Objective: To characterize the clinical improvement associated with MLE and its temporal progression. In addition, to analyze postoperative images and investigate whether there is a correlation between MLE and the anatomical position of the electrodes.

Background: Subthalamic deep brain stimulation (STN-DBS) is an effective long-term treatment for Parkinson’s disease (PD)¹. A transient improvement in symptoms, known as the microlesional effect (MLE), has been observed after electrode implantation and before stimulation begins^2,3. The MLE has been proposed as a possible prognostic factor for functional outcomes, although this remains unclear. It is currently known that the MLE is more noticeable during the first week after DBS surgery and has been associated with better motor outcomes in the med-term follow-up^4,5. We hypothesize that the magnitude of the MLE in PD patients undergoing STN-DBS may be associated with the anatomical positioning of the electrodes.

Method: Thirty patients with PD who underwent bilateral STN-DBS were evaluated. Motor symptoms and quality-of-life were assessed using validated scales pre- and post-operatively (24h, 48-72 hrs, 7 and 30 days). Electrode positioning was analyzed using advanced image reconstruction, and correlations between the magnitude of MLE and electrode placement were examined.

Results: MLE was observed in 27 of 30 patients (90%), peak effect at 48-72 hours after surgery. A significant association was observed between the magnitude of MLE and long-term clinical outcomes (MDS-UPDRS III at one month). In addition, a significant relationship was observed between the optimal location of both electrodes and the MLE (p:0.049).

Conclusion: A quantifiable MLE is observed in patients undergoing STN-DBS, reaching its maximum effect at 48-72 hours post-surgery. In this study, the MLE was associated with improved clinical outcomes at follow-up. Additionally, a higher MLE correlated with optimal electrode placement, with no differences observed in the intensity of stimulation parameters

References: 1. Moro e, Lozano aM, pollak p, et al. Long-term results of a multicenter study on subthalamic and pallidal stimulation in parkinson’s disease. Mov Disord 2010;25:578–86.
2. Soler-Rico M, Peeters JB, Joris V, Delavallée M, Duprez T, Raftopoulos C. MRI-guided DBS of STN under general anesthesia for Parkinson’s disease: results and microlesion effect analysis. Acta Neurochir (Wien). 2022 Sep 1;164(9):2279–86.
3. Aygun D, Dere UA, Yildiz O, Temel Y, Kocabicak E. Characterizing the intraoperative microelectrode recording-induced microlesion effect on motor symptoms in patients with parkinson’s disease undergoing deep brain stimulation of the subthalamic nucleus. Turk Neurosurg. 2019;29(3):430–3.
4. Tykocki T, Nauman P, Koziara H, Mandat T. Microlesion Effect as a Predictor of the Effectiveness of Subthalamic Deep Brain Stimulation for Parkinson’s Disease. Stereotact Funct Neurosurg. 2013 Jan;91(1):12–7.
5. Mann JM, Foote KD, Garvan CW, Fernandez HH, Jacobson IV CE, Rodriguez RL, et al. Brain penetration effects of microelectrodes and DBS leads in STN or GPi. J Neurol Neurosurg Psychiatry. 2009 Jul;80(7):794–7.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/correlation-between-the-microlesional-effect-of-subthalamic-deep-brain-stimulation-and-postoperative-imaging-in-parkinsons-disease/