CHRONIC ELECTRICAL-STIMULATION OF THE VENTRALIS INTERMEDIUS NUCLEUS OF THE THALAMUS AS A TREATMENT OF MOVEMENT-DISORDERS

Tremor was suppressed by test stimulation of the thalamic ventralis in termedius (VIM) nucleus at high frequency (130 Hz) during stereotaxy i n nonanesthetized patients suffering from Parkinson's disease or essen tial tremor. Ventralis intermedius stimulation has since been used by the authors over the last 8 years as a treatment in 117 patients with movement disorders (80 cases of Parkinson's disease, 20 cases of essen tial tremor, and 17 cases of various dyskinesias and dystonias includi ng four multiple sclerosis). Chronic electrodes were stereotactically implanted in the VIM and connected to a programmable stimulator. Resul ts depend on the indication. In Parkinson's disease patients, tremor, but not bradykinesia and rigidity, was selectively suppressed for as l ong as 8 years. Administration of L-Dopa was decreased by more than 30 % in 40 Parkinson's disease patients. In essential tremor patients, re sults were satisfactory but deteriorated with time in 18.5% of cases, mainly for patients who presented an action component of their tremor. In other types of dyskinesias (except multiple sclerosis), results we re much less favorable. Fifty-nine patients underwent bilateral implan tation and 14 other patients received implantation contralateral to a previous thalamotomy. Thirty-seven patients (31.6%) experienced minor side effects, which were always well tolerated and immediately reversi ble. Three secondary scalp infections led to temporary removal of the implanted material. There was no permanent morbidity. This tremor supp ression effect could be due to the inhibition or jamming of a retroact ive loop. Chronic VIM stimulation, which is reversible, adaptable, and well tolerated even by patients undergoing bilateral surgery (74 of 1 17 patients) and by elderly patients, should replace thalamotomy in th e regular surgical treatment of parkinsonian and essential tremors.