MR CHARACTERISTICS OF HISTOPATHOLOGIC SUBTYPES OF SPINAL EPENDYMOMA

PURPOSE: To examine MR characteristics and enhancement patterns of spi nal ependymomas and compare these data with histopathologic subtypes. METHODS: The MR images from 26 cases of pathologically proved spinal e pendymomas were evaluated with respect to seven criteria: signal chara cteristics, enhancement pattern, length of involvement, cysts or syrin xes, hemorrhage, bony changes, and type of cord expansion. Signal char acteristics were then correlated with histologic subtype. RESULTS: In the category of enhancement pattern, our results differed markedly fro m published data, with only 38% of cases demonstrating classic homogen eous enhancement. The remainder of our cases (62%) demonstrated other enhancement patterns, including heterogeneous (31%), rim (19%), minima l (6%), and no enhancement (6%). Pathologic comparison revealed that o ne histologic subtype, the myxopapillary ependymoma, demonstrated uniq ue imaging characteristics on TI-weighted images. A highly statistical ly significant percentage of this variant was hyperintense on T1, wher eas most nonmyxopapillary ependymomas were hypointense. CONCLUSION: Th e radiologist should be aware of alternative patterns of enhancement o f spinal ependymomas and not be dissuaded from the diagnosis in approp riate clinical settings. In addition, one histologic subtype, myxopapi llary, often exhibits signal characteristics different from nonmyxopap illary types, appearing hyperintense on T1 probably because of their i ntracellular and perivascular accumulation of mucin.