Chronic thalamic stimulation improves tremor and levodopa induced dyskinesias in Parkinson's disease.

Chronic thalamic stimulation was performed in 10 Parkinsonian patients with disabling tremor and poor response to drug therapy. During the stereotactic procedure, an electrode was introduced in the ventralis intermediate nucleus of the thalamus. Test stimulation was performed during the intra-operative procedure and a few days after surgery using an external stimulator. When tremor was obviously reduced by thalamic stimulation, an internal stimulator was implanted under the clavicle. Tremor was initially suppressed in all cases and reappeared whenever stimulation was stopped. Patients were followed for 22 to 34 months. Tremor was controlled in eight cases but reappeared after three months in two cases. Levodopa induced dyskinesias were observed before electrode implantation in 5 cases. They consisted of peak-dose choreic or ballistic dyskinesias in 4 cases and biphasic dystonic dyskinesias in 3 cases. Peak-dose dyskinesias were greatly improved or suppressed in all cases. Biphasic dyskinesias were improved in 2 cases. Thalamic stimulation was well tolerated. Mild dystonic hand posture related to the deep brain stimulation was observed in one case. No neuropsychological side-effects were noted. Thalamic stimulation could prove to be an adequate treatment for resistant tremor and levodopa induced dyskinesias.