Posterior fossa meningioma with invasion of the internal acoustic canal.

BACKGROUND: To evaluate the significance for outcome of meningioma invasion into the internal auditory canal (IAC) in posterior fossa meningiomas.

METHODS: From April 2005 to September 2015, 174 posterior fossa meningiomas have been surgically treated in our Institution. Careful analysis of preoperative MRI depicted in 63 cases (36%) meningioma invasion into the IAC. A retrospective analysis was done of clinical and radiological presentation, surgical findings, outcome, and relevant prognostic factors in order to stratify the risk of complication and evaluate the surgical outcome.

RESULTS: Gross total resection was achieved in 67% of patients. There was no mortality. CSF leak occurred in 5%. Postoperative moderately severe (HB 4) and severe dysfunction (HB 5) of the facial nerve was observed in 5% of patients. In 17 patients (27%), IAC was opened. Deterioration of facial function occurred in 24% of patients, hearing loss in 12%, and CSF leak in 6%. In 46 patients (73%), IAC was not opened. Deterioration of facial function occurred in 43% of patients, hearing loss in 13%, and CSF leak in 4%. Opening the IAC, a GTR was achieved in 82% while, without opening, in 61% of patients.

CONCLUSIONS: Meningiomas of the posterior fossa may in one-third of the cases invade the IAC. Opening of the IAC in these cases was a crucial step for increasing the GTR. Despite the minimal increased risk of transient CSF leak, IAC opening was not associated with an increased risk of facial palsy or hearing loss in comparison to non-opening the IAC.