Can intraoperative facial nerve motor evoked potential monitoring predict postoperative facial synkinesis following vestibular schwannoma surgery? A retrospective study.

BACKGROUND

Facial synkinesis is a distressing late-onset complication of vestibular schwannoma (VS) surgery. The current study aimed to explore the predictive value of intraoperative facial nerve motor evoked potential (FNMEP) monitoring for postoperative facial synkinesis in VS patients.

METHODS

The data of 170 VS patients were retrospectively analyzed. The final-to-baseline amplitude ratio (FBR) of mentalis FNMEP was selected as a representative metric to assess FNMEP alterations before and after tumor resection. The presence of facial synkinesis was evaluated one year after surgery. Group comparison and logistic regression analysis were performed to assess the predictive value of mentalis FBR for synkinesis. A predictive nomogram was subsequently established. The optimal FBR threshold for predicting synkinesis was obtained by the receiver operating characteristic curve analysis.

RESULTS

Among the cohort, 44.12% (75/170) of patients developed postoperative facial synkinesis. Patients with synkinesis showed higher FBR (p < 0.001) and in-hospital House-Brackmann (HB) grades (p < 0.001). Moreover, both FBR (Odds Ratio 1.107, p < 0.001) and in-hospital HB grade (Odds Ratio 1.731, p < 0.001) were identified as independent predictors for synkinesis. The constructed nomogram showed good calibration and net benefit. The optimal FBR threshold for predicting postoperative facial synkinesis was 11.42% (p < 0.001).

CONCLUSIONS

The FBR of mentalis FNMEP was identified as an independent indicator for the risk of postoperative facial synkinesis. A corresponding predictive model with good predictive performance and significant clinical applicability was developed. Furthermore, a two-step warning strategy for FNMEP monitoring was proposed.