Prominent meningeal enhancement adjacent to meningioma on Gd-DTPA-enhanced MR images: histopathologic correlation

To assess tissue changes responsible for enhancement of the meninges adjacent to meningiomas on magnetic resonance (MR) images, the authors correlated the MR imaging characteristics of meningeal lesions seen before and after administration of gadolinium diethylenetriamine-pentaacetic acid (DTPA) with the appearance of these lesions on contrast material-enhanced computed tomographic (CT) images and with histopathologic findings in four patients. Histopathologic examination of meninges showed increased loose connective tissue, hypervascularity, and dilated vessels. There was neoplastic infiltration of the dura mater in two patients but it was restricted to the immediate junction of neoplasm and dura mater, with maximum peripheral extension within 1 mm of the tumor margin. In both patients the meninges were enhanced far beyond the neoplastic infiltration. The other two patients showed no infiltration of dura mater. These findings suggest that pathologic enhancement of meninges adjacent to meningioma after administration of Gd-DTPA mainly represents reactive changes to the neoplasm and does not necessarily indicate neoplastic involvement.