Case 25
History:
64 year old female with right lower extremity pain and back pain
Findings:
L spine MRI showing a soft tissue lesion in the right epidural space just inferior to the L5-S1 space resulting in mass effect upon the traversing right S1.
Diagnosis:
Migrated disc
Discussion:
The recommendations of the Combined Task Forces of the North American Spine Society, American Society of Spine Radiology, and American Society of Neuroradiology published in 2001:
“Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material.
Protrusion is present if the greatest distance, in any plane, between the edges of the disc material beyond the disc space is less than the distance between the edges of the base in the same plane. The base is defined as the cross-sectional area of disc material at the outer margin of the disc space of origin, where disc material displaced beyond the disc space is continuous with disc material within the disc space. In the cranio-caudal direction the length of the base cannot exceed, by definition, the height of the intervertebral space.
Extrusion is present when, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base in the same plane, or when no continuity exists between the disc material beyond the disc space and that within the disc space. Extrusion may be further specified as sequestration, if the displaced disc material has lost completely any continuity with the parent disc.
The term migration may be used to signify displacement of disc material away from the site of extrusion, regardless of whether sequestrated or not. Because posteriorly displaced disc material is often constrained by the posterior longitudinal ligament, images may portray a disc displacement as a protrusion on axial sections and an extrusion on sagittal sections, in which cases the displacement should be considered an extrusion. Herniated discs in the cranio-caudal (vertical) direction through a break in the vertebral body end-plate are referred to as intravertebral herniations.
Disc herniations may be further specifically described as contained if the displaced portion is covered by outer anulus, or uncontained when absent any such covering. Displaced disc tissues may also be described by location, volume, and content.
