Internal Neurolysis for Trigeminal Neuralgia: A Preliminary Single-institution Experience in Japan

Internal neurolysis (IN) is a surgical procedure in which the trigeminal fibers are separated between the pons and porus trigeminus to relieve trigeminal neuralgia (TN). Recent investigations revealed that the number of nerve bundles made by IN varies, and immediate postoperative hypesthesia exceeded 90% and pain control rate at 1 year was 77%-93.5%. We present the preliminary experience of 18 patients who underwent IN for TN between June 2020 and June 2022. The Barrow Neurological Institute pain scale (BNI-PS) was recorded preoperatively and in June 2023, and the Barrow Neurological Institute hypesthesia scale (BNI-HS) was recorded preoperatively, immediate postoperatively and in June 2023. Intraoperatively, the number of bundles made by IN was reviewed. Preoperative BNI-PS ranged between VI and V. Two patients experienced BNI-HS II due to percutaneous procedure prior to IN. Intraoperatively, 3 bundles were made by IN in 7 patients, 4 bundles in 5, and 5 bundles in 6. Immediate postoperative BNI-HS I was recorded in 6 patients and II in 12 (66.7%). The last follow-up revealed that BNI-PS I and II were recorded in 13 patients (72.2%) and BNI-HS I and II in 6 patients, respectively. Our results demonstrated that the rates of immediate postoperative hypesthesia (66.7%) and pain control (72.2%) at 1 year or later were below those of previous reports. Therefore, we are currently combing to make at least 6 bundles. Detailed surgical technique and cardiac reflex alerts during the procedure are described.