Intraoperative Monitoring of Visual Evoked Potentials in Patients Undergoing Transsphenoidal Surgery for Pituitary Adenoma: A Systematic Review
Abstract BackgroundTranssphenoidal surgery is the gold standard for pituitary adenoma resection. Although rare, a serious complication of surgery is worsened vision post-operatively. ObjectiveTo determine whether, in patients undergoing transsphenoidal surgery for pituitary adenoma, intraoperative monitoring of visual evoked potentials (VEP) is a safe, reproducible and effective technological adjunct in predicting postoperative visual function. MethodsThe MEDLINE database was searched between January 1993 and June 2019 to identify publications that (1) featured patients undergoing transsphenoidal surgery for pituitary adenoma, (2) used intraoperative optic nerve monitoring with VEP and (3) reported on safety or effectiveness. Reference lists were cross-checked and expert opinion sought to identify further publications. ResultsTen studies were included comprising nine case series and one cohort study. All employed techniques to improve reliability. No safety issues were reported. The only comparative study included described a statistically significant improvement in post-operative visual field testing when VEP monitoring was used. The remaining case-series varied in conclusion. In nine studies, surgical manipulation was halted in the event of a VEP amplitude decrease suggesting a widespread consensus that this is a warning sign of injury to the anterior optic apparatus. ConclusionsDespite limited and low-quality published evidence regarding intra-operative VEP monitoring, our review suggests that it is a safe, reproducible and increasingly effective technique of predicting postoperative visual deficits. Further studies specific to transsphenoidal surgery are required to determine its utility in protecting visual function in the resection of complex pituitary tumours, and of other tumours in the anterior skull base.