Stereotactic radiotherapy on Parkinson's disease induced tremors - a systematic review

Background: Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive disability due to bradykinesia, rigidity, and rest tremors. Especially in the treatment of tremors, pharmacological options often fall short. Invasive treatments such as deep brain stimulation are unsuitable in selected patients. Stereotactic radiotherapy (SRT) is a non-invasive alternative. However, implementation is hindered by inconsistent findings across studies. Materials and Methods: This study aims to evaluate the effect of SRT on tremors in PD patients. A PRISMA-guided systematic review identified 183 records. Six studies (n = 193 patients) met inclusion criteria. Outcomes were assessed after 12 months of SRT treatment. Results: All included studies used single-fraction SRT, prescribed doses ranged from 85-165 Gy, with 130-140 Gy being most frequently used. The ventral intermediate nucleus (VIM) was the most commonly targeted structure in three of the six studies. Across all studies tremor improvement was reported in 71 %-100 % of cases, with severity reduction of 38 %-67 % and tremor elimination in three studies varying from 0 % to 70 % of patients. Three studies noted medication reductions in 6 %-75 % of cases. Quality of life (QoL) and tremor recurrence were inconsistently reported: only one study reported no significant QoL improvement. Recurrence rates ranged from 3 %-24 %. Adverse events were present in 7 (7 %) patients. Conclusion: SRT is a promising non-invasive treatment for medically refractory PD tremor, with substantial tremor reduction and low toxicity. However, limitations such as the inconsistent reporting affect the strength of the findings. Future research should emphasize standardized reporting of treatment parameters and outcomes to strengthen evidence on SRT efficacy.