"Meningeal sign": a characteristic finding of meningiomas on contrast-enhanced MR images.

In meningiomas, a flat, contrast-enhancing, probably dural structure adjacent to the tumor can occasionally be observed on Gadolinium-DTPA enhanced MR images. This so called "meningeal sign" was evaluated with respect to the differential diagnosis of meningiomas in MR imaging. The study included 29 patients with intracranial meningiomas and 24 patients with non-meningeal brain tumors. In all meningiomas, MR studies included T2-weighted as well as unenhanced and Gadolinium-DTPA-enhanced T1-weighted images. In all non-meningeal tumors, Gd-DTPA-enhanced MR images were available. All images were evaluated with respect to the presence of the "meningeal sign". In meningiomas, a "meningeal sign" was seen in 15/29 cases on Gadolinium-DTPA-enhanced images. No abnormalities corresponding to the areas of contrast enhancement were found on unenhanced T2- and T1-weighted MR images. In non-meningeal tumors only 2/24 cases showed a "meningeal sign". In conclusion, with a sensitivity of 52% and a specificity of 92%, the demonstration of the "meningeal sign" improved the differential diagnosis of intracranial meningiomas in contrast-enhanced MR imaging.