MR characteristics of histopathologic subtypes of spinal ependymoma.

PURPOSE To examine MR characteristics and enhancement patterns of spinal ependymomas and compare these data with histopathologic subtypes.

METHODS The MR images from 26 cases of pathologically proved spinal ependymomas were evaluated with respect to seven criteria: signal characteristics, enhancement pattern, length of involvement, cysts or syrinxes, hemorrhage, bony changes, and type of cord expansion. Signal characteristics were then correlated with histologic subtype.

RESULTS In the category of enhancement pattern, our results differed markedly from published data, with only 38% of cases demonstrating classic homogeneous enhancement. The remainder of our cases (62%) demonstrated other enhancement patterns, including heterogeneous (31%), rim (19%), minimal (6%), and no enhancement (6%). Pathologic comparison revealed that one histologic subtype, the myxopapillary ependymoma, demonstrated unique imaging characteristics on T1-weighted images. A highly statistically significant percentage of this variant was hyperintense on T1, whereas most nonmyxopapillary ependymomas were hypointense.

CONCLUSION The radiologist should be aware of alternative patterns of enhancement of spinal ependymomas and not be dissuaded from the diagnosis in appropriate clinical settings. In addition, one histologic subtype, myxopapillary, often exhibits signal characteristics different from nonmyxopapillary types, appearing hyperintense on T1 probably because of their intracellular and perivascular accumulation of mucin.