Spinocerebellar Ataxia-Type 17
Spinocerebellar ataxia-type 17 (SCA17) is an autosomal dominant cerebellar ataxia with a complex and variable phenotype characterized by ataxia, dementia, chorea, dystonia, and parkinsonism. Affected patients typically present in early or middle adulthood (mean age 33 years) with progressive gait and limb ataxia which is usually accompanied by dementia, psychiatric symptoms, and variable extrapyramidal features. Additional symptoms and signs such as hyperreflexia, saccadic slowing, akinesia, mutism, and seizures may develop, reflecting widespread cerebral and cerebellar involvement. The diagnosis of SCA17 relies on genetic testing to detect an abnormal CAA/CAG repeat expansion in TATA-binding protein (TBP), the only gene abnormality known to be associated with SCA17.
KeywordsPsychiatric Symptom Repeat Expansion Gene Abnormality Additional Symptom Gait Ataxia
Clip 1: examination exhibits only reduced left arm swing. Gait appears normal, although subjectively he finds it more difficult to perform tandem gait than 2 years previously. Clip 2: another patient with SCA17 shows mild finger-nose ataxia on the right side and dysarthric, scanning speech. Gait is ataxic requiring use of a walker. (Video contribution from Dr. Susan Perlman, Department of Neurology at David Geffen School of Medicine at UCLA.)
SCA type 17.mp4 (MP4 9,957KB)