[Intraoperative Electrophysiological Monitoring for Neurosurgery]

Both motor evoked potential (MEP) and somatosensory evoked potential (SEP) have been used for the purpose of preventing postoperative neurological complications in patients undergoing neurosurgery. Although not completely, they can detect insufficient cerebral blood flow during aneurysm surgery and carotid surgery and prevent functional deterioration during tumor resection. Regarding MEP, there are several points to be considered for maximizing the potential of MEP. First, suprathreshold stimulus should be used because supramaximal stimulus may be too strong, resulting in false negative responses. Second, direct cortical stimulation in addition to transcranial stimulation may be useful for stimulating the target area precisely. Third, subcortical stimulation can provide decisive information during tumor resection. Although there is no such thing as 100% accuracy in electrophysiological monitoring, a multimodal electrophysiological monitoring system may contribute to decrease neurological deficits. Irreversible neurological deficits could be prevented by early detection of the changes in the amplitude and by prompt intervention to correct deteriorating condition. Therefore, it is important for anesthesiologists to select suitable anesthetics for the monitoring, maintain the depth of anesthesia, and discuss the patient management with surgeons.