Spinocerebellar Ataxia Type 18

Spinocerebellar ataxia type 18 (SCA18) is a very rare subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term). It is characterized by sensory neuropathy and cerebellar ataxia.

Epidemiology

Prevalence is unknown. Only 26 cases in a 5-generation American family of Irish ancestry have been reported to date.

Clinical description

Onset is in the 2nd and 3rd decades of life with symptomatic onset ranging from 13 to 27 years. Patients initially present with axonal sensory neuropathy, while cerebellar ataxia and motor neuron dysfunction develop later.

Etiology

SCA18 has been linked to chromosome 7q22-q23 but the responsible gene mutation has not yet been identified. Both SCA3 and SCA4 are also associated with a peripheral neuropathy and should be taken into account in the differential diagnosis.

Prognosis

Prognosis is unclear. However, mean disease duration from age at onset of illness to age at last examination is about 24 years in the reported cases.