Evaluation of the Predictive Value of Intraoperative Changes in Motor-Evoked Potentials of Caudal Cranial Nerves for the Postoperative Functional Outcome

Abstract

Objective: The predictive value of changes in intraoperatively acquired motor-evoked potentials (MEPs) of the lower cranial nerves (LCN) IX-X (glossopharyngeal-vagus nerve) and CN XII (hypoglossal nerve) on operative outcomes was investigated.

Methods: MEPs of CN IX-X and CN XII were recorded intraoperatively in 63 patients undergoing surgery of the posterior cranial fossa. We correlated the changes of the MEPs with postoperative nerve function.

Results: For CN IX-X, we found a correlation between the amplitude of the MEP ratio and uvula deviation (P = 0.028) and the amplitude duration of the MEP and gag reflex function (P = 0.027). Patients with an MEP ratio of the glossopharyngeal-vagus amplitude ≤1.47 μV had a 3.4 times increased risk of developing a uvula deviation. Patients with a final MEP duration of the CN IX-X ≤11.6 milliseconds had a 3.6 times increased risk for their gag reflex to become extinct.

Conclusions: Our study greatly contributes to the current knowledge of intraoperative MEPs as a predictor for postoperative cranial nerve function. We were able to extent previous findings on MEP values of the facial nerve on postoperative nerve function to 3 additional cranial nerves. Finding reliable predictors for postoperative nerve function is of great importance to the overall quality of life for a patient undergoing surgery of the posterior cranial fossa.

Keywords: Glossopharyngeal-vagus nerve; Hypoglossal nerve; Intraoperative neuromonitoring; Motor-evoked potentials; Posterior fossa tumors; Postoperative nerve function.