Stereotatic radiosurgery for the treatment of motor symptoms in Parkinson's disease: A systematic review

Background: Stereotaxic Radiosurgery (SRS) is a non-invasive lesioning technique for movement disorders when patients cannot undergo DBS due to medical comorbidities. Objective: To describe and summarize the literature on SRS's application and physical parameters for Parkinson's disease (PD) motor symptoms. Methods: The MEDLINE/PUBMED and EMBASE databases were searched in July 2022 following the PRISMA guideline. Two independent reviewers screened data from 425 articles. The level of evidence followed the Oxford Centre for Evidence-Based Medicine. Pertinent details for each study regarding participants, physical parameters, and results were extracted. Results: Twelve studies reported that 454 PD patients underwent Gamma Knife (R) (GK). The mean improvement time of the treated symptoms was three months after GK. Tremor is the most common symptom investigated, with success rates ranging from 47.5% to 93.9%. Few studies were conducted for caudatotomy (GKC) and pallidotomy (GKP), which presented an improvement for dyskinesia and bradykinesia. Physical parameters were similar with doses ranging from 110 to 200 Gy, use of a 4-mm collimator with an advanced imaging locator system, and coordinates were obtained from available stereotactic atlases. Conclusions: GK thalamotomy is a good alternative for treating tremor; however, its effects are delayed, and there are cases in which it can regress after years. The outcomes of GKC and GKP seem to be promising. The existing studies are more limited, and effects need to be better investigated.