Sleep disturbance in spinocerebellar ataxias - Is the SCA3 mutation a cause of restless legs syndrome?

Objective: To identify and to characterize sleep disturbances in patients w ith hereditary ataxias. Background: We observed restless legs syndrome (RLS ) and impaired sleep as a frequent yet unrecognized symptom in spinocerebel lar ataxia type 3 (SCA3). Methods: A total of 89 patients with genetically defined subtypes of autosomal dominant cerebellar ataxias were investigated for sleep history and neurologic findings according to a standardized prot ocol. Nerve conduction studies were performed. Sleep was studied by overnig ht polysomnography in seven patients. Results: RLS was present in 45% of SC A3 patients but is rare in other types of autosomal dominant cerebellar ata xias. RLS was a frequent but not the only cause of sleep impairment in SCA3 . Impaired sleep in SCA3 is associated with older age, long-standing diseas e, and brainstem involvement. RLS tended to be more frequent in patients wi th clinical signs of polyneuropathy, but RLS was not restricted to patients with peripheral neuropathy. RLS was not observed in healthy members of SCA 3 families. Conclusions: RLS is a frequent and treatable cause of disabling sleep disturbance in SCA3. This study provides evidence for the expanded C AG repeat in the SCA3 gene as a molecular factor causing RLS.