Deep brain stimulation for arm tremor: one-year blinded follow-up of a randomized trial

OBJECTIVE: To present the secondary endpoints at one-year blinded follow-up from our randomized controlled study, that compared the efficacy of DBS in the ventral-intermediate thalamic nucleus (VIM) with the posterior subthalamic area (PSA) three months each in crossover design, and showed significantly greater reduction of the Sum dominant arm tremor score (Fahn-Tolosa-Marin) during the PSA-DBS period. The outcomes at one year are now reported to verify target choice and sustained benefit with clinically optimized free programming. METHODS: Forty-five patients with isolated or combined arm action tremor received four-level DBS leads to reach both VIM (upper two levels) and PSA (lower two), and were randomized post-operatively to VIM-DBS month 1-3 followed by PSA-DBS month 4-6, or vice versa. Thereafter electrode choice was free as judged by best clinical outcome. Predefined secondary endpoints were the tremor score improvements from preoperative to the one-year follow-up for dominant and non-dominant arm, other body regions, total score, two patient-rated measures and adverse events. RESULTS: At the one-year follow-up, Sum dominant arm tremor scores had improved from median 24 at baseline to 4 (p<.001, n = 43), corresponding to median 79% improvement. All other secondary endpoints also improved significantly (p<.001). Median action tremor improvement was for Essential tremor(ET) 83%, for Parkinson´s disease(PD) and Dystonic tremor 100% and for Cerebellar tremor 55%. Over 90% of stimulated contacts were in PSA. INTERPRETATION: At one year, good and sustained tremor suppression from PSA-DBS was confirmed in ET, PD and Dystonic tremor. Suppression of Cerebellar tremor was more variable. TRIAL REGISTRATION: NCT03156517, May 29, 2017.