Extrapyramidal motor signs in degenerative ataxias

Background: Extrapyramidal motor signs (EPS) are well-known symptoms of degenerative ataxia. However, little is known about frequency and appearance of EPS in subtypes of ataxia. Methods: We characterized 311 patients with ataxia clinically and genetically. Course of the disease and EPS were investigated according to a standardized protocol. Diagnostic and prognostic impact of EPS in subtypes of ataxia was analyzed by Kaplan-Meier plots. Results: Extrapyramidal motor signs occurred in all forms of ataxia, but frequency and type of EPS varied between genetically and clinically defined subtypes. Postural tremor in hereditary ataxias was typical for spinocerebellar ataxia type 2 (SCA2). Dystonia was generally rare in ataxias, but, if present, suggested SCA3. We observed a parkinsonian variant of SCA3 in which parkinsonism was present in the beginning of the disease and responded well to levodopa therapy, leading to diagnostic confusion. Parkinsonism in SCA3 was independent of CAG repeat length but ran in families, suggesting modifying genes. In idiopathic sporadic cerebellar ataxia (ISCA), EPS are more frequent in late-onset than in early-onset forms. In 50% of ISCA patients with parkinsonism, the diagnosis of multiple system atrophy remained questionable because of normal autonomic function. Conclusions: Extrapyramidal motor signs can help to predict the genetic subtype of ataxia. Extrapyramidal motor signs were more frequent in genetic subtypes in which basal ganglia affection has been demonstrated by post-mortem studies. However, no type of EPS was specific for an underlying mutation. In ISCA, EPS are an adverse prognostic factor. Parkinsonism is especially associated with a more rapid course of the disease.