Die Auswirkung der Tumorelongation auf das Ergebnis des Nervus Facialis nach der Operation von Vestibularisschwannomen der Koos-Grade 3 und 4 in halbsitzender Lagerung über den retrosigmoidalen Zugang

Objective: Facial nerve paralysis is a significant and debilitating condition that can arise following surgery for vestibular schwannoma (VS). This study aims to assess the outcomes of facial nerve function by considering various factors such as shape features, extent of resection, baseline tumor volume, and patient-specific characteristics.

Methods: We analyzed 120 sporadic VS patients who underwent surgery in our center from 2012 to 2022. 61 patients were included in the analysis. Inclusion criteria were primary tumor, Koos grade 3 or 4, and available imaging data for radiomic analysis. All included cases were treated in the semi-sitting position via the retrosigmoid approach. Radiomic tumor shape features (elongation, flatness, sphericity), pre- and postoperative tumor volumes, and extent of resection (%) were assessed using 3D Slicer (Version 5.2.1, Surgical Planning Laboratory, Harvard University, USA). Primary endpoint was the facial nerve outcome (FNO) at 3-months after VS surgery. FNO was dichotomized into "good" (House-Brackmann (HB) score ≤2) and "poor" (HB>2).

Results: Poor FNO was observed in 11 patients (18.0%) at 3-months after VS surgery. Radiomic tumor shape features were analyzed and the AUC of elongation in the prediction of a poor HB at 3-months was 0.70 (95% CI: 0.56-0.85, p=0.03) and the optimum threshold value (≤/>0.35) yielded a sensitivity and specificity of 64.0% and 75.4%, respectively. Multivariable logistic regression analyses considering extent of resection (0.35) revealed that more elongated VSs (≤0.35, OR: 5.8, 95%CI: 1.2-28.2, p=0.03) and those with an increased EoR (≥93.4%, OR: 6.5, 95%CI: 1.0-42.5, p=0.05) are independently associated with poorer FNO at 3-months after surgery.

Conclusion: Highly elongated VS shape seem to be a risk factor for worsened facial nerve outcome at 3-months after surgery for Koos grade 3 and 4 tumors. A surgical policy of near total resection might be superior to gross total resection regarding facial nerve preservation in those cases with an elongated tumor shape.