Control of tremor and involuntary movement disorders by chronic stereotactic stimulation of the ventral intermediate thalamic nucleus.

The authors report on the long-term results of chronic stereotactic stimulation of the ventralis intermedius thalamic nucleus performed in 14 cases of disabling and intractable tremor. There were 10 patients with parkinsonian tremor and four with essential tremor. Three of the 10 parkinsonian patients had previously undergone contralateral thalamotomy. Tremor was assessed by clinical evaluation, surface electromyography, accelerometer, and videotape recordings before and after stimulation. The deep-brain electrode was implanted in the ventralis intermedius nucleus according to stereotactic procedure and connected to a subcutaneous pulse generator after a stimulation test period. Tremor suppression or reduction was obtained in all cases with high-frequency (130 Hz) stimulation. Marked functional improvement was maintained in 11 patients with a mean follow-up interval of 17 months. Levodopa-induced dyskinesias observed in five parkinsonian patients prior to surgery were improved or suppressed in four cases by thalamic stimulation. Stimulation was continued during the day and stopped at night in eight cases. Six patients were stimulated night and day to avoid a rebound effect which appeared as soon as the pulse generator was stopped. The only side effects were hand tonic posture in one case and persistent paresthesia in another case. The mechanism of action of this attractive treatment may be a functional alteration of the thalamic discharging area. The authors conclude that this technique is a good alternative to thalamotomy, especially when the risks of high-frequency coagulation are severe in frail and older patients.