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A disc extrusion a type of intervertebral disc herniation and is distinguished from a disc protrusion in that it:
- has a broader dome (B) than neck (A), and / or
- extends above of below the disc level (into the suprapedicular or infrapedicular zone)
It is associated with a defect in the annulus fibrosus which allows herniation of nucleus pulposus beyond the confines of the disc.
Extrusion can be in any axial direction and may migrate either superiorly or inferiorly. If the extrusion migrates but becomes separated from the rest of the herniation it is known as a intervertebral disc sequestration.
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