1077 A Novel Trigeminotrigeminal/Trigeminofacial Reflex is Present in Trigeminal Neuralgia and can be used to Direct Radiofrequency Rhizotomy

INTRODUCTION: Trigeminal neuralgia is amongst the most painful conditions in humans. During procedures targeting the trigeminal nerve in trigeminal neuralgia, we noted a novel electrophysiologic reflex present only in patients with trigeminal neuralgia. We devised a method for performance of radiofrequency rhizotomy under general anesthetic with neurophysiology monitoring using this reflex. METHODS: This was a prospective, observational study of all patients undergoing surgery involving exposure of the trigeminal nerve. Demographic information was collected. During stimulation of the trigeminal nerve for identification, we tested for the presence of the reflex. The reflex was noted in all patients with trigeminal neuralgia but not in those without. RESULTS: A total of 51 patients were studied. 12 patients undergoing microvascular decompression for trigeminal neuralgia, 23 patients undergoing radiofrequency rhizotomy, 15 patients undergoing cerebellopontine tumor resection and one patient undergoing trigeminal schwannoma resection were included. This novel electrophysiologic reflex was noted in all patients with trigeminal neuralgia. The reflex corresponded to the distribution of the pain pattern. (A) Pre-MVD reflex. (B) Post-MVD, the reflex dissipates. (C) Reflex prevalence and BNI pain score. (A) Pre-rhizotomy reflex. (B) Post-rhizotomy, the reflex dissipates. (C) Reflex prevalence and BNI pain score. For radiofrequency rhizotomy, a total of 38 procedures were performed in 23 patients. Of these, 15 were revision procedures. Patients had improvement from BNI pain scale 3.8 ± 0.8 to 1.3 ± 1.5, and had a reduction in number of medications from 1.9 ± 1.0 to 0.8 ±0.9. CONCLUSIONS: A novel, not previously discovered, trigeminotrigeminal and trigeminofacial reflex is present in the pathologic state of trigeminal neuralgia but not in the non-pathologic trigeminal nerve. Radiofrequency rhizotomy can be performed under GA using this reflex as guidance with good results.