Motor fluctuations and levodopa-induced peak dose dyskinesias in parkinsonism due to spinocerebellar ataxia type 3

Spinocerebellar ataxia (SCA) type 3 is often reported as a cause of familial parkinsonism, and may present as a relatively “pure” parkinsonian phenotype, indistinguishable in its clinical features and responsiveness to levodopa from idiopathic Parkinson’s disease (PD). In contrast to PD, levodopa induced dyskinesias and motor fluctuations are not common in atypical parkinsonian syndromes. We report a patient who presented with the ataxic phenotype of SCA3, and then developed progressively worsening levodopa-responsive parkinsonism over nine years’ follow up. High dose levodopa therapy led to the onset of peak-dose choreiform dyskinesias and wearing-off of levodopa effect, findings not previously associated with the ataxic phenotype of SCA3. The pathogenesis of parkinsonism in SCA3 and the possible mechanisms leading to peak-dose dyskinesias are discussed. Genetic testing for SCA may be performed more liberally in patients with otherwise “typical” PD, particularly in the face of a positive family history.