UNILATERAL THALAMIC DEEP BRAIN-STIMULATION FOR REFRACTORY ESSENTIAL TREMOR AND PARKINSONS-DISEASE TREMOR

Objective: To determine the efficacy and tolerability of unilateral th alamic deep brain stimulation (DBS) for patients with medically refrac tory essential tremor (ET) and the tremor associated with Parkinson's disease (PD). Background: The tremor of ET and PD may produce function al disability despite optimal medical therapy. Several reports have de monstrated efficacy of thalamic DBS in this scenario. Methods: Preoper ative and S-month postoperative tremor ratings were compared in 33 pat ients (14 ET and 19 PD) with severe tremor. Evaluations included Unifi ed Parkinson's Disease Rating Scale (UPDRS) scores for PD patients and a modified Unified Tremor Rating Scale in ET patients. Open-label and blinded data (unknown activation status) were obtained. Results: ET p atients demonstrated an 83% reduction (p < 0.0001) in observed contral ateral arm tremor. All measures of tremor including writing samples, p ouring tests, subjective functional surveys, and disability scores imp roved significantly. PD patients demonstrated an 82% reduction (p < 0. 0001) in contralateral tremor and significant improvement in disabilit y and global impressions. There was, however, no meaningful improvemen t in other motor aspects of the disease, and the total UPDRS part II ( activities of daily living) score did not change. Adverse events, more common in ET patients, were generally mild and were usually eliminate d by adjustment of the device parameters. Conclusions: Thalamic DBS is a safe and effective treatment of ET and the tremor of PD. In PD, its use should be limited to patients in whom high-amplitude tremor resul ts directly in significant functional disability.