gms | German Medical Science

Objective: In vestibular schwannoma (VS) treatment functional facial nerve preservation is the most important goal for most patients. Clinical data, surgical and monitoring techniques and their impact on functional outcome were the focus of this study.

Method: 266 patients with normal pre-operative facial nerve function were selected for analysis out of a consecutive series of vestibular schwannomas. All underwent microsurgical tumour resection under conventional electromyography monitoring and, in the most recent 107 patients, additional motor evoked potentials (MEP) of the facial nerve. Facial nerve function was evaluated by House-Brackmann-Scale (HB) and photo documented before surgery, after surgery at demission and at 12 months follow-up. Outcome was summarized as useful in case of complete eye closure HB°1 to °3, and as non-useful in missing or incomplete eye closure HB°4 to °6. Outcome was related to tumour extension, microsurgical findings and monitoring technique.

Results: Anatomical facial nerve preservation was achieved in 96% and nerve reconstruction was necessary in 4%. Early useful function HB°1 to °3 was present in 82% of patients and increased to 95% within the first year of follow-up. In the sub-group of large tumours with broad brainstem contact or brainstem compression early useful function was obtained in 78%. In the sub-group of 107 patients monitored with MEP, rates of useful early function have increased significantly to 86% (p<0.01%). Patients’ age and the sequence of surgical manoeuvres were no relevant factors. Positive predictors of useful function were normal pre-operative facial function and post-operative hearing preservation. Strong tumour adherence with the facial nerve did not impair the preservation, but adherence with the brainstem was a negative indicator.

Conclusions: In tumour extensions with broad brainstem contact the identification and preservation of the facial nerve is more difficult. By combining conventional EMG monitoring with MEP, continuous information on the complete motor pathway of the facial nerve becomes possible even without direct nerve visualization. This feedback during meticulous microsurgical resection is a reliable support and directive for the continuation or change of the surgical procedure. Thereby, the rates of functional facial nerve preservation are further improved.