MR Imaging Findings of Paget's Disease of the Spine.

Paget's disease (PD) is a common bone disorder of the aging population where the spine is the second most common involved location after the pelvis. Though imaging findings are well described on CT and radiographs, recognition on MRI can be challenging. We reviewed 16 cases with radiologic or histologic confirmation of uncomplicated PD of the spine. In most cases, MRI showed a mixed pattern of increased/ decreased T1 signal (fine trabecular or coarse) of the vertebral bodies. There was also associated band-like decreased T1 and T2 signal of the endplates. This correlates with the mixed osteolytic and blastic phase of the disease, the most common phase in the spine. Subtle or conspicuous "picture-frame" appearance may also be identified. Present in most cases, but frequently overlooked manifestation on MRI, was the expansion of the vertebral body and/or posterior elements/ spinous process. We identified a subtle diffuse decreased T1 and T2 bone marrow signal, not corresponding to sclerosis on CT or radiographs, in two cases. We proposed this, as an earliest sign on MRI, likely representing early fibro-vascular bone marrow transformation and to our knowledge not previously described. Less commonly, sclerotic PD was also found which is perhaps the most difficult to evaluate given its broad differential. Most cases of PD of the spine were overlooked or confused with other entities by the radiologists. Interpretation of MR images of the spine in the absence of prior imaging is not uncommon. Thus, recognition of MRI manifestations is important to allow appropriate management, to avoid misinterpretations and in most cases to avoid biopsy.