Bilateral thalamic stimulation for the treatment of essential tremor

Objective: To determine the safety and efficacy of bilateral thalamic stimu lation in the treatment of essential tremor (ET). Methods: Nine ET patients with disabling tremor refractory to pharmacotherapy underwent bilateral st aged implants. Tremor was assessed by the Fahn-Tolosa-Marin Tremor Rating S cale at baseline 1 (before first implant), baseline 2 (before second implan t), and at 6-month and 1-year follow-up. Blinded evaluations were performed at 3 months. Associated changes in speech were evaluated in six patients. There were seven men and two women with a mean age of 73.8 years. Results: There was a significant improvement in the mean total tremor score from a b aseline of 66.1 +/- 11.6 to 28.4 +/- 12.8 12 months after the second surger y. Similarly, the mean motor tremor subscore was 20.1 +/- 5.0 before the fi rst surgery and improved significantly to 14.1 +/- 3.6 before the second su rgery. Motor tremor scores 6 months after the second surgery (6.0 +/- 3.7) and 12 months after the second surgery (7.5 +/- 3.9) also improved signific antly relative to the preoperative scores. The mean activities of daily liv ing (ADL) subscore at baseline was 18.2 +/- 2.9 and improved significantly before the second surgery to 9.0 +/- 3.2. These ADL scores further improved 6 months (6.2 +/- 5.2) and 12 months (7.9 +/- 5.7) following the second su rgery, but these gains were not significant. Blinded evaluations also revea led a similar degree of improvement. Complications were noted in five patie nts: asymptomatic intracranial hematoma (1), postoperative seizures (1), a hematoma over the implanted pulse generator (IPG) (1), lead repositioning ( 1), and IPG malfunction (1). Adverse effects related to stimulation were mi ld and resolved with adjustment of the stimulation parameters. Three of the six patients demonstrated worsening of dysarthria with both stimulators on . Conclusions: Bilateral thalamic stimulation is effective in reducing trem or and functional disability in ET; however, dysarthria is a possible compl ication.