Trigger electromyography in endoscopic transnasal surgery of the skull base tumors

Preserving anatomical integrity and functions of cranial nerves when removing skull base tumors is one of the significant problems of endoscopic endonasal surgery. For this purpose, it is possible to use intraoperative mapping and cranial nerves identification. The aim of the study was to evaluatе the effectiveness of trigger electromyography (T-EMG) used to prevent iatrogenic damage to the cranial nerves intraoperatively. Twenty-one patients with different skull base tumors were included in the study. Mapping and identification of cranial nerves were carried out during tumor excision, using endoscopic endonasal access. Surgeries were performed on large skull-based chordomas, neuromas of the trigeminal nerve in the cavernous sinus region, pituitary adenomas, meningiomas in the clivus and a skull-based cholesteatoma. Mapping and identification of cranial nerves were carried out using electromyography in trigger mode using bipolar and monopolar electrodes. Functional activity of cranial nerves was evaluated both before and after the operation. The effectiveness of the technique was compared with that of the control group (41 patients). In the course of surgical interventions using T-EMG in the main group of patients, 40 nerves were analyzed. In the course of the study, III, V, VI, VII, XII cranial nerves were identified intraoperatively. In 4 patients in the main group and in 13 patients in the control group, a postoperative deficit of cranial nerves was observed. We did not receive statistically reliable data that the intraoperative identification of cranial nerves using T-EMG reduces the frequency of postoperative complications in the form of a deficiency of cranial nerves (p=0.11), but the ratio of chances (0.26) testifies in favor of rarely occurring complications in main group. Trigger electromyography allows us to estimate the functional state of the cranial nerves during endoscopic endonasal operations. The method of using T-EMG is promising and requires further research.