Pre-operative and per-operative factors conditioning long-term facial nerve function in vestibular schwannoma surgery through translabyrinthine approach.

Facial nerve function was evaluated in 103 patients, after vestibular schwannoma removal through the translabyrinthine approach. The mean follow-up was 43 months (minimum six months). Grade I facial function was achieved in 100 per cent of stage I schwannomata compared with 36 per cent of stage IV schwannomata. Grade I or II facial function was found in 78 per cent of homogeneous schwannomata, compared with 48 per cent of heterogeneous schwannomata. Facial function was preserved in 89 per cent of cases, if the angle between the internal auditory canal and the schwannoma was > 66 degrees, compared with 54 per cent if the angle was < 66 degrees. There was 82 per cent of normal facial function when the nerve appeared normal after tumour removal, compared with 18 per cent when the nerve was traumatized. When the ratio (stimulation threshold at the internal auditory canal/stimulation threshold at brainstem) was < 2, post-operative facial function was preserved in 87 per cent of cases, compared with 13 per cent when the ratio was > 2.