataxias in having a high prevalence of retinal photoreceptor abnormalities. However, the ophthalmic features and their relationship to the neurologic features of SCA7 have not been widely reported. The goal of this study was to provide increased documentation.

The medical records of 10 consecutive patients with SCA7 examined in the Neuro-Ophthalmology Clinic at Kresge Eye Institute between 2000 and 2008 were reviewed retrospectively. Each patient underwent a standardized ophthalmologic and neurologic examination. Some patients also underwent electroretinography (ERG). Eight patients had genetically confirmed disease and 2 patients had presumptive SCA7 based on their clinical presentation. Patients were excluded if they had visual loss or ataxia due to other causes.

Nine patients reported visual symptoms at presentation, including hemeralopia, photophobia, dyschromatopsia, and blurred vision. In 3 of these patients, the visual symptoms had preceded the onset of ataxic symptoms. Visual acuity was abnormal in all patients at presentation. Four patients with visual dysfunction had normal or minimally abnormal macular pigmentary changes, but all patients had abnormal electroretinograms (ERGs) showing primarily cone dysfunction. The severity of visual loss and the severity of ataxia were frequently discordant.

Based on this study, patients with SCA7 often have visual symptoms that may precede, accompany, or follow the onset of ataxic symptoms. The severity of vision loss and ataxia may be discordant. Ophthalmoscopic evidence of macular abnormalities may be scant, but results of ERG will always be abnormal. This information may assist in earlier and more cost-effective diagnosis and permit more effective patient counseling.