Cerebral edema in intracranial meningiomas: evidence for local and diffuse patterns and factors associated with its occurrence.

In a review of 68 meningiomas with good quality computed tomography (CT) scans, 40% had significant CT edema, in the sense of having low absorption around tumor. Two distinct patterns of edema could be distinguished. One was a diffuse white matter process appearing to represent active transudation of water into white matter; this occurred in 43% of tumors with edema. The second, occurring in 57% of tumors with edema, was a localized peritumoral process. This distinction has important pathophysiologic and clinical implications. The diffuse pattern did not appear to reflect tumor size: it was found in 54.6% of tumors from 2 to 4 cm in diameter and 33% of tumors over 4 cm. It appeared more often in tumors of the lateral sphenoid wing or subfrontal region and was more often associated with atypical and syncytial histological type, (p < 0.05, two-tailed t test.). It occurred disproportionately often in atypical tumors and appeared to reflect some intrinsic property of the tumor rather than compression of surrounding structures.