Intraoperative visual evoked potential has no association with postoperative visual outcomes in transsphenoidal surgery

The aim of this study was to elucidate the relationship between changes in the intraoperative visual evoked potential (VEP) waveform and postoperative visual functional outcomes. Between February 2009 and December 2010, we performed endoscopic endonasal transsphenoidal surgery for sellar or perisellar lesions in 65 consecutive patients with intraoperative VEP monitoring using scalp electrodes under total venous anesthesia. Among the 65 patients, 53 patients were followed-up with postoperative visual function evaluation. VEP waveforms measured at baseline were compared with those obtained toward the end of surgery and the association between changes in VEP waveforms and visual outcomes measured preoperatively and postoperatively were assessed. Reproducible waveforms were obtained intraoperatively in 95 of 106 eyes (89.6%). Of the 95 eyes with reproducible VEP, 64 eyes had stable VEP during the surgery, 19 eyes showed VEP improvement, and 12 eyes had VEP deterioration. Of 64 eyes with a stable VEP, 42 showed no change in visual acuity postoperatively, 13 manifested improvement, and 9 worsened. Of 19 eyes with intraoperative VEP improvement, 13 exhibited no change, 4 improved, and 2 worsened postoperatively. Among 12 eyes with VEP deterioration, just 2 eyes showed visual worsening while the other 10 did not change or improved. Postoperative visual evaluation revealed no light perception in 2 eyes whose intraoperative VEP waveforms were stable throughout the surgery. Intraoperative monitoring of VEP with scalp electrodes under total venous anesthesia had a reproducibility of 89.6% during transsphenoidal surgery for sellar or perisellar lesions. However, the intraoperative VEP waveforms showed no association with postoperative visual outcomes.