Spinocerebellar degeneration with negative electroretinogram: dysfunction of the bipolar cells.

We report the characteristics of three patients with spinocerebellar degeneration (SCD) with negative-type electroretinograms (ERGs). None of the patients showed retinal degeneration, but all had severe cerebellar ataxia, and brain MRIs showed cerebellar atrophy. Negative-type ERGs have been implicated in the selective functional impairment of the inner retinal layer, but few studies have reported dysfunction of the inner nuclear layer in SCD patients. Our subjects may be the first reported SCD cases with negative-type ERGs. Our results suggest that an etiologic relationship exists between cerebellar ataxia and negative-type ERGs. Further investigation of ERGs in patients with SCD could potentially lead to the identification of an increased number of SCD patients with negative-type ERGs and retinal pathogenesis.