An experience of neurophysiological monitoring in neurosurgery

Abstract

Objective. To evaluate the efficacy of neuromonitoring methods in prevention of postoperative neurological complications and estimation of predictive power of intraoperative changes in monitored characteristics. Material and methods. Retrospective study examined 240 patients, operated in the years 2014—2015 using intraoperative neurophysiological monitoring. One hundred and seventy-three patients suffered from hemispheric lesions and 67 had lesions located in or near the brainstem. Somatosensory evoked potentials (SSEP) were monitored in 152 cases, visual in 32, brainstem acoustic in 22, transcranial motor in 36; stimulation mapping of motor cortex was performed in 69 surgeries, and cranial nerves identification in 27. EEG was recorded in 7 patients, and 3 of them were woke up during the surgery for speech mapping. Results. The sensitivity of the SSEP in motor dysfunction detection was low (33%), while the specificity was relatively high (82%). These characteristics for visual and motor evoked potentials were close to 100% provided that the parameters of anesthesia met the corresponding requirements. The most effective methods in respect of prevention of postoperative dysfunctions were the stimulation mapping of functionally significant areas (motor and speech) and motor pathways mapping. Conclusion. Intraoperative neuromonitoring reduces a number of neurological complications after neurosurgical operations. The SSEP method is not sensitive enough in surgeries that could affect motor centers and/or pathways, and multimodal monitoring combining SSEP and motor responses recording during transcranial and/or direct electrical brain stimulation. Successful monitoring requires highly coordinated actions between neurophysiologists, neurosurgeons and anesthesiologists.