Marrow edema

Bone marrow edema is the term given to abnormal fluid signal seen within the bone marrow on MRI. It is a non-specific, yet important finding usually indicating the presence of underlying pathology.

Pathology

Etiology

There is a long (long) list of possible causes of this finding:

• primary: bone marrow edema syndrome (no cause found)
• trauma: fractures, bone contusion, ligamental injury, etc.
• arthropathy: e.g. degenerative joint disease, rheumatoid arthritis, etc.
• hypoperfusion: e.g. sickle cell disease
• infective: e.g. osteomyelitis, diskitis, septic arthritis
• iatrogenic: e.g. chemotherapy, postoperative, chronic corticosteroid therapy
• neurological: neuropathic arthropathy
• neoplastic: malignancies e.g. bone metastases, and benign e.g. giant cell tumor, chondroblastoma, osteoid osteoma
• miscellaneous: e.g. chronic renal failure

Radiographic features

CT

Dual-energy CT may demonstrate bone marrow edema using fluid-sensitive "edema maps", however its sensitivity and specificity is poorer than that of MRI .

MRI

Bone marrow edema is generally primarily identified on MRI and is best investigated using fat-suppressed T2W sequences.

There will be intermediate T1 signal, with high T2 signal in the fat of the bone marrow (usually fat-suppressed sequences required to see the increased T2 signal).

However other imaging modalities may then have a role in investigating the underlying cause.