Paraseller meningiomas: incidence of involvement of extracavernous structures as determined by magnetic resonance and computed tomography.

Parasellar meningiomas frequently extend beyond the cavernous sinus into adjacent structures. In order to determine the incidence of involvement of adjacent sites, we retrospectively evaluated the computed tomography and nuclear magnetic resonance scans of 65 consecutive patients with meningiomas invading the cavernous sinus. Thirteen nearby anatomic sites were analyzed for tumor involvement. The sites most frequently involved were the lateral sphenoid sinus wall (93%), the ipsilateral petrous apex (70%), the ipsilateral posterior petrous bone surface (59%), the sella (59%), the intracranial clival surface (44%), and the suprasellar cistern (41%). The sella, clival bone marrow, orbital apex, pterygopalatine fossa, and prestyloid parapharyngeal space were more commonly involved in recurrent tumors. Lesions were also subdivided into five groups according to whether or not they involved only one part of the cavernous sinus (grade 1), two parts of the cavernous sinus (grade 2), surrounded the cavernous carotid artery (grade 3), surrounded and narrowed the cavernous carotid artery (grade 4), or involved both sides of the cavernous sinus (grade 5). Among the 63 cases that could be assigned to a category, seven were grade 1 lesions, 13 were grade 2, 13 were grade 3, 16 were grade 4, and 14 were grade 5. Tumor grade is helpful in predicting the difficulty of resection of the cavernous component of the tumor. The incidence of involvement of adjacent sites is also helpful in assessment of imaging studies and in planning the most appropriate surgical approach.