Imaging characteristics of noncontained migrating disc fragment and cyst

The purpose of this article is to review less common presentations of degen erative disc disease on MR imaging. The images of eight patients were retro spectively analyzed. Six of them had transligamentous (or noncontained) dis c herniations, the fragments of which were located in the posterior epidura l space in three of them. One patient had a transdural disc fragment and on e patient had a disc cyst. The cyst was located in the ventrolateral epidur al space. On T2-weighted images, the migrated disc fragment returned a high er signal than the disc of origin in 6 of 7 patients. The disc cyst returne d a signal similar to that of cerebrospinal fluid. The MR appearances of di sc fragments can be puzzling, particularly if they are located in the poste rior epidural space. It is important to recognize the abnormalities in orde r to differentiate them from less common lesions such as hematoma, abscess and neurinoma.