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Abstract
Objective: Compare the effects of ventral intermediate nucleus (VIM) deep brain stimulation (DBS) in dystonic tremor (DT) versus essential tremor (ET).
Background: DT is frequently misdiagnosed as ET and treatment approaches frequently overlap despite a distinct pathophysiology underlying these disorders. VIM DBS is a proven treatment for select cases of ET however there is scant literature on the effectiveness of DBS in DT. Only few case series have detailed outcomes of VIM DBS in DT and a systematic comparison of outcomes in DT versus ET is clearly lacking.
Design/Methods: 23 DT patients and 43 ET patients who underwent unilateral or bilateral VIM DBS were retrospectively analyzed. Tremor outcome was longitudinally monitored with the Fahn-Tolosa-Marin tremor rating scale at six months, 1 year, 2–3 years, 4–5 years, and last follow-up when compared to baseline preoperative scores. DBS outcome for each group was analyzed with the Wilcoxon signed-rank test and between-group comparison of change in scores in DT versus ET was performed with Mann–Whitney U test.
Results: Compared to baseline, the total, activities of daily living (ADL), and motor scores in DT significantly improved at six months and 1 year only (p < 0.001), however the contralateral composite arm tremor score (rest, postural, and kinetic) remained significantly improved up to 5 years after surgery. Improvement in arm tremor was not significantly different between DT and ET patients at each follow-up visit (p > 0.05). While there was no difference in the total and the motor scores between DT and ET throughout the follow-up, ADL improvements were significantly less in the DT group.
Conclusions: VIM DBS effectively controls arm tremor in DT. DBS benefits in DT are similar to ET but differ in patient-reported ADL scores, possibly due to insufficient control of concomitant dystonia symptoms. Clinical improvement only slightly favoring ET matches our bedside observations.