D2 receptor binding in dopa-responsive dystonia

We have studied dopamine D₂ receptor binding by [¹¹C]raclopride positron emission tomography in 14 patients with dopa-responsive dystonia (DRD). Data were compared with 16 levodopa-treated patients with Parkinson's disease (PD) and 26 healthy controls. The results revealed an elevated [¹¹C]raclopride binding index in the putamen and caudate nucleus of DRD patients compared with controls as well as significant elevation in the caudate nucleus compared with PD patients. The increase of [¹¹C]raclopride binding may be interpreted either as reduced tracer displacement by endogenous dopamine, or as an alteration of the receptor features due to chronic dopamine deficiency. The difference in [¹¹C]raclopride binding in DRD and PD patients in the caudate nucleus suggests that this structure may be of pathophysiological relevance in the presentation of the clinical features of both diseases.