Outcomes and Adverse Effects of Deep Brain Stimulation on the Ventral Intermediate Nucleus in Patients with Essential Tremor

Abstract

Objective. This study was aimed at identifying the potential outcome predictors, comparing the efficacy in patients with different tremor characteristics, and summarizing the adverse effect rates (AERs) of deep brain stimulation on the ventral intermediate nucleus (VIM-DBS) for essential tremor (ET). Methods. An extensive search of articles published to date in 2019 was conducted, and two main aspects were analyzed. Improvement was calculated as a percentage of change in any objective tremor rating scale (TRS) and analyzed by subgroup analyses of patients’ tremor characteristics, laterality, and stimulation parameters. Furthermore, the AERs were analyzed as follows: the adverse effects (AEs) were classified as stimulation-related, surgical-related, or device-related effects. A simple regression analysis was used to identify the potential prognostic factors, and a two-sample mean-comparison test was used to verify the statistical significance of the subgroup analyses. Results. Forty-six articles involving 1714 patients were included in the meta-analysis. The pooled improvement in any objective TRS score was 61.3% (95% CI: 0.564-0.660) at the mean follow-up visit (20.0±17.3 months). The midline and extremity symptoms showed consistent improvement (P=0.440), and the results of the comparison of postural and kinetic tremor were the same (P=0.219). In addition, the improvement in rest tremor was similar to that in action tremor (OR=2.759, P=0.120). In the simple regression analysis, the preoperative Fahn-Tolosa-Marin Tremor Rating Scale (FTM-TRS) scores and follow-up time were negatively correlated with the percentage change in any objective TRS score (P<0.05). The most common adverse event was dysarthria (10.5%), which is a stimulation-related AE (23.6%), while the rates of the surgical-related and device-related AEs were 6.4% and 11.5%, respectively. Conclusion. VIM-DBS is an efficient and safe surgical method in ET, and the efficacy was not affected by the body distribution of tremor, age at surgery, and disease duration. Lower preoperative FTM-TRS scores likely indicate greater improvement, and the effect of VIM-DBS declines over time.

Stimulation-Induced Side Effects of Deep Brain Stimulation in the Ventralis Intermedius and Posterior Subthalamic Area for Essential Tremor

“…The strengths of our study are the large number of patients (115 implanted DBS electrodes in 93 patients with ET) and evaluation of long-term outcomes. In the present study, dysarthria, gait disturbance, and paresthesia were the most common stimulation-induced side effects, consistent with previous reports ( 21 – 23 ). We identified that single electrode DBS targeting both the PSA and VIM can be used when stimulation-induced side effects occur.…”

Habituation After Deep Brain Stimulation in Tremor Syndromes: Prevalence, Risk Factors and Long-Term Outcomes

“…The pooled treatment effect was 60.3% improvement in objective Tremor Rating Scale (TRS) scores at 20 months (+/– 17.3). Correlation with outcome was seen only with pre-operative TRS scores and follow-up time; both negatively correlated with the clinical outcome ( 36 ). It had previously been reported that pre-operative cerebellar dysfunction was a risk factor for the development of early “tolerance” ( 37 ).…”

“…The DBS target for tremor suppression is of particular interest in view of the progressive loss of tremor benefit seen with VIM DBS in ET ( 36 ). Given the important role the cerebellothalamic tract plays in tremor, the PSA/cZI has been used as an alternative DBS target.…”

Neuromodulation Approaches in Parkinson’s Disease Using Deep Brain Stimulation and Transcranial Magnetic Stimulation

“…Another target that has been used for tremor predominate disease is the ventral intermediate nucleus (VIM) of the thalamus. There has been extensive experience with this target in the treatment of essential tremor (ET) with high rates of efficacy, 30 but use of this target with PD is less common as it does not have the associated benefits of reduction of bradykinesia and rigidity seen with either STN or GPi stimulation. The surgical approach to all 3 targets is similar, such that target selection should be based on the symptom characteristics of the patient; however, of the 3, the STN is the smallest target, such that lack of efficacy due to poorly positioned electrodes is seen more frequently with this target.…”