Microlesion effect as a predictor of the effectiveness of subthalamic deep brain stimulation for Parkinson's disease.

Background: Microlesion effect (MLE) is a commonly observed phenomenon after electrode insertion into the subthalamic nucleus (STN) for deep brain stimulation (DBS).
Objectives: The aim of this study was to determine the presence of the MLE in the early postoperative period and the relationship between MLE and STN DBS.
Methods: 74 patients with Parkinson's disease were included in this study. Motor symptoms were evaluated preoperatively, within 48 h after electrode implantation and at 6 months with United Parkinson's Disease Rating Scale part III (UPDRS-III). According to the improvement level with MLE, all participants were stratified into three groups: (1) less than 20%; (2) 20-40%, and (3) more than 40% in OFF medication states. The degree of improvement in UPDRS-III with DBS ON for each MLE group was assessed at the 6-month follow-up. Regression analysis was applied for the evaluation of the relationship between MLE and improvement with DBS ON.
Results: Mean results in UPDRS-III with the MLE in ON and OFF medication states were 22.1 ± 10.5 and 42.1 ± 14 points, respectively. At the 6-month follow-up, with active stimulation, results tended to further ameliorate to 14.6 (59.4%) points in ON and 20.8 (55.3%) in OFF. Mean improvement in MLE groups were: 33.6% group 1, 47.5% group 2 and 61.4% group 3. Regression analysis revealed a positive correlation between the MLE and results at 6 months with DBS ON.
Conclusion: Results proved the presence of MLE in the early postoperative period. Furthermore, a positive correlation between MLE and improvement degree with active stimulation was observed.
(Copyright © 2012 S. Karger AG, Basel.)