Specific Imaging Findings

On CT, ependymomas are usually iso- to hypodense compared with normal brain. Approximately 50% contain internal calcifications and hemorrhage can also be seen in approximately 10% of tumors. The tumor is heterogenous, T1 iso- to hypointense, and hyperintense on T2-weighted imaging. T1 hyperintense and T2 hypointense areas may be found, representing calcifications and sometimes blood products. The lesions are frequently heterogenous on ADC maps, the more solid portion of the tumor is generally slightly brighter than the normal brain; anaplastic (higher grade) ependymomas may contain dark areas of very low diffusion. Following contrast, ependymomas show some degree of usually heterogenous enhancement, although non-enhancing tumors can occasionally be seen, especially with recurrent disease. Perfusion studies demonstrate markedly elevated cerebral blood volume (but, unlike other glial neoplasms, poor return to baseline). Due to the propensity for leptomeningeal disease and drop metastases, imaging of the entire neural axis is required. A fourth ventricle mass that extends through the foramina of Luschka and Magendie into the cerebellopontine angle and cisterna magna is a characteristic appearance of the infra-tentorial ependymomas. Supratentorial ependymomas are commonly extraventricular, located along or near the ventricular margin within the cerebral hemispheres; they also tend to be larger and more heterogenous and are frequently anaplastic.