Meningeal enhancement surrounding meningiomas on Gd-DTPA MRI.

Meningeal enhancement (ME) using Gd-DTPA MRI was studied in 25 of 35 patients with meningiomas, and its clinical importance on associated MRI and histologic findings of ME was evaluated. ME extended 0.5-4.3 cm (mean: 1.5 cm) from the tumor attachment site, and was classified morphologically into two patterns: that extending with a gentle curve from the tumor attachment site to the dura, and that extending linearly. Tumor parenchyma was differentiated from ME based on time-dependent changes in signal intensity on Gd-DTPA MRI. Histologic examination was performed in tissue from regions of ME of 15 patients. Tissue corresponding to regions of ME consisted of two layers: an outer dura mater layer and an inner layer of hyperplasic loose fibrous tissue with dilated capillaries. Meningeal tumor cell clusters were observed in the fibrous tissue of 4 patients. These clusters were observed at a maximum distance of 1.4 cm from the tumor attachment site. It is thought that meningeal tumor cell clusters may represent a potential cause of local recurrence. Therefore, resection of the dura at least 2 cm from the tumor attachment site may be required to prevent local recurrence.