PREOPERATIVE AND PEROPERATIVE 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 fo llow-up was 43 months (minimum six months). Grade I facial function wa s achieved in 100 per cent of stage I schwannomata compared with 36 pe r cent of stage IV schwannomata. Grade I or II facial function was fou nd in 78 per cent of homogeneous schwannomata. compared with 48 per ce nt of heterogeneous schwannomata. Facial function was preserved in 89 per cent of cases, if the angle between the internal auditory canal an d the schwannoma was > 66 degrees, compared with 54 per cent if the an gle 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 t hreshold at the internal auditory canal/stimulation threshold at brain stem) was < 2, postoperative facial function was preserved in 87 per c ent of cases, compared with 13 per cent when the ratio was > 2.