Efficacy and safety of stereotactic radiosurgery with gamma knife machine in patients with essential tremor: a systematic review and single-arm meta-analysis

Essential tremor (ET) is identified as the most prevalent movement disorder, primarily characterized by tremors in both upper extremities. The spectrum of surgical options for ET includes gamma knife radiosurgery (GKRS) and other stereotactic radiosurgery (SRS) modalities. Despite the limitations of these options, SRS is deemed an essential and indispensable approach. Our research aimed to assess the safety and efficacy of SRS, such as GKRS, on tremor control and the spectrum of associated adverse events in the treatment of ET, also focusing on long term outcomes of the procedure. We systematically conducted an extensive search across esteemed databases, which included PubMed, Cochrane Library, Embase, and Web of Science. We included studies involving individuals diagnosed with ET who had undergone GRKS treatment. A proportional rate was used to evaluate the outcomes in a 95% confidence interval. We included 12 studies comprising 414 patients. The treatment success rate with SRS was 86.6% (95% CI: 72.4-100%). Conversely, the overall failure rate was 13.4% (95% CI: 0.00 to 27.6%). Notably, post-procedure complications were observed in 9.7% of patients (95% CI: 5.8-13.6%). A meta-analysis of five studies revealed a statistically significant reduction of tremor from the FTM scale after treatment with GKRS (MD -2.1; 95% CI -2.5 to -1.6; p < 0.01; I² = 81%). A meta-analysis of eight studies revealed a statistically significant reduction in writing tremor from the FTM scale after treatment with GKRS (MD -1.7; 95% CI -2.3 to -1.2; p < 0.01; I² = 93%). A meta-analysis of six studies revealed a statistically significant reduction in drawing tremor from the FTM scale after treatment with GKRS (MD -1.9; 95% CI -2.5 to -1.4; p < 0.01; I² = 80%). Finally, a meta-analysis of three studies revealed a statistically significant reduction in drinking tremor from the FTM scale after treatment with GKRS (MD -1.6; 95% CI -1.9 to -1.3; p < 0.01; I² = 11%). Our findings show a high success rate and low failure of GKRS for ET. Thus, GKRS is a seemingly effective and safe option for managing these patients. The importance of this research lies in its contribution to the evolving landscape of radiosurgery, providing a robust basis for the clinical application of GKRS.