Hyperostosis associated with meningioma of the cranial base: secondary changes or tumor invasion

Hyperostosis associated with intracranial meningiomas is a well-described entity. The cause, management, and prognosis of these bony changes have long been a point of controversy. Some authors have postulated that hyperostotic changes are secondary to the formation of the tumor and do not constitute invasion of the tumor into the bone. Determining this point has direct implications in the treatment of these patients, especially regarding surgical considerations. To more thoroughly evaluate this question, a study correlating the morphology to the radiology is necessary. In this study, 51 patients underwent resection for meningiomas involving the cranial base. Preoperative radiographic evaluation using magnetic resonance imaging and/or computed tomography was performed, and areas of hyperostosis were identified. During the resection of the tumor, biopsies from these hyperostotic regions were sent for histological evaluation regarding the presence or absence of tumor invasion of the bone. Preoperative neuroradiological assessment identified 26 patients with radiographic evidence of hyperostosis. Histological examination of the resected bone showed tumor invasion in 35 patients, including the area of radiographically identified hyperostosis in 25 of the 26 patients. The floor of the middle fossa was a specific area of low sensitivity for preoperative assessment of associated hyperostosis. These results indicate that hyperostosis associated with meningiomas involving the cranial base are caused by tumor invasion of the bone histologically.