Abstract：Objective: To summarize the MR imaging features of atypical meningiomas. Materials and Methods: There were 11 cases with atypical meningiomas proved by pathology, both plain and post-contrast MRI were performed in all the cases. Four cases had diffusion weighted imaging(DWI). The MRI manifestations including location, size, shape and margin of tumors, the signal intensity of lesions, the peritumor edema, dural tail sign, blood vessel flow void sign and signal intensity of DWI were analyzed. Results: Most of the lesions located in the cerebral convexity with average diameter larger than 5cm, and showed inhomogeneous signal intensity before and after contrast administration with irregular shape and blurred margin. In the lesion there were multiple flow void blood vessels and on DWI the tumor showed high and slightly high signal intensity. Two cases had invasion of sinus sagittalis superior, adjacent skull and soft tissue respectively. Peritumor edema and dural tail sign are not specific signs in the diagnosis of atypical meningiomas. Conclusion: When a tumor located in the common sites of meningioma with a larger size and atypical features including irregular shape, blurred margin between cerebral parenchyma and tumor, inhomogeneous signal intensity before and after contrast administration, blood vessel flow void sign in tumor and/or invasion of adjacent tissue, the diagnosis of atypical meningiomas should be considered.
2009, Vol. 20 
