Facial Nerve Preservation in Surgery of T3 and T4 Vestibular Schwannomas

Objective: In vestibular schwannoma (VS), treatment for functional facial nerve preservation is of major importance.

Design: Clinical data, surgical and monitoring techniques, and their impact on functional outcome were the focus of this study.

Patients and Methods: Out of a consecutive series of 1700 patients treated for VS at the Head and Neck University Clinic, the most recent 270 patients with VS extensions T3 (partial or complete filling of the cistern) and T4 (brainstem compression) were analyzed after retrosigmoid resection under conventional EMG monitoring and additional motor-evoked potentials (MEPs). Early postoperative facial nerve function was evaluated by House-Brackmann-Scale (HB) and related to tumor extension, microsurgical findings, technique, and monitoring results.

Results: In T3 and T4 tumors, anatomical facial nerve preservation was achieved in 96% and nerve reconstruction was necessary in 4%. Early good function HB 1 to 3 was present in 78% of patients. Rates of good early function have increased recently to 86% along with the MEP application. Patients' age and sequence of surgical steps were not relevant factors. Positive predictors of good function were normal preoperative facial function and postoperative hearing preservation. Strong tumor adherence with the facial nerve did not impair preservation, but adherence with the brainstem was a negative sign.

Conclusions: In medium to large VS sizes, identification and preservation of the facial nerve are more difficult. Preservation rates are improved, nonetheless, by meticulous microsurgical technique and feedback of facial MEP reflecting the integrity of the complete motor pathway.