Spinal Epidural Space:
Anatomy, Normal variations, and Pathological Lesions
on MR Imaging

Chhabra A, MD¹; Batra K, MD¹; Satti S, MD¹; Patel S, MMS¹; Feitell S, MMS¹; Gonzales C, MD¹; Faerber E, MD²; Koenigsberg RA, DO FAOCR¹

¹Drexel University College of Medicine, Philadelphia, PA
² St Christopher Hospital for Children, Philadelphia, PA

Normal Variations and Pseudo-tumors

1. The shape of the fat changes from triangular to crescent when moving from lumbar to thoracic levels and there is paucity of fat at thoracic-cervical levels (Fig- 2a,b). At T11-12, C7-T1, L2-3 levels, no appreciable fat is seen in most subjects.
2. Epidural space becomes widely patent as the fatty tissue in the epidural space diminishes with increasing age.
3. Deep breathing expands the potential cavity of the epidural space.
4. The ligamentum flavum has increased signal intensity on T1-weighted images compared with other ligamentous structures simulating calcification because of the heavy concentration of elastin (Fig- 3). When axial forces are applied to the spine, the ligamentum flavum may appear to bulge and narrow the posterior epidural space.
5. A focal prominence of the basivertebral vein or epidural venous plexus may simulate a small disk herniation on sagittal or transaxial images (Fig- 4a,b). Because the venous plexus enhances with gadolinium, further confusion with a mass may occur. In sagittal images, lumbar veins at the periphery of the spine should not be confused with a basivertebral vein. The basivertebral veins are noted on mid sagittal images, whereas lumbar veins are at the periphery of the vertebral bodies.
6. The air resulting from vacuum phenomena from a degenerative disk or facet joint may diffuse into the epidural space and be a source of diagnostic pitfall.
7. A redundant or prominent posterior longitudinal ligament may resemble a vertebral osteophyte. This is most likely to occur on gradient echo images when the ligament is calcified.
8. The dorsal root ganglia may enhance after the administration of gadolinium.