Bilateral thalamic deep brain stimulation: midline tremor control

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Abstract
Objectives: To determine the efficacy of bilateral deep brain stimulation (DBS) for management of midline tremor (head, voice, tongue, trunk) in patients with essential tremor. Design: Prospective assessment of tremor at baseline (presurgical), and postoperatively at 1, 3, and 12 months, and annually thereafter. Methods: A clinical series of 22 individuals undergoing staged, bilateral DBS for treatment of essential tremor. The tremor rating scale was the primary outcome measure. Results: Midline tremor showed significant improvement with stimulation “on” at nearly every postoperative interval when compared with stimulation “off” and with baseline tremor. Bilateral stimulation was associated with a significant incremental improvement in midline tremor control compared with unilateral stimulation: average “stimulation on” percentage change in midline tremor from the unilateral to bilateral period was 81%. Head and voice tremor showed the most consistent improvement. Among those requiring a change in stimulation parameters because of side effects, dysarthria, disequilibrium, motor disturbances, and paraesthesiae were the most common. Dysarthria was more common with bilateral (n = 6; 27%) than with unilateral (n = 0) stimulation. Stimulation parameters remained largely unchanged after the first three months. Nine of 44 leads placed (20%) required subsequent repositioning or replacement. Conclusions: Unilateral thalamic stimulation significantly improves midline tremor, and subsequent bilateral thalamic stimulation offers an additional incremental improvement in midline tremor control.