Efficacy of Intraoperative Neurosurgical VEP Monitoring

Abstract

Visual evoked potential (VEP) had not been seemed to be suitable for intraoperative monitoring because of its long latency and needs for addition. Intraoperative visual VEP monitoring under the recent anesthetic and neurophysiological techniques are examined. Since May 2002, VEP monitorings using LED Goggles (1Hz stimulation) by Neuropack MEB2200 (Nihon Koden Co. Ltd.) were performed in 15 neurosurgical operation including 5 transsphenoidal surgery (3 pituitary adenomas and 2 others) and 10 craniotomy (9 brain tumors and an arterio-venous malformation). Propofol anesthesia was performed in 14 operations and an inhalation. Scalp recording with the screw electrodes were monitored in 13 operations, subdural electrodes for direct cortical recording were used in 4, and both 2 methods were used together in 2 operations. Most P100 wave was stably recorded even in intraoperative monitoring. Shorter latency waves in cortical recording than in scalp recording were seemed to be available in intraoperative VEP. In a transsphenoidal surgery for acromegaly, the shortening of the latency after the tumor resection agreed with postoperative improvement of visual symptoms. Intraoperative VEP monitorings were not successful in 5 among 15 operations. LED Goggles was not suitable for intraoperative use and the special light-stimulator for intraoperative monitoring is now prepared.