Spinocerebellar Ataxia Type 5

Spinocerebellar ataxia type 5 (SCA5) was originally described in an American family of Anglo-Saxon origin descending from the grandparents of President Abraham Lincoln. The genetic locus was assigned to chromosome 11. Subsequently, a second SCA family of French origin was identified with a similar clinical presentation in which the responsible gene is located in the same region. Initial symptoms consist of slowly progressive gait unsteadiness and dysarthria. The age of onset was 10 to 68 years (14 to 40) usually in the third decade. The ataxia is very slowly progressive and some patients remain ambulatory for well after 10 years. Examination shows evidence of a pancerebellar syndrome with intact or increased reflexes, normal plantar reflexes and normal sensory examination. Facial myokymia is a prominent feature among the French kindred. Nystagmus is less prominent than in SCA6 or SCA8. MRI shows a marked global cerebellar atrophy with sparing of the brainstem. The gene for SCA5 chromosome 11p11-q11 encodes a beta spectrin protein that is expressed in Purkinje cells.