Distance from acoustic neuroma to fundus and a postoperative facial palsy

Objective/Hypothesis: Generally, patients with small acoustic neuroma have less facial palsy after its removal. The middle cranial fossa approach is mainly applied to the small acoustic neuroma and tumor size does not influence the prognosis of facial palsy. The internal auditory canal cannot be fully opened in the middle cranial fossa approach, and the facial nerve is tightly attached in the fundus. According to these anatomical factors, we hypothesized that acoustic neuroma located away from the fundus might be removed with less facial nerve damage. We investigated the distance between the acoustic neuroma and fundus and its clinical relationship. Study Design: Retrospective study of 45 patients with acoustic neuroma who underwent a middle cranial fossa approach. Methods: The distance between the acoustic neuroma and fundus and the tumor diameter were measured on T2-weighted and contrast-enhanced magnetic resonance images, respectively. These data were compared with the postoperative facial nerve function. Results: The mean distance was 3.0 +/- 1.8 mm (range, 0-10 mm), and the mean diameter was 11.3 +/- 3.7 mm (means +/- standard deviation; range, 4-20 mm). Neither the distance nor the diameter had any correlation to the degrees of postoperative facial palsy either immediately or at 3 months after surgery. Conclusions: As far as the nerve was anatomically preserved, postoperative facial nerve function seemed to be influenced by factors other than surgical manipulation among small acoustic neuromas. Although the tumor fills in the fundus, it may not influence postoperative facial nerve function and also may not interfere with indication of the middle cranial fossa approach for removal of the acoustic neuroma.