Epidural Electrode Placement for Motor Cortex Stimulation Under GA in Refractory Trigeminal Pain

Overview

This report details a novel surgical technique for motor cortex stimulation (MCS) under general anesthesia using intraoperative electrophysiological monitoring to treat refractory trigeminal neuropathic pain. The method enables precise epidural electrode placement confirmed by motor evoked potentials (MEPs), improving patient comfort by avoiding awake procedures.

Background

Trigeminal neuralgia (TGN) causes severe facial pain, with 44% of patients experiencing refractory symptoms despite pharmacotherapy. Surgical options like microvascular decompression and radiosurgery exist but may fail in refractory cases. Motor cortex stimulation (MCS) has shown median pain reductions of 70% but traditionally requires awake surgery for electrode positioning confirmation. The described technique uses intraoperative electrophysiological monitoring under general anesthesia to localize the central sulcus and confirm electrode placement, offering a less distressing alternative.

Data Highlights

Intraoperative monitoring involved recording motor evoked potentials (MEPs) from facial muscles (orbicularis oris and frontalis) after monopolar epidural stimulation at 7 mA. Postoperative CT with 3D reconstruction confirmed accurate electrode positioning over the motor cortex. The surgical approach included a 2.5 cm skin incision and a 1 cm burr hole placed 2 cm paramedian, with electrode insertion guided by neuronavigation and phase reversal of somatosensory evoked potentials (SEP) to identify the central sulcus.

Key Findings

• Motor cortex stimulation (MCS) can be effectively performed under general anesthesia using intraoperative electrophysiological monitoring.
• Intraoperative motor evoked potentials (MEPs) elicited via epidural electrodes confirm correct electrode placement without requiring patient wakefulness.
• Neuronavigation combined with somatosensory evoked potential (SEP) phase reversal reliably localizes the central sulcus for electrode positioning.
• The described technique reduces patient discomfort associated with awake craniotomy procedures.
• Postoperative imaging confirms accurate electrode placement, supporting the reliability of intraoperative electrophysiological guidance.

Clinical Implications

This technique offers a viable alternative to awake surgery for MCS electrode placement in refractory trigeminal neuropathic pain, improving patient comfort and procedural tolerability. Incorporating intraoperative electrophysiological monitoring and neuronavigation ensures precise electrode localization, potentially enhancing treatment efficacy. Clinicians may consider this approach to expand neuromodulation options for patients unsuitable for awake procedures.

Conclusion

Intraoperative electrophysiological monitoring under general anesthesia enables accurate epidural electrode placement for motor cortex stimulation in refractory trigeminal neuropathic pain, providing a patient-friendly alternative to awake surgery. This method may improve treatment accessibility and outcomes in this challenging patient population.

References

1. Author/Source/Year -- Various references cited in article