Importance of the initial response to GPi deep brain stimulation in dystonia: A nine year quality of life study

Background: Long-term efficacy of deep brain stimulation (DBS) on health-related quality-of-life (HRQoL) for isolated dystonia is not well established. This study aims to determine the long-term impact of DBS on HRQoL outcomes and identify clinical predictors. Methods: We retrospectively investigated 16 inherited or idiopathic isolated dystonia patients treated with bilateral globus pallidus internus DBS who were followed beyond 9 years at our center. The cohort consisted of 9 males, 7 females; 10 generalized, 6 segmental; mean (range) age at implantation, 37.0 (8-67) years; mean follow-up duration after implantation, 10.9 (9-13) years. We employed the Unified Dystonia Rating Scale for motor and Short Form Health Survey for HRQoL assessments to monitor the change longitudinally. We analyzed the changes in motor and HRQoL at 1-2 years (short-term) and >= 9 years (long-term) follow-up as compared to baseline with a Wilcoxon signed-rank test. We assessed the factors that predicted motor and HRQoL improvement with univariate regression analyses. Results: Motor (41.6%; p = 0.004) and HRQoL (total score, p = 0.039) improvements remained significant at long-term follow-up and, in the regression analysis, change in HRQoL outcomes correlated significantly with change in motor outcomes (R-2 = 0.384, p = 0.010). Additionally, short-term motor and HRQoL improvements predicted the long-term motor (R-2 = 0.384, p = 0.010) and HRQoL (total score, R-2 = 0.594, p < 0.001) outcomes, respectively. Conclusion: Motor and HRQoL improvements with DBS in isolated dystonia remain sustained for nearly a decade and may largely be predictable by the short-term response to DBS.