Functional Staging of Acoustic Neuromas

Abstract

Facial function and hearing preservation are the two main challenges in acoustic neuroma surgery. A retrospective study of 441 patients [192 males and 249 females; mean age; 60 years (range, 16–79)] who were operated on for a unilateral acoustic neuroma was undertaken. The mean diameter of the tumors was 26 ± 0.6 mm. One hundred four patients (14%) were operated on through conservative approaches (middle cranial fossa and retrosigmoid) and 335 (76%) through the translabyrinthine route. A cutoff value for the tumor diameter in the cerebellopontine angle (CPA) was observed at 15 mm in terms of postoperative facial and hearing function. Among lesions operated on through conservative approaches, hearing preservation was obtained in 63% and 14% of patients with tumors measuring less than 15 mm and between 16 and 20 mm in the CPA, respectively. The proportion of good facial function 1 year after surgery with tumors between 11 and 15 mm and between 16 and 20 mm was 91% and 73%, respectively. In conclusion, a classification is proposed subdividing the lesions as follows: stage 1, intracanalicular; stage 2, less than 15 mm in the CPA; stage 3, 15–30 mm in the CPA; stage 4, more than 30 mm in the CPA. This classification appears to be well correlated to facial function prognosis and the possibility of hearing function preservation.