Intraoperative Motor Stimulation During Asleep Subthalamic Nucleus Deep Brain Stimulation Predicts Postoperative Motor Side Effects.

BACKGROUND AND

OBJECTIVES

Asleep subthalamic nucleus deep brain stimulation (STN-DBS) offers therapeutic benefits comparable with awake DBS for Parkinson disease (PD). However, it typically omits neurophysiological confirmation by microelectrode recordings and intraoperative stimulation, which may lead to postoperative motor side effects at low thresholds and necessitate lead repositioning. Therefore, identifying predictors of these side effects is essential. We hypothesized higher pulse widths stimulation intraoperatively will correlate with postoperative lower clinical pulse widths stimulation to identify motor side effects. Furthermore, we aimed to investigate the anatomic substrates underlying these side effects.

METHODS

We conducted a retrospective chart review to investigate whether higher pulse widths stimulation intraoperatively will correlate with postoperative lower clinical pulse widths stimulation to identify motor side effects in 19 patients. We intraoperatively stimulated patients with Parkinson disease undergoing asleep STN-DBS below 4 mA amplitude and pulse widths of 120 µs along the DBS electrode while visually assessing for muscle contractions, or lack thereof, in limb or cranial muscles. Similarly, mainly on postoperative day 1, we stimulated patients below 4 mA amplitude and pulse widths of 60 µs, which is clinically used. We used the Fisher exact test to analyze whether the occurrence of postoperative motor side effects was significantly associated with the occurrence of intraoperative motor activation. To assess the spatial relationship, we delineated corticobulbar tracts, corticospinal tracts, and frontal eye fields tract using tractography.

RESULTS

The threshold for intraoperative motor activation was significantly associated with the occurrence of postoperative motor side effects ( P value = .021). With tractography analysis, corticobulbar tracts and frontal eye fields were significantly closer to the STN-DBS contacts than corticospinal tracts ( P < .001).

CONCLUSION

In asleep STN-DBS, intraoperative motor activation at a pulse width of 120 µs below 4 mA is significantly associated with the occurrence of postoperative motor side effects below 4 mA.