Spinocerebellar ataxia type 1, 2, and 3 and restless legs syndrome: Striatal dopamine D2 receptor status investigated by [C-11]raclopride positron emission tomography

In spinocerebellar ataxias (SCAs), up to 30% of patients complain of restless legs syndrome (RLS). In primary RLS. a putative role of the dopaminergic system has been postulated. To assess dopaminergic function in SCA 1, 2, and 3, dopamine D-2 receptor binding potential (BP) was assessed by [C-11]raclopride positron emission tomography in 10 SCA patients. 4 of whom suffered from RLS as demonstrated by poly somnography. BP was compared to 9 age-matched control subjects. In 2 SCA patients, striatal BP was clearly reduced (<2 SD below the mean of controls). However, there were no significant group differences between SCA and controls, largely owing to a significantly higher variance of striatal BP in SCA. BP was negatively correlated with disease duration. The fit suggests an increased BP in early stages, followed by a moderate decline in all quantified regions (caudate, dorsal putamen, ventral striatum) presumably reflecting a progressive loss of D-2 receptors. RLS in SCA was not accompanied by a significant reduction of D-2 receptor availability in the striatum. This missing correlation may point to an extrastriatal origin of RLS. (C) 2006 Movement Disorder Society.