TREATMENT OF TREMOR IN PARKINSONS-DISEASE BY SUBTHALAMIC NUCLEUS STIMULATION

The recent resurgent interest in functional surgery for the treatment of Parkinson's disease (PD) has focused on the effects on akinesia and levodopa-induced dyskinesia. Stimulation of the subthalamic nucleus ( STN) improves akinesia and rigidity but its effects on tremor have not been studied. The objective of this study was to assess the efficacy of STN stimulation on tremor in patients with the complete parkinsonia n triad with motor fluctuations. Of 27 consecutive patients with STN s timulation (26 bilateral), 15 exhibited tremor rated at least 2/4 acco rding to item 20 (rest tremor) of the Unified Parkinson's Disease Rati ng Scale (UPDRS) in at least one limb. The mean preoperative tremor sc ore was 11.3 +/- 5.6 in off-drug and 1.2 +/- 2.4 in on-drug conditions . The postoperative tremor scores at the last follow up (from 1-12 mon ths) were 2.2 +/- 2.2 off-drug/on-stimulation and 0.2 +/- 0.4 on-drug/ on-stimulation. Both rest and action tremors were improved in all pati ents. The UPDRS tremor score was reduced by 80%, rigidity score by 65% , and akinesia score by 51% on average. For the three symptoms, the st imulation effect was close to that induced before surgery by a suprath reshold dose of levodopa given in the morning. STN stimulation can be considered an interesting alternative to thalamic or internal pallidal surgery even in PD patients with severe high-amplitude tremor. In kee ping with electrophysiological data in monkeys rendered parkinsonian b y MPTP injections, our results emphasize the importance of the oscilla tion of a neuronal loop involving the STN in the pathophysiology of pa rkinsonian tremor.