Role of the dopaminergic system in chronic pain - a fluorodopa-PET study

Recent data fi um animal experiments suggest an important role for the basa l ganglia in the processing and sensorimotor gating of nociceptive informat ion, However, very little is known about their possible participation in hu man pain. Because of our previous finding of increased excitability of the blink reflex (a brainstem reflex under dopaminergic inhibitory control) in some burning mouth syndrome (BMS) patients, we have studied the dopaminergi c function of the striatum putamen and caudatus) of EMS patients with posit ion emission tomography (PET). 6-[F-18]]fluorodopa (FDOPA) PET scans were d one on ten EMS patients and 14 healthy control subjects. The presynaptic do paminergic Function was significantly decreased in the right putamen (20%, P = 0.04) of the EMS patients compared to control subjects. On the left sid e, the FDOPA uptake was decreased by 17% (P = 0.08). The mean FDOPA uptake was not significantly changed in the caudate nucleus of the patients. The f inding of decreased striatal FDOPA uptake in the putamen supports our previ ous neurophysiological observations indicating decreased dopaminergic inhib ition in EMS patients. The present result provides direct evidence of the i nvolvement of the nigrostriatal dopaminergic system in pain for the first t ime in a clinical pain condition. (C) 2001 International Association For th e Study of Pain. Published by Elsevier Science B.V. All rights reserved.