Intraoperative neurophysiological monitoring (IONM) has been widely used to detect iatrogenic neural damage to minimize postoperative neurological deterioration. In this case, a damage was prevented by early detection of the improper position and by a correction of marked drops in blood pressure through IONM. A 72-year-old man underwent surgery due to cervical myelopathy. The somatosensory evoked potentials (SEPs) in bilateral median nerves showed prolongation of latency and reduction of amplitude. It was suspected that the cervical spine was excessively flexed by traction, and all tractions were released. In addition, the mean blood pressure was lowered to 53 mmHg, and it was confirmed that the infusion line and the SEP electrode were compressed in the right wrist. After decompression, bilateral median SEPs were recovered, and there was no postoperative neurological deterioration. Thus, IONM is useful in identifying early evidence of neural insult which may be caused by improper positioning during surgery.