Intratumoral continuous facial nerve stimulation for surgical resection of cystic vestibular schwannoma: Technical note

Background: Cystic vestibular schwannomas (CVSs) account for about 10% of VS. The efficacy of continuous facial nerve stimulation (CFS) was previously reported; however, it is often difficult to place the electrode at the root exit zone (REZ) in the early stage of surgical resection. We proposed a new method of intratumoral CFS (ICFS) by searching for the facial nerve through the cyst wall and leaving the spherically shaped electrode at this point. Methods: The cyst wall was opened, and the ventral side of the tumor wall was stimulated to search for the positive point of facial nerve stimulation and place the spherically shaped electrode for continuous stimulation at this point through the cyst cavity (intensity: 0.2–1.5 mA, frequency: 1 Hz). Safe surgical resection could be performed under ICFS in all three cases. Results: Good preservation of the facial nerve and extent of resection that was estimated preoperatively was achieved in all cases. Conclusion: ICFS is suitable for the preservation of facial nerve function in surgical resection of CVS in cases in which electrode placement at the REZ is difficult.