Voxel-based morphometry in unmedicated patients with restless legs syndrome

BACKGROUND: The pathophysiology of restless legs syndrome (RLS) is not yet understood. A prior voxel-based morphometry (VBM) study reported gray matter increase in the pulvinar of the thalamus in a group of patients, most of whom were on medical treatment. Since there is evidence that medication can change the volume of cerebral structures, the question arises as to whether the reported morphometric alterations are caused by the RLS itself or, alternatively, are a consequence of drug treatment. To address this issue, we performed VBM in unmedicated RLS patients. METHODS: Fourteen patients with idiopathic RLS with no (n=11) or only minimal (n=3) treatment exposure in the past and 14 age- and sex-matched healthy subjects were investigated. All subjects were free of psychotropic drugs for at least 4 months. Morphological data were analyzed by using optimized VBM. RESULTS: We did not detect any structural changes except for slightly increased gray matter density in the ventral hippocampus (p=0.046 on the left and p=0.055 on the right side) and in the middle orbitofrontal gyrus (p=0.046 on the right and p=0.097 on the left side). CONCLUSION: Our study could not confirm the findings of a prior study. A possible explanation for the divergent findings is the difference between the populations examined. Since, in our study, essentially treatment-na?ve patients were investigated, it is possible that the prior findings reflect treatment-induced effects on cerebral morphology in RLS.