Bone marrow edema produces characteristic alterations in signal (low on T1- and high on T2-weighted MR images), but its pattern of presentation is highly nonspecific, posing a challenge for radiologists. Edema-like bone marrow patterns generally are reflected by ill-defined increased signal changes on fluid-sensitive sequences such as short-tau inversion recovery or fat-suppressed T2-weighted.

Images demonstrate an osteoid osteoma. It is visible on CT with a characteristic nidus (arrowhead), while on MRI only an uncharacteristic bone marrow edema pattern is visible (arrow). Additional bone scintigraphy may be also used when osteoid osteoma is suspected or when a multilocalized condition (e.g., metastatic disease) is suspected. (Provided by M. Zanetti)

The presence of bone marrow edema changes may not even be clinically relevant. Signs are often adjacent to obvious degenerative disc disease, but even incidental findings should drive further investigation if they suggest underlying infection, inflammation, or fracture.

"When bone marrow edema patterns are encountered, causes like bone contusions and infections have to be ruled out with clinical information. When such conditions are absent, mechanical stress reactions (initial stages of stress fractures) and initial stages of bone marrow necrosis are most commonly considered," said Dr. Marco Zanetti of Uniklinik Balgrist in Zurich, Switzerland, at a special focus session.

Bone mineral density changes that are part of the spectrum of abnormalities associated with a suspected disease in the vertebrae should be classified by their distribution, shape, and relationship to other local or distant abnormalities, said Prof. Frederic Lecouvet of Saint-Luc University Hospital in Brussels.

Sagittal T1-weighted (A) image of thoracic spine shows acute compression fracture of vertebral body (arrow). Posterior bulging of posterior vertebral wall (arrowhead) is suggestive of malignant origin. Coronal T1-weighted image (B) of pelvis shows evident additional foci, which confirms multifocal metastatic disease (arrowheads). (Provided by F. Lecouvet)

"The major features that will be helpful for this categorization are the distribution of the signal intensity changes within the vertebrae; their extension; their association with alterations of adjacent disc, vertebral endplates, or soft tissues; and the presence of similar changes of other more suggestive abnormalities, such as tumor foci, at other levels," he said.