Petrous Bone Meningiomas

Petrous bone meningiomas do not represent, from the surgical point of view, a homogeneous group of tumors. We have identified four groups of tumors according to the different areas of origin on the posterior surface of the petrous bone. The aim of this study is to evaluate the prognosis in relation to tumor location and cranial nerve involvement. In the last 15 years we have operated on 55 patients having petrous bone meningioma: 44 females, 11 males, from 16 to 75 years of age. In 16 patients the origin of the tumor was posterior to the internal auditory canal (IAC) (Group A). In 24 cases the origin was adjacent to the IAC (Group B): between the IAC and the jugular foramen (B1) or between the IAC and the tentorium (B2). In 10 cases the tumor was of small size anterior to the IAC, corresponding to the petros apex (Group C); in 5 cases the origin was broad-based on the posterior surface of the petrous bone (Group D). All patients were operated on using a retrosigmoid approach.

In Group A the surgical results were generally good with no significant postoperative deficits except in 1 case in which there was a postoperative hematoma.

In Groups B and C the surgical results were less favorable due to various deficits of the cranial nerves (mainly VII, VIII, V, and IX) and only partial removal of the tumor (2 cases).

In Group D there was 1 death, 1 partial resection, and 2 patients had postoperative cranial deficit.

The difficulty involved in the surgical removal of petrous bone meningiomas, and consequently in the surgical results, depends upon the site of origin of these tumors owing to cranial nerve and vessel involvement.