Aim: Although studies on monitoring modalities have been previously conducted, they have shown differences in the values of preoperative and intraoperative monitoring. This study sought to compare preoperative and intraoperative electrophysiologic values.Material and Methods: A retrospective medical record review was conducted on patients who underwent brain and spine surgery between January 2014 and July 2018. Patients underwent preoperative electrophysiologic monitoring within a week before the operation and intraoperative monitoring during the surgery. Monitoring parameters included the onset latency (msec) and amplitude (mV) of motor evoked potential (MEP), somatosensory evoked potential (SEP), electroneuronography, and brainstem auditory evoked potential (BAEP).Results: The latency of the MEP and SEP were significantly prolonged while the amplitude was decreased during operation. Specifically, patients with abnormal findings in their preoperative assessments showed more prominent differences compared to those with normal findings. However, there was no significant difference between preoperative and intraoperative results based on which side of the hemisphere was affected or unaffected. Unlike the MEP and SEP parameters, there were no significant changes in the facial electroneuronography and BAEP parameters.Conclusion: There were differences in the preoperative and intraoperative monitoring parameters. Further studies are necessary to understand the underlying mechanisms behind these changes during surgery.