Meningiomas of the cerebellopontine angle with extension into the internal auditory canal

Abstract

Object. Only some meningiomas of the cerebellopontine angle (CPA) extend into the internal auditory canal (IAC) or arise from its dural lining. The authors investigated cases of CPA tumors in which the meningioma was inserted in the dura mater in or at the ICA or infiltrated a cranial nerve. Methods. The authors reviewed patient charts including surgical and clinical records, intraoperative recordings of auditory evoked potentials, records of postoperative auditory examinations, and imaging studies. In a series of 421 patients harboring CPA meningiomas, 72 patients in whom there was dural involvement of the IAC were investigated. Total tumor resection was achieved in 86.1%. In 34 patients, opening of the IAC was required for total tumor removal; this procedure did not influence the patient functional outcome. Among patients with secondary involvement of the IAC, anatomical preservation of the facial and cochlear nerves was obtained in 94%, whereas among patients in whom the lesion arose from the dura in or at the IAC these values were 80 and 75%, respectively. Functional preservation of the seventh and eighth cranial nerves in cases of tumor extension within the IAC was 86 and 77%, respectively, whereas in cases in which the IAC was involved it was only 60%. In four of five patients in whom the tumor had its origin in the dura mater within the IAC, the seventh or eighth cranial nerve had to be sacrificed to achieve tumor removal because of the lesion's infiltrative behavior. Facial nerve reconstruction by sural grafting was performed in the same operative procedure. Conclusions. Meningiomas of the CPA involving the IAC require special surgical management. Dural involvement of the IAC requires opening by using a diamond drill, a procedure that does not influence cranial nerve outcome. The increased rate of cranial nerve morbidity is attributed to the infiltrative behavior of these meningiomas. If affected nerve segments have to be sacrificed, immediate reconstruction enables satisfactory long-term results.