Preservation of facial nerve function in acoustic neuroma surgery by the extended middle cranial fossa approach.

The anatomical preservation rates of the facial nerve and postoperative facial nerve function were investigated in cases of initial operation for acoustic neuroma by the middle cranial fossa or extended middle cranial fossa approach. The cases were divided chronologically into three groups according to the date of surgery. The rate of anatomical preservation was 93% in the most recent period, compared to 82.4% for the entire series. This was attributable to higher preservation rates being achieved in cases with medium or large tumors with increased experience. Also regarding postoperative facial nerve function, the number of cases with no paralysis or only partial paralysis increased and the number of cases requiring sacrifice of the facial nerve decreased as experience was accumulated in the series. Even when the facial nerve was preserved anatomically, however, facial-hypoglossal anastomosis was carried out actively if facial nerve function did not recover satisfactorily one year after surgery. For this reason, as many as 33% of the patients underwent anastomosis. This high percentage, however, is attributable to anastomosis ultimately being carried out in 47.7% of the patients in the early period; 22.2% of the patients in the most recent period underwent anastomosis.