The usefulness of intraoperative extraocular cranial nerves’ monitoring using the percutaneous needle insertion method by the free-hand technique

Intraoperative neurophysiologic monitoring (INM) is effective method to prevent operation-related nerve damage in various kinds of neurosurgery. In skull base surgery, there a possibility iatrogenic extraocular cranial nerves (EOCNs), which can be prevented with proper INM. We report case chondroma involving clivus and compressing pons who had intraoperative EOCN using the percutaneous needle insertion during extended endoscopic transsphenoidal approach for resection tumor. During tumor removal, structure suspected being right abducens was exposed, it confirmed that electromyography activity generated from lateral rectus muscle by applying electrical stimulation this structure. Postoperatively, patient no diplopia. Our supports could useful assessment function surgery.