Enhanced Frameless Stereotactic Guidance Using Triggered EMG for Foramen Ovale Targeting in TN RFTA

Overview

This study introduces a novel technique combining triggered electromyography (T-EMG) with frameless stereotactic guidance to improve the accuracy of foramen ovale cannulation during radio-frequency thermal ablation (RFTA) for trigeminal neuralgia (TN) under general anesthesia. In 27 procedures, the foramen ovale was successfully identified in 96% of cases, with 61.5% of patients experiencing pain improvement and no mastication deficits reported postoperatively.

Background

Trigeminal neuralgia is a severe neuropathic facial pain condition affecting up to 14 per 100,000 individuals annually worldwide. Radio-frequency thermal ablation (RFTA) is a minimally invasive surgical option favored for patients with prior microvascular decompression, multiple sclerosis, or trigeminal nerve damage. Traditional RFTA requires patient feedback during awake surgery for precise electrode placement, but this can be limited by discomfort and unreliable responses. Advances in stereotactic navigation and neurophysiology have improved targeting, yet challenges remain in accurately cannulating the foramen ovale, especially in elderly patients with anatomical variations or calcifications.

Data Highlights

Key Findings

• Triggered electromyography (T-EMG) combined with frameless stereotactic navigation enables real-time dynamic mapping of the V3 motor branch to accurately identify the foramen ovale under general anesthesia.
• Successful cannulation of the foramen ovale was achieved in 96% of procedures, with only one aborted case due to calcification.
• The median stimulus intensity required to elicit a compound muscle action potential (CMAP) from the masseter muscle was 4.5 mA, allowing precise localization.
• Postoperative mastication function was preserved in all patients, indicating procedural safety.
• At an average follow-up of 4.7 months, 61.5% of patients reported improvement in facial pain, supporting clinical efficacy.
• The technique facilitates targeting of specific trigeminal nerve branches (V1, V2, V3) with continuous stimulation to confirm needle position.

Clinical Implications

This T-EMG guided frameless stereotactic approach allows surgeons to perform RFTA for trigeminal neuralgia with improved accuracy and safety under general anesthesia, eliminating the need for patient feedback during awake procedures. It reduces the risk of complications related to inaccurate foramen ovale cannulation and preserves mastication function. Clinicians may consider adopting this technique to enhance procedural success and patient outcomes, especially in patients with challenging anatomy or intolerance to awake surgery.

Conclusion

The integration of triggered electromyography with frameless stereotactic guidance significantly enhances the precision of foramen ovale targeting during RFTA for trigeminal neuralgia, resulting in high procedural success and favorable pain outcomes without compromising motor function.

References

1. International Classification of Headache Disorders (ICHD-3) -- Diagnostic Criteria for Trigeminal Neuralgia
2. Cadwell Laboratory -- Cadwell Cascade Pro Neuromonitoring System
3. Boston Scientific -- Tew Trigeminal Needle Stylet