PALLIDOTOMY IN PARKINSONS-DISEASE INCREASES SUPPLEMENTARY MOTOR AREA AND PREFRONTAL ACTIVATION DURING PERFORMANCE OF VOLITIONAL MOVEMENTS -AN (H2O)-O-15 PET STUDY

Supplementary motor area and right dorsal prefrontal cortex activation in Parkinson's disease is selectively impaired during volitional limb movements. Since posteroventral pallidotomy improves motor performanc e in Parkinson's disease patients 'off' medication (i.e. off medicatio n for 9-12 h), we hypothesized that it would also concomitantly increa se supplementary motor area and dorsal prefrontal cortex activation. S ix Parkinsons's disease patients with a median total motor Unified Par kinson's Disease Rating Scale (UPDRS) of 52.5 (range 34-66) 'off' medi cation underwent unilateral right posteroventral pallidotomy. The pati ents had (H2O)-O-15 PET when 'off' medication before and 3-4 months af ter surgery Each PET study comprised four to six measurements of regio nal cerebral blood flow either at rest or while performing regularly p aced joystick movements in freely selected directions (forward, backwa rd, left or right) using the left hand. Pre-and postoperative scans we re performed in an identical manner and the associated levels of activ ation were compared using statistical parametric mapping. After pallid otomy, the median total motor UPDRS score 'off' medication decreased b y 34.7 % (P = 0.03) and mean response times of joystick movements foll owing the pacing tones improved by 13.8% (P = 0.08). Relative increase s in activation of the supplementary motor area and right dorsal prefr ontal cortex were observed during joystick movements (P < 0.001). Decr eased activation was seen in the region of the right pallidum (P = 0.0 01). We conclude that pallidotomy reduces pallidal inhibition of thala mocortical circuits and reverses, at least partially, the impairment o f supplementary motor area and dorsal prefrontal cortex activation ass ociated with Parkinson's disease.