Peritumoral blood flow in intracranial meningiomas. Blood flow was measured in intratumoral tissue, the cerebral hemispheres and particularly in the peritumoral area of 12 patients with intracranial meningiomas using the stable xenon-enhanced computed tomographic scan. Tumor blood flow frequently showed a heterogeneous pattern of enhancement with high flow at the tumor periphery and a central area of hypoperfusion. Blood flow values were on average 28% lower in the peritumoral area than in the ipsilateral cerebral hemisphere. In individual cases, blood flow values in the peritumoral edematous area were very low. These findings suggest that the hypodense area surrounding meningiomas does not solely represent vasogenic edema, but may actually represent tumor pressure ischemia. 