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.