Most intracranial meningiomas are not cleavable tumors: anatomic-surgical evidence and angiographic predictibility.

Objective: The statement that intracranial meningiomas are cleavable tumors has to be seriously questioned from a surgical standpoint. The purpose of this study was 1) to analyze the operative reports of a personal series of meningiomas to evaluate the percentages of the tumors that could be dissected by passing in the extrapial plane (i.e., "cleavable") and of those in which the dissection had to be subpial (i.e., "noncleavable") and 2) to see whether preoperative angiography could help in predicting cleavability.
Methods: The series includes 150 consecutive patients with intracranial meningiomas diagnosed with computed tomographic scans and explored preoperatively by selective external/internal carotid angiography, operated on using microsurgical techniques, and followed for more than 4 years.
Results: Dissection between tumor and underlying cortex could be achieved in the extrapial plane predominantly (i.e., on more than two-thirds of the interface) in only 54.6% of patients. On angiography, the pial-cortical arterial supply participated in at least equal part with the meningeal-dural arterial supply in vascularization of the tumor in 59.4% of patients. In this group, dissection could pass through the extrapial plane in only 34.8% of patients. Conversely, when meningeal-dural arterial supply was predominant on angiography, which occurred in 40.6% of patients, dissection could be achieved in the extrapial plane in 83.6% of patients. This difference is statistically significant (P < 0.001).
Conclusion: Participation of pia mater in the vascular supply of intracranial meningiomas, and consequently, difficulty of dissection, can be predicted preoperatively on angiography. Knowledge of the arterial supply of the tumor before surgery is an important aid to the surgeon in preparing for and performing the operation.