Striatal dopaminergic function in restless legs syndrome

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Abstract
Objective: To use PET to study striatal dopaminergic function in restless legs syndrome (RLS). Background: RLS is a common disorder experienced by as much as 5% of the population. It has been suggested that this condition is associated with a disturbance of dopaminergic transmission. Methods: The authors measured nigrostriatal terminal dopamine storage with 18F-dopa and striatal D2 receptor binding with 11C-raclopride PET in 13 RLS patients, five of whom were receiving treatment with l-dopa at the time of scanning. RLS results were compared with those of age-matched control subjects. Results: Mean caudate and putamen 18F-dopa uptake were mildly reduced in the RLS patients compared with control subjects, and this reached significance (p = 0.04) in the putamen. Mean D2 binding was reduced in the caudate (p = 0.01) and the putamen (p = 0.008) in RLS patients compared with control subjects. Six of the 13 RLS patients had caudate and putamen D2 binding reduced below the control range. Three other RLS patients showed only reduced putamen D2 binding. There were no significant differences in striatal 18F-dopa uptake or D2 binding between l-dopa–naive and l-dopa–treated RLS patients. Conclusions: These PET findings support the hypothesis of central dopaminergic dysfunction in RLS.