Prognostic significance of changes in the internal acoustic meatus caused by vestibular schwannoma.

The prognostic significance of the variety of changes in the internal auditory meatus (IAM) caused by vestibular schwannoma was retrospectively analyzed in 69 consecutive patients with vestibular schwannoma. Preoperative bone-window computed tomography was used to classify IAM changes into extensive destruction (17%), widening (46%), and normal IAM (36%). Extensive destruction (47 +/- 19 years) and widening (48 +/- 13) occurred in significantly younger patients than normal IAM (59 +/- 9). Preoperative hearing was significantly more severely disturbed in patients with extensive destruction than in those with widening or normal IAM. IAM change was significantly related to the tumor consistency, as normal IAM was more common in patients with cystic tumor than in those with solid tumor. Postoperative hearing and facial function were worse in patients with severe IAM change, although the relationship between the IAM change and the surgical result was not significant. One patient with extensive destruction developed postoperative cerebrospinal fluid (CSF) leakage through the air cells around the IAM, and needed surgical repair. Severe IAM change occurs with solid tumor and causes severely disturbed preoperative hearing in younger patients, which reflects the tumor aggressiveness. Severe IAM change increases the technical difficulty of tumor removal and the risk of postoperative CSF leakage, and is associated with a poorer prognosis for patients with vestibular schwannoma.