Recent data from animal experiments suggest an important role for the basal ganglia in the processing and sensorimotor gating of nociceptive information. However, very little is known about their possible participation in human 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 dopaminergic function of the striatum (putamen and caudatus) of BMS patients with positron emission tomography (PET). 6-[18F]fluorodopa (FDOPA) PET scans were done on ten BMS patients and 14 healthy control subjects. The presynaptic dopaminergic function was significantly decreased in the right putamen (20%, P=0.04) of the BMS patients compared to control subjects. On the left side, 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 finding of decreased striatal FDOPA uptake in the putamen supports our previous neurophysiological observations indicating decreased dopaminergic inhibition in BMS patients. The present result provides direct evidence of the involvement of the nigrostriatal dopaminergic system in pain for the first time in a clinical pain condition.
aDepartment of Clinical Neurophysiology, Turku University Central Hospital, PL 52, FI-20 521 Turku, Finland
bTurku PET Centre, Turku University Central Hospital, Turku, Finland
cDepartment of Oral Diseases, Turku University Central Hospital, Turku, Finland
dDepartment of Neurology, Turku University Central Hospital, Turku, Finland
eDepartment of Radiology, Turku University Central Hospital, Turku, Finland
fTurku PET Centre, Radiopharmaceutical Chemistry Laboratory, MediCity PET and Accelerator Laboratory, Turku, Finland
*Corresponding author. Tel.: +358-2-261-1939; fax: +358-2-261-3922
Received 27 March 2000; received in revised form accepted August 9 and 2000.