Some experience of neurophysiological monitoring in neurosurgery

Aim. This retrospective study is aimed at evaluating the efficacy of neuromonitoring methods to prevent postoperative neurological complications and estimating predictive power of intraoperative changes in monitored characteristics. Methods. 240 patients operated over a period from 2014 to 2015 underwent intraoperative neurophysiological monitoring. 173 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 and transcranial motor potentials were controlled in 36 cases. Stimulation mapping of motor cortex was performed in 69 surgeries and cranial nerves identification - in 27. The electrocorticogram was registered in 7 patients, with 3 of them undergoing intraoperative awakening for speech function mapping. Results. The sensitivity of SSEP in detection of motor dysfunctions was low (33%), while the specificity tended to be relatively high (82%). These characteristics for visual and motor evoked potentials were close to 100% provided the parameters of the anesthesia met the relevant requirements. As for prevention of postoperative dysfunctions, the most effective methods were stimulation mapping of functionally significant areas (motor and speech ones) and motor pathways mapping. Conclusion. Intraoperative neuromonitoring reduces the occurrence rate of neurological complications after neurosurgical operations. The SSEP method is not sensitive enough in surgeries that could affect motor centers and/or pathways, therefore, multimodal monitoring which combines SSEP and motor responses registration during transcranial and/or direct electrical brain stimulation is needed. Successful monitoring requires efficient cooperation of neurophysiologists, neurosurgeons and anesthesiologists.