Preoperative appearance of facial muscles on magnetic resonance predicts final facial function after acoustic neuroma surgery

Objective: Several previous studies have shown that muscle appearance on magnetic resonance is a sensitive indicator of muscle denervation. Previous attempts at determining preoperative indicators of final facial function after acoustic neuroma removal has been mostly unsuccessful. The goal of this study was to determine if the appearance of the facial muscles on preoperative imaging is predictive of final facial function after surgical removal of vestibular schwannomas. Study Design: We conducted a retrospective chart and magnetic resonance review. Setting: This study was conducted at a tertiary referral center. Patients: We included all patients who underwent vestibular schwannoma removal between January 1, 1997, and December 31, 2001, with available preoperative magnetic resonance images and a minimum of 12 months follow up. Interventions: We used translabyrinthine, middle fossa, and suboccipital approaches for tumor removal. A neuroradiologist, blinded to preoperative or final facial function after tumor removal, retrospectively reviewed preoperative magnetic resonance images. Main Outcomes Measures: Facial muscles were evaluated on magnetic resonance and classified as symmetric or asymmetric. Facial function was graded using the House-Brackmann scale. Preoperative facial function was noted on the preoperative physical examination. Final function was determined at least 12 months postoperatively. Results: A total of 247 patients underwent tumor removal during the study period. One hundred thirty-two patients had adequate preoperative magnetic resonance images. Patients with preoperative facial muscle asymmetry seen on preoperative magnetic resonance indicating muscle atrophy had significantly worse final facial function, regardless of tumor size. Conclusion: The preoperative appearance of facial muscles provides valuable insight into the physiology of the facial nerve in the presence of vestibular schwannomas. Patients with preoperative facial muscle symmetry have significantly better facial function than those with atrophy.