Cognitive-predominant spinocerebellar ataxia type 8 with posterior cingulate cortex hypoperfusion mimicking early-onset Alzheimer's disease: A case report.

Spinocerebellar ataxia type 8 (SCA8) is an autosomal dominant neurodegenerative disorder caused by CTG/CAG repeat expansion in ATXN8OS/ATXN8 genes. The primary clinical feature is cerebellar ataxia, but approximately 30% of patients present with cognitive impairment, characterized by attentional disturbances and executive dysfunction. These cognitive deficits remain poorly understood, and no functional neuroimaging studies have been reported. We report a case of SCA8 presenting predominantly with cognitive impairment and showing marked hypoperfusion in the posterior cingulate cortex (PCC) on N-isopropyl-p-[123I]-iodoamphetamine single-photon emission computed tomography, closely resembling early-onset Alzheimer's disease. This case suggests PCC dysfunction may contribute to cognitive decline in SCA8.