The role of opioids in restless legs syndrome: an [11C]diprenorphine PET study

Opioids have been shown to provide symptomatic relief from dysaesthesias and motor symptoms in restless legs syndrome (RLS). However, the mechanisms by which endogenous opioids contribute to the pathophysiology of RLS remain unknown. We have studied opioid receptor availability in 15 patients with primary RLS and 12 agematched healthy volunteers using PET and [ 11 C]diprenorphine, a non-selective opioid receptor radioligand. Ligand binding was quantified by generating parametric images of volume of distribution (V d) using a plasmaderived input function. Statistical parametric mapping (SPM) was used to localize mean group differences between patients and controls and to correlate ligand binding with clinical scores of disease severity