Intra-operative Tongue Depression at High Pulse Width Stimulation During Asleep Deep Brain Stimulation May Predict Post-operative Dysarthria

Introduction: Asleep Deep Brain Stimulation (DBS) targeting the subthalamic nucleus (STN) for Parkinson’s disease (PD) has been made possible by recent advancements in imaging technology. Asleep DBS is increasingly being chosen by patients to reduce psychological burden. However, a key drawback is the inability to monitor intraoperative side effects, particularly postoperative dysarthria, which can affect patients' quality of life. Therefore, identifying predictors of dysarthria during asleep DBS is essential. Hence, we hypothesized that tongue depression during intraoperative test stimulation could predict postoperative dysarthria.

Methods: We studied nine PD patients who underwent asleep STN-DBS from February 2022 to January 2024. After DBS lead placement, test stimulation was applied at 120μs (higher than therapeutic pulse width) with 1-6mA intensity, and the threshold for tongue depression was recorded. Postoperatively, dysarthria occurrence was evaluated using 60μs stimulation with 1-6mA intensity. The chi-square test was used to evaluate the relationship between intraoperative tongue depression and postoperative dysarthria. Intraoperative tongue depression thresholds were categorized based on whether tongue depression occurred at 1-5 mA, and postoperative dysarthria thresholds were similarly grouped based on whether dysarthria occurred at 1-3 mA. The threshold for statistical significance was set at a p-value < 0.05.

Results: The mean age of the patients was 62 years (range: 50-70 years), consisting of one female and eight male participants. The chi-square test showed a significant association between the intraoperative tongue depression threshold at 120 μs stimulation and postoperative dysarthria (p = 0.024, Phi = 0.31).

Conclusion : Intraoperative high pulse width stimulation during asleep DBS may predict postoperative dysarthria.