MR imaging of epidural hematoma in the lumbar spine.

Abstract

To bring attention to the MR imaging appearance of epidural hematoma (EDH) in the lumbar spine as a small mass often associated with disk herniation or an acute event. This paper will show our experience with this entity and describe criteria for its MR imaging appearance. Thirteen cases of prospectively diagnosed EDH of the lumbar spine were compared with 12 cases of prospectively diagnosed prominent epidural extrusion. Our criteria were retrospectively evaluated by the two authors for their presence or absence in each case. The chi-square test for nominal data was applied. MR imaging criteria utilized to distinguish EDH from disk herniation at our institution include: (1) signal different from disk, (2) high signal on T1-weighted images, either centrally or peripherally, (3) teardrop- or egg-shaped mass, in the sagittal plane, (4) size greater than half the vertebral body height in a craniocaudal dimension, (5) primarily retrosomatic epidural location, (6) plasticity - the mass is seen to conform closely to the contours of bone (e.g., in the lateral recess), (7) little or no disk space narrowing unless associated with disc herniation. Chi-square analysis demonstrated each criterion to significantly differentiate between EDH and extrusion. Only six of 13 EDH cases went to surgery in spite of their relatively large size. Two of six patients were diagnosed as having epidural clot consistent with hematoma at the time of surgery. The four patients who were not diagnosed at surgery revealed only small disk herniations or fragments of disk. The occurrence of EDH is more frequent than previously suspected. Spontaneous EDH is frequently associated with disk herniation and acute events such as sneezing or coughing. Most cases of spontaneous EDH will resolve prior to surgery with only the minority becoming chronic in order to be seen at surgery as an encapsulated mass. MR imaging can reliably identify EDH and distinguish between EDH and large disk extrusions.