Platform Session – Evoked potentials & NIOM: Prognostic value of intra- and extra-operative lateral spread responses in microvascular decompression surgeries of hemifacial spasm

Abstract

Introduction Lateral spread response is observed in patients with hemifacial spasm (HFS) by eletrically stimulating one branch of the facial nerve activates facial muscles innervated by other branches of the facial nerve by electromyography. Nowadays, LSR has been used to confirm adequacy of microvascular decompression (MVD). The aim of this study was to evaluate the prognostic value of intra- and extra-operative lateral spread response (LSR) in microvascular decompression (MVD) surgeries of hemifacial spasm (HFS). Methods A retrospective review was made of consecutive 25 patients who underwent continuous intraoperative monitoring during MVD. LSR and continuous electromyography were monitored in the frontalis, orbicularis oculi, and mentalis muscles. Extra-operative LSRs were done pre- and postoperatively. The neurological status of each patient was evaluated before and immediately after surgery, on discharge, and at 3 months after surgery. Results Intraoperative neurophysiologic monitorings were successful in all patients. On admission and discharge, extra-operative LSR recordings were done in 23 patients. Twenty-one patients completed a follow- up evaluation. In 17, the intraoperative LSRs disappeared during surgery. In 5, the intraoperative LSRs were absent before incision and remained the same until the end of surgery. In one, the intraoperative LSR were present before incision and persisted despite MVD. For extra-operative LSRs, they disappeared after surgery in 10. LSRs were absent before and after surgery in 7. In 6, LSRs were present before surgery and persisted after MVD. For 5, intraoperative LSRs disappeared during surgery but extra-operative LSRs were persisted despite adequate MVD. In one, intraoperative LSRs were absent before incision and remained during the surgery. But extra-operative LSRs were present before surgery and disappeared after adequate MVD. Statistically, the extra-operative disappearance of LSR was correlated with the HFS relief in 4 days after surgery and the 3-month follow up period. (P = 0.049 and 0.044). However, the intaroperative disapearance of LSR was not. Conclusion In our study, extra-operative LSR monitoring may be more predictive of the surgical outcome compared with intraoperative LSR during the 3-month follow up.