Dorsal Lumbar Disc Migrations with Lateral and Ventral Epidural Extension on Axial MRI: A Case Series and Review of the Literature.

Dorsal epidural migration of lumbar disc extrusion is rare and commonly misdiagnosed. Our purpose was to retrospectively analyze soft-tissue abnormalities on axial MR imaging in both the ventral and lateral epidural space in such dorsal epidural migrations. The presence of each component required complete concordance by 3 independent neuroradiologist readers. In a case series (n = 6) of surgically proved dorsal lumbar disc migrations, in which the radiologist's favored prospective diagnosis had not been correct, each case demonstrated epidural soft-tissue abnormality that had components both laterally and ventrally, abutting the parent disc. Similarly, in previously published cases for which axial MR imaging was available, the lateral component was demonstrated in 23/24 cases (96%). Ventral abutment of the parent disc was evident, in addition, in 17/18 cases (94%) with available disc-level axial images. Both ventral and lateral epidural soft-tissue abnormalities are typically present in dorsal lumbar disc herniations and may help radiologists suggest this rare diagnosis in appropriate cases.