REGIONAL METABOLIC CORRELATES OF SURGICAL OUTCOME FOLLOWING UNILATERAL PALLIDOTOMY FOR PARKINSONS-DISEASE

Stereotaxic ventral pallidotomy has been employed in the symptomatic t reatment of patients with advanced Parkinson's disease (PD). To unders tand the pathophysiology of clinical outcome following this procedure, we studied 10 PD patients (5 men and 5 women; mean age, 60.0 +/- 6.1 years; mean Hoehn and Yahr stage, 3.8 +/- 1.0) with quantitative F-18- fluorodeoxyglucose (FDG) and positron emission tomography (PET). All p atients were scanned preoperatively; 8 of 10 patients were rescanned 6 to 8 months following surgery. Clinical performance was assessed off medications before and after surgery using standardized timed motor ta sks. We found that preoperative lentiform metabolism correlated signif icantly with improvement in contralateral motor scores at 1 week, 3 mo nths, and 6 months following unilateral pallidotomy (p < 0.03). Postop eratively, significant metabolic increases were noted in the primary m otor cortex, lateral premotor cortex, and dorsolateral prefrontal cort ex (p < 0.01) of the hemisphere that underwent surgery. Improvement in contralateral limb motor performance correlated significantly with su rgical declines in thalamic metabolism (p ( 0.01) and increases in lat eral frontal metabolism (p < 0.05). Principal components analysis disc losed a significant covariance pattern characterized by postoperative declines in ipsilateral lentiform and thalamic metabolism associated w ith bilateral increases in supplementary motor control metabolism. Sub ject scores for this pattern correlated significantly with improvement s in both contralateral and ipsilateral limb performance (p < 0.0005). These results suggest that pallidotomy reduced the preoperative overa ction of the inhibitory pallidothalamic projection. Clinical improveme nt may be associated with modulations in regional brain metabolism occ urring remote from the lesion site.