2019 Volume 78 Issue 2 Pages 55-60
Spinocerebellar degeneration (SCD) is a group of neurodegenerative disorders with cerebellar ataxia as the cardinal clinical sign. Among the types of SCD, spinocerebellar ataxia type 6 (SCA6) shows characteristic neuro-otological signs and symptoms distinct from other types of SCD. The characteristic features include gaze-evoked nystagmus, usually in the horizontal direction, vertigo or oscillopsia, and downbeat positioning nystagmus, which can be observed when the patient's position is quickly changed from the sitting to the supine position. The underlying genetic abnormality in SCA6 is an expansion of trinucleotide CAG repeats in the α1A-calcium channel gene, which is most abundantly expressed in the cerebellar Purkinje cells. Observation of the characteristic nystagmus and documentation of vertigo or oscillopsia in patients with ataxia suggests the possibility of SCA6.
