Meningiomas of the posterior petrous bone: functional outcome after microsurgery.

Object: The aim of this study was to analyze a subgroup of patients harboring cerebellopontine angle meningiomas originating from the posterior petrous bone in regard to clinical presentation, surgical anatomy, complications, and long-term functional postoperative results.

Methods: Data in a series of 51 patients with meningiomas of the posterior petrous bone who had undergone microsurgical treatment at the authors' institution between 1989 and 2002 were retrospectively reviewed. The patient population consisted of 46 women and five men with a mean age of 53 years (range 22-70 years). The main symptom on first admission was impaired hearing in 41%, dizziness in 20%, and tinnitus in 18% of the patients. Results of physical examination and audiological testing revealed hypacusis in 65% of patients, cerebellar ataxia in 31%, and impairment of the fifth cranial nerve in 26%. All patients underwent surgical treatment via a lateral suboccipital approach. Intraoperatively, the tumor was found to be attached to the postmeatal dura in 37%, the premeatal dura in 27.5%, the suprameatal dura in 19.6%, the inframeatal dura in 7.8%, and centered on the porus acusticus in 5.9% of cases. Tumor extension into the internal acoustic meatus was present in seven patients. Tumor resection was categorized as Grade I in 14 patients, Grade II in 29, Grade III in six, and Grade IV in two patients, according to the Simpson classification system. The site of displacement of the cranial nerves was predictable in up to 84% of patients, depending on the dural origin of the tumor as depicted on preoperative magnetic resonance (MR) imaging studies. Postoperatively, a new and permanent facial paresis was observed in five patients (9.8%). In 38 patients in whom both pre- and postoperative audiological data were available, hearing function deteriorated after surgery in 18.4% and improved in 7.9%. Clinical and MR imaging postsurgical data from a mean period of 5.8 years (range 13 months-13 years) were available in all patients. Forty-four patients (86%) resumed normal daily activity. Tumor recurrence was observed in two patients (3.9%), and both underwent a second surgery.

Conclusions: Preoperative detailed analysis of MR imaging data gives the surgeon a clue about the dislocation of critical neurovascular structures, particularly the cranial nerves. Nonetheless, the exact relationship of the cranial nerves to the tumor (dislocation, adherence, infiltration, and splaying of nerves) can only be fully appreciated during surgery.