83. Intraoperative visual evoked potentials: A study in pituitary microadenoma surgery

Abstract

Conflicting reports on the usefulness of intraoperative monitoring of visual function by means of visual evoked potentials (VEPs) are reported. In order to verify the real usefulness of this method in supporting pituitary surgery, we studied 10 patients with pituitary microadenoma without any visual problems to collect normative data. 10 patients (mean age 50 yrs), undergoing trans-sphenoidal surgery for pituitary microadenomas, were studied with intraoperative VEP monitoring. All patients had a normal pre- and postoperative visual function. ERG responses were recorded in 5 patients, mean latency = 54,11 ms (±3.98 DS). Intraoperative VEPs were recorded in 18 of 20 sides (90%). The variability of N2 latency did not exceed 10% of the baseline value (before surgical manoeuvres, mean = 140.95 ms ± 18.88 SD) and the P2–N2 amplitude variability was less than 50% in all but one patient. Our study confirms that generally VEPs remain stable during microsurgical procedures. Intraoperative VEP recording might be a potentially useful tool in the monitoring of the functional integrity of the posterior visual pathway.