Spinocerebellar ataxia

Spinocerebellar ataxia is not one disease but a family of progressive, inherited neurological disorders, with dozens of distinct genetic types now identified and roughly 150,000 people affected in the United States at any given time. The condition can be passed down in autosomal dominant, autosomal recessive or X-linked patterns depending on the type, and many of the dominant forms involve an expanded CAG repeat in the responsible gene that produces an abnormal, repeat-containing protein; in these forms the repeat can expand further across generations, causing symptoms to appear earlier and often more severely in children than in their affected parent. The defining feature is a slowly worsening loss of coordination affecting gait, hand movements, speech and eye control, accompanied over time by visible shrinkage of the cerebellum on imaging. Many people keep normal mental function throughout, though close to half of the known subtypes are also associated with cognitive decline. Diagnosis combines neurological examination, family history, MRI of the brain and spine, and increasingly targeted genetic testing that can now identify a specific subtype in many patients. There is no cure for any form of spinocerebellar ataxia; care focuses on physical and occupational therapy to preserve balance and function, speech therapy, and medications aimed at specific symptoms, while research into RNA-targeting and stem cell approaches continues.