Prognostic Factors for Facial Nerve Preservation in Vestibular Schwannoma Surgery

Introduction: Facial nerve preservation in vestibular schwannoma surgery mainly depends on the size of the lesion and the extent of resection. Other variables, like peritumoral adhesions, tumor vascularization, and facial nerve trajectory, may also play a role, making their preoperative identification important to optimize nerve preservation rate.

Objective: To analyze the radiological characteristics of these variables, correlating intraoperative, histopathological and molecular findings to postoperative facial nerve function results.

Materials and Methods Our series included 78 patients with sporadic vestibular schwannomas. T2-FSE/FIESTA magnetic resonance sequences were performed for evaluation of facial nerve trajectory and peritumoral dissection plane. Perfusion sequences were obtained for tumor vascularization. Intraoperatively, facial nerve location, types of peritumoral adhesions and bleeding characteristics were registered. Postoperative short- and long-term facial function was evaluated during follow-up using House-Brackmann scale. Pathology exam reported on microvascular density, adhesion characteristics (metalloproteinases 2-9, E-caderines, and CD44), and presence of vascularization promoting (VEGF) factors.

Results: Anteroinferior facial nerve trajectory increased more chances of good facial results sevenfold compared with the anterosuperior location. Perilesional adhesion imaging helped predict peritumor dissection plane. Presence of peritumor cleft on FSE-T2 and FIESTA sequences increased chances of identifying a good intraoperative plane, 5.2 and 3.6-fold, respectively. Postoperative facial function was significantly associated with FIESTA sequence findings. Molecular analysis showed higher values of E-caderines in tumors without peritumor cleft on FIESTA sequences, and although not statistically significant, a trend toward higher CD44 values in schwannomas with good peritumor dissection plane was observed. We found no association between grade of vascularization on perfusion sequences and degree of intraoperative bleeding. Nor was there any relationship between these variables and VEGF levels. Postoperative facial function showed no correlation with grade of vascularization on perfusion sequences. Vestibular schwannomas with mild intraoperative bleeding showed a trend toward better postoperative facial function, although not statistically significant. Hypervascular lesions on perfusion sequences showed slight increase in microvessel density (CD34) again, not statistically significance.

Conclusions: Our results suggest facial nerve trajectory and peritumoral adhesions are prognostic factors of facial nerve preservation in vestibular schwannoma surgery. Although we were unable to show a direct association with respect to degree of tumor vascularization, a trend was observed, which would require further investigation.

Fig. 1 Female patient 65 years old with a right-side vestibular schwannoma grade 4a. (A) T1 sequence after contrast; (B) T2 sequence showing the peritumoral dissection plane; (C) FIESTA sequence; (D) intraoperative picture; (E) postoperative T1 sequence after contrast; (F) postoperative facial nerve status House-Brackmann II.

Fig. 2 Male patient of 44-year-old with a right-side vestibular schwannoma grade 4a. (A) T1 sequence after contrast; (B) perfusion sequence; (C) FIESTA sequence; (D) VEGF expression; (E) microvascular density (CD34); (F) postoperative facial nerve status House-Brackmann 5.

Publication History

Article published online:
01 February 2023