Objective: To evaluate the consistency and effect size as well as the incidence of persistent side effects of lesional neurosurgical interventions using radiofrequency ablation (RF), focused ultrasound (MRIgFUS) and gamma knife (GK) in the treatment of tremor due to Parkinson`s disease (PD), Essential Tremor (ET) and Multiple Sclerosis (MS). 

Background: The introduction of incision-less lesional functional neurosurgery by GK and MRIgFUS has again created interest in lesional treatments for tremor disorders. 

Methods: Systematic review of Medline and Cochrane databases of lesional neurosurgical interventions for tremor published between January 1990 and June 2016 following PRISMA guidelines. Studies with a minimum of n=5, follow-up ≥ 3 months and tremor quantification using a validated scale were selected for random effects meta-analysis based on standardized mean difference/Hedge`s g. All studies reporting persistent side effects after unilateral interventions were included in the safety assessment.

Results: Out of 1247 abstracts screened, 84 published peer-reviewed studies homogeneous for tremor etiology, surgical target and intervention were included. Based on data from 1198 patients, effect on PD tremor was better when targeted at the ventral intermediate nucleus (V.im.) by RF (Hedge`s g: -4.15; 95% CI: -5.13 /-3.17) over V.im. by GK (-2.2; -3.62/-0.78), subthalamic nucleus (STN) by RF (-1.12; -1.4/-0.84) and globus pallidus internus (GPi) by RF (-0.88; -1.19/-0.57). For ET V.im. ablation by MRIgFUS (-2.47; -2.83/-2.12) showed similar tremor reduction to V.im. ablation by RF (-2.46; -2.56/-2.35) and a stronger effect than V.im. ablation by GK (-2.13; -3.78/-0.48). For MS tremor V.im. ablation by GK (-1.96; -3.12/-0.81) had a greater effect size than by RF (-1.63; -2.56/-0.7). 

Rates of persistent side effects after unilateral lesions in PD were 15.9±14.7% (RF V.im.), 14.7±5.0% (RF STN), 8.3±15.1% (RF GPi), 1.6±0.8% (GK V.im.) and 4.9±6.9% (MRIgFUS V.im.). For ET rates were 6.3±7.1% (RF V.im.), 1.9±2.4% (GK V.im.) and 10.9±11.4% (MRIgFUS V.im.) and for MS 37.7±23.9% (RF V.im.).

Conclusions: This comprehensive comparison of safety and efficacy of lesional neurosurgical interventions for tremor disorders defines the benchmark for and guides future developments of incision-less techniques. Lesion target and technique have different effects according to tremor etiology.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/functional-lesional-neurosurgery-for-tremor-a-systematic-review-and-meta-analysis/