O178 Correlation between postoperative visual outcome and intraoperative visual evoked potentials during endoscopic transsphenoidal surgery

Abstract

Objective We evaluated intraoperative changes in VEP waveforms to clarify the predictive criteria and limitations of intraoperative monitoring using VEPs. Methods Between April 2008 and June 2016, we analyzed VEP data obtained from 35 patients who developed visual dysfunction and underwent endoscopic TSS for non-functioning pituitary adenomas. For all patients, we attempted to record intraoperative VEPs for each eye by stimulating with a light-emitting device placed over the eye. Results We obtained 68 VEP recordings from affected eyes in 35 operations. Along the decompressive surgical stage, N75-P100 amplitude gradually increased, but not P100 latency. N75-P100 amplitude increase greater than 50% correlated with an improvement in postoperative visual acuity. However, visual field recovery did not correlate with the changes in VEP waveform. Discussion These findings indicate the intraoperative change of N75-P100 amplitude predicted the postoperative improvement of visual acuity. In this study, we obtained stable and reproducible waveforms. Conclusions Intraoperative VEP monitoring for procedures performed around the anterior visual pathway can detect either visual improvement or deterioration. N75-P100 amplitude changes greater than 50% can indicate changes in visual acuity, but do not predict changes in the visual field. We hypothesized that postoperative visual improvement may correlate with improvement of VEP amplitude before our analysis. These findings can be adapted for transcranial surgery or extended TSS for tumors around the anterior visual pathway.