No abstract

Background Transsphenoidal surgery is the gold standard for pituitary adenoma resection. Although rare, a serious complication of surgery is worsened vision post-operatively. Objective To 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. Methods The PubMed and OVID platforms were searched between January 1993 and December 2020 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. Results Eleven studies were included comprising ten case series and one prospective 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. Conclusions Despite 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.

Surgery to the nervous system poses risks to neural structures be that mechanical, haemodynamical, chemical or thermal. The role of intraoperative neurophysiological monitoring (IONM) is to facilitate the assessment of the functional integrity of neural structures and provide a real time alerting system when changes caused by surgically induced insults are detected, with the goal of reducing the risk of postoperative neurological deficits. Furthermore, it is also used as a guidance system to map eloquent areas within the cortex and to identify specific neuronal structures, particularly when landmarks cannot be easily recognized. In this article, we focus on the various neurophysiological modalities used in intraoperative monitoring, their basic principles, indications and the information that they provide. We also examine the anaesthetic considerations and the checklist for the multidisciplinary team should an intraoperative alert be issued.

No abstract