LONG-TERM ELECTRICAL INHIBITION OF DEEP BRAIN TARGETS IN MOVEMENT-DISORDERS

Stimulation of the thalamic nucleus ventralis intermedius (Vim) at hig h (130-Hz) frequency has been used over the last 8 years as a treatmen t in 134 patients with movement disorders (91 Parkinson's disease [PD] , 23 essential tremor [ET], 21 various dyskinesias and dystonias, incl uding four multiple sclerosis [MS]), implanted with long-term electrod es connected to a programable stimulator. In PD patients, tremor was s electively suppressed for less than or equal to 11 years. In ET patien ts, results were satisfactory, but in 35% of the cases deteriorated wi th time, when tremor had an action component. Other types of dyskinesi as were much less influenced. Sixty-eight patients were bilaterally im planted, and 14 were implanted contralateral to a previous thalamotomy . Side effects were often minor, well tolerated, and immediately rever sible. Three secondary scalp infections led to temporary removal of im planted material. There was no permanent morbidity. Long-term Vim stim ulation, which is reversible, adaptable, and well tolerated, even by b ilaterally operated-on (68 of 134) and by elderly patients, should rep lace thalamotomy in the regular surgical treatment of parkinsonian and essential tremors. More recently, we stimulated the subthalamic nucle us (STN) in 51 patients (44 bilateral) and the globus pallidus internu s (GPi) in 12 patients (seven bilateral). STN stimulation has a specta cular effect on akinesia and rigidity and may improve the patients so as to maintain them all day at a level similar Co their best ''on'' pe riods. A 30-50% reduction in drug dosage was possible in most of the p atients. GPi stimulation has indications and effects similar to those of pallidectomy: abnormal involuntary movements are totally suppressed , whereas effects on akinesia and rigidity are not so important as the y are with STN stimulation. For all three targets, morbidity is low an d reversible, even when bilateral implantations are performed. The dee p-brain stimulation method has now proved its safety as compared with ablative surgery and is able to provide a significant improvement to t hese severely disabled patients. Long-term follow up is establishing t he security of the method, which should be considered in earlier stage s of the disease actively to participate to rehabilitation.