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 imaging 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, ligamentous 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 5.
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.