Intraoperative neurophysiological monitoring of facial nerve in vestibular schwannoma surgery: experience of the Burnasian Federal Medical Biophysical Center

Background. Large vestibular schwannomas can not only change the anatomy and structure of the facial nerve in the process of growth, but also encapsulate it over a considerable length. Despite the development of modern neurosurgical techniques and achievements in the field of microscopy, it is often impossible to avoid damage to its integrity during the separation of the facial nerve, which is associated with the development of paresis of the facial muscles in the postoperative period. The use of intraoperative neurophysiological monitoring in surgery for vestibular schwannomas pursues the following tasks: identification of neural structures, timely detection of signs of their damage, and prevention of iatrogenic neurological deficit. Aim. To analyze the results of microsurgical removal of vestibular schwannomas using intraoperative neurophysiological monitoring. Materials and methods. A series of clinical cases of patients who underwent microsurgical removal of sporadic vestibular schwannomas using suboccipital retrosigmoid transmeatal access under the control of multimodal intraoperative neurophysiological monitoring is presented. Neurological assessment of the facial nerve function was carried out in the early postoperative period and 3 months after surgical treatment using the House–Brackmann scale. Results. Postoperative results of surgical treatment were collected in 11 patients. According to the results of the neurological assessment in the early postoperative period, the result was regarded as successful in 5 cases, satisfactory in 3 cases, and poor in 3 cases (grade V on the House–Brackmann scale). The use of direct monopolar stimulation technique made it possible to identify the location and course of the facial nerve with high accuracy in all patients. In 2 cases, the tumor was resected subtotally due to the appearance of neurophysiological predictors of facial nerve dysfunction. Conclusion. The use of multimodal neurophysiological monitoring when removing large vestibular schwannomas can make surgical treatment more controllable and thus indirectly affect functional outcomes.