Contrast-enhanced MR images in patients with meningioma: importance of enhancement of the dura adjacent to the tumor

Linear enhancement (flare sign) along the dura mater that was continuous with or emanated from the dural margin of meningiomas was frequently observed on contrast-enhanced MR images obtained in 18 patients with intracranial meningiomas (surgically proved). Preoperative MR studies obtained at 1.5 T after administration of gadopentetate dimeglumine were reviewed retrospectively to determine the clinical significance of this sign. Thirteen (72%) of the 18 meningiomas exhibited the finding adjacent to the dural attachments. Four meningiomas of the cerebellopontine angle showed enhancement along the internal auditory canals. Three specimens of the dura adjacent to the tumor in different patients with this finding revealed proliferation of connective tissues abounding with vessels along the dura without definite tumor invasion. The flare sign is thought to be a common finding of meningiomas on contrast-enhanced MR images obtained with high-resolution sequences, and it is observable without tumor invasion. This sign in the cerebellopontine angle should not be misinterpreted as enhancement of acoustic schwannomas.