Depression Scores following Ventral Intermediate Nucleus Deep Brain Stimulation for Essential Tremor: A Meta-Analysis

Background: Essential tremor (ET) patients present with both motor and non-motor symptoms including depression. Although deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) is used to treat motor symptoms of ET, there is no consensus as to how VIM DBS influences non-motor symptoms, specifically depression.

Objective: The objective of this study was to conduct a meta-analysis of available studies investigating change in pre- to postoperative depression scores as measured by Beck Depression Inventory (BDI) in ET patients receiving VIM DBS.

Methods: Inclusion criteria were randomized control trials or observational studies of patients undergoing unilateral/bilateral VIM DBS. Non-ET patients, case reports, patients <18 years old, only non-VIM electrode placement, non-English articles, and abstracts were excluded. The primary outcome was change in BDI score from the preoperative time point to the last available follow-up. Pooled estimates of overall effect for BDI standardized mean difference were calculated using random effects models with the inverse variance method.

Results: Seven studies divided into eight cohorts for a total of 281 ET patients met inclusion criteria. Pooled preoperative BDI score was 12.44 (95% CI [6.63-18.25]). A statistically significant decrease in depression scores was observed postoperatively (SMD = -0.29, 95% CI [-0.46 to -0.13], p = 0.0006). Pooled postoperative BDI score was 9.18 (95% CI [4.98-13.38]). A supplementary analysis which included an additional study with an estimated standard deviation at last follow-up was conducted. There was also a statistically significant decrease in depression postoperatively (9 cohorts, n = 352, SMD = -0.31, 95% CI [-0.46 to -0.16], p < 0.0001).

Conclusions: Both quantitative and qualitative analyses of the existing literature suggest that VIM DBS improves depression postoperatively among ET patients. These results may guide surgical risk-benefit analysis and counseling for ET patients undergoing VIM DBS.