• Giuseppe Maria Della Pepa, Flavia Fraschetti, DomenicoMichele DiMD1Department of Neurosurgery, A. Gemelli University Hospital Foundation IRCCS, Catholic University of the Sacred Heart, Rome., Angelica Valz Gris, Alessandro Izzo, Grazia Menna, Quintino Giorgio D'Alessandris, Manuela D'Ercole, Vito Stifano, Carolina Ausili Cefaro, Liverana Lauretti, Gianpiero Tamburrini, Alessandro Olivi, and Nicola Montano.
• 1Department of Neurosurgery, A. Gemelli University Hospital Foundation IRCCS, Catholic University of the Sacred Heart, Rome.
• J. Neurosurg. 2024 Jun 1; 140 (6): 154015481540-1548.

ObjectiveDysphagia is a significant complication in fourth ventricle surgery. Corticobulbar motor evoked potentials (CB-MEPs) of the lower cranial nerves may provide real-time information possibly correlating with postoperative swallowing dysfunction, and the vagus nerves may prove ideal for this purpose. However, the literature is heterogeneous, non-systematic, and inconclusive on this topic. The object of this retrospective study was to evaluate the correlation between CB-MEPs of the vagus nerve and postoperative worsening or new-onset swallowing deficits in intraaxial fourth ventricle surgery.MethodsIn 21 consecutive patients undergoing surgery for fourth ventricle intraaxial tumors between February 2018 and October 2022, endotracheal tubes with two applied electrodes contacting the vocal cords were used to record vagus nerve MEPs including values at baseline, the end of surgery, and the minimum value during the operation. From the mean value of right and left vagus nerve MEP amplitudes, the minimum-to-baseline amplitude ratio (MBR) and final-to-baseline amplitude ratio (FBR) were calculated. These indexes were correlated with postoperative swallowing function.ResultsGiven their clinical significance, receiver operating characteristic curves were obtained to evaluate the performance of these indexes in predicting postoperative swallowing function. The area under the curve (AUC) was 0.850 (p < 0.001) and the best cutoff for FBR was 67.55% for the worsening of swallowing in the postoperative period. The AUC was 0.750 (p = 0.026) and the best cutoff was 46.37% in MBR for the absence of a swallowing disorder at the late follow-up.ConclusionsThis study confirmed that vagus nerve MEPs are reliable predictors of postoperative swallowing function in fourth ventricle surgery and can be feasibly used as an intraoperative monitoring technique.

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