In order to provide a detailed description of the MR appearance of intracranial ependymoma, the MR examinations of 12 patients (10 with ependymomas and two with subependymomas) were reviewed and correlated with operative and pathologic reports. Three of 10 ependymomas were intraventricular, two were intraparenchymal, and five were transependymal, extending from CSF spaces into parenchyma. Both subependymomas were intraventricular. Solid ependymomas and subependymomas were iso-to hypointense relative to normal white matter on T1-weighted images and hyperintense on proton-density-and T2-weighted images. Foci of signal heterogeneity within solid neoplasms represented methemoglobin, hemosiderin, necrosis, calcification, and encased native vessels or tumor vascularity. Gd-DTPA-enhanced images in two patients differentiated enhancing tumor from surrounding nonenhancing edema and from surrounding normal brain parenchyma. Cystic neoplasms had sharply defined, round or oval margins and uniform signal intensity equivalent to or slightly hyperintense relative to CSF. Tumor-associated calcification was not demonstrated readily by MR. Sagittal and coronal images were valuable in assessing the amount of intraventricular tumor and route of extension.We conclude that the MR differentiation of ependymomas and subependymomas from other gliomas is provided most reliably by the location and morphology of the tumor and not by differences in signal intensity. The typical ependymoma arises within the fourth ventricle as a solid mass with heterogeneous signal intensity. A propensity for spread is seen along the CSF pathways via the foramina of Magendie and Luschka and the aqueduct of Sylvius. Supratentorial ependymomas may be periventricular in location and have cystic components. The two subependymomas in our series were solid, intraventricular tumors with relatively homogeneous signal intensities.AJNR 11:83-91 , January/February 1990; AJR 154: April1990The appearance of intracranial ependymoma and subependymoma, although well characterized on CT [1-3] , ha? not been described in detail on MR . To our knowledge, the MR findings of ependymoma have been reported in only a few cases, as part of larger series of intracranial neoplasms [4][5][6][7][8] ; there is only one prior report on the MR manifestations of subependymoma [9].We correlated the MR findings with operative and pathologic reports in 10 patients with proved intracranial ependymomas and two patients with subependymomas. The appearance of ependymoma at low (0.35 T) and high (1.5 T) field strengths is described. Materials and MethodsWe reviewed 14 MR studies of 1 0 patients with intracranial ependymomas and two patients with subependymomas. The operative and pathologic reports and hospital and outpatient records were available for all but two patients ; these clinical data were correlated with the MR findings . The patients ranged in age from 1.2 to 59 .0 years (mean, 23.6 years). There were six females and six males. MR examinations performed at initial presentation were

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