Meningiomas comprise approximately 20% of adult primary intracranial neoplasms.1 Of these, benign meningiomas are known to have an indolent growth pattern, usually without infiltration into adjacent nervous tissue.2–5 Because meningiomas have a well-circumscribed character, surgery has historically been the preferred treatment when total resection can be achieved with reasonable morbidity. Surgical resection has resulted in five-, 10-, and 15-year progression-free rates of 93, 80, and 68%, respectively.6 Despite the development of multiple techniques designed to minimize morbidity while obtaining a surgical cure, however, complete resection remains difficult and is not achievable in approximately 20–30% of presenting patients because of multiple regional involvement, severe adherence to or invasion of the brainstem, involvement of cranial nerves, or encasement of the vertebrobasilar circulation.6–11 Currently, controversy exists as to whether skull base meningiomas, especially those involving the petroclivus and/or cavernous sinus, are best treated with radical resection, subtotal resection followed by radiosurgical treatment of the residual lesion, or radiosurgical treatment alone.
Petroclival Tumors and Cavernous Extension
Meningiomas of the petroclival region usually involve the petrous apex and the upper two-thirds of the clivus.10 Most are complex and, with modest enlargement, may involve multiple regions. Clival extension is usually unilateral for those tumors involving the upper and midclival regions.10 However, additional complexity exists for those centrally located lesions with respect to the clivus that have bilateral cavernous sinus involvement and/or extradural extension into the sphenoid sinus.10
Petroclival meningiomas are among the most difficult tumors of the cranial base for which to obtain surgical cure. Therefore, treatment must take into account the natural history of the tumor, degree of extension, neurovascular involvement, and the patient’s level of disability.12,13 Despite significant improvements10,14–17 in the surgical treatment of petroclival meningiomas, tumor may be left behind because of the invasion of the cavernous sinus, encroachment or encasement of cranial nerves, involvement of cerebral arteries, or invasion of the brainstem pial membrane. On this note, the management of tumors with neurovascular involvement has changed considerably over the past few years. Appropriately, cautious subtotal resection has become the preferred treatment to reduce post-operative morbidity, along with the addition of radiation treatment of tumor remnants.18–21