Intraoperative Visual Evoked Potentials and Electroretinographic Monitoring during Endoscopic Transsphenoidal Surgery

Continuous monitoring of visual function during endoscopic transsphenoidal surgery (ETS) may help prevent damage to the optic apparatus, but the efficacy and feasibility of measuring a visual evoked potential (VEP) remains poorly understood. What is the feasibility, safety, and clinical utility of combined VEPs and electroretinography (ERG) monitoring during ETS? A database of 61 patients (122 eyes) receiving ETS was analyzed. VEPs were classified as robust or non-robust at baseline, with robustness defined by a consistent VEP morphology at start of surgery. A generalized linear-mixed model (GLMM) identified predictors of VEP robustness. Intraoperative VEP changes, effects of sevoflurane anesthesia, complications, and postoperative visual outcomes were assessed. Of 122 eyes, 88 had robust ERGs, of which 68/88 (77%) exhibited robust VEPs. The Oz-Cz scalp channel was the most reliable for interpreting VEPs. The GLMM revealed preoperative visual deficits significantly predicted VEP robustness ( p=0.034 ), while age, sex, tumor size, and chiasmal compression were not predictive. Intraoperative VEP loss during fat graft placement was observed in three patients (six eyes) and resolved after graft removal, without postoperative visual deficits. Sevoflurane anesthesia induced transient loss of intraoperative VEP signal in 71% of cases. No complications related to the monitoring procedure occurred, and no new visual deficits were observed postoperatively in patients with robust baseline signals. VEP monitoring was feasible and safe, while providing real time-feedback that enabled corrective surgical maneuvers during critical steps. Careful patient selection and anesthesia management are essential to maximize efficacy of monitoring and potential clinical benefit. • VEP monitoring during transsphenoidal surgery was feasible in 77% of eyes with robust ERG signals • Preoperative visual deficits significantly predicted non-robust baseline VEPs • Sevoflurane was associated with transient VEP signal loss in 71% of cases during surgery • Fat graft overpacking caused reversible VEP loss in 3 patients, corrected intraoperatively • No monitoring-related complications or new postoperative visual deficits occurred