A disc extrusion is defined by the herniated part of the disc being larger compared to the base of the herniation. The part of the disc that is pushed out past the disc space is larger compared to where it herniated. The disc extrusion can be further classified if the herniated disc material is no longer attached to the disc itself. This type of herniated disc is called a sequestered disc.
A disc extrusion is shown below.
References
Fardon DF, Williams AL, Dohring EJ, Murtagh FR, Gabriel Rothman SL, Sze GK. Lumbar disc nomenclature: version 2.0: Recommendations of the combined task forces of the North American Spine Society, the American Society of Spine Radiology and the American Society of Neuroradiology. Spine J. 2014 Nov 1;14(11):2525-45. doi: 10.1016/j.spinee.2014.04.022. Epub 2014 Apr 24. Review. PubMed PMID: 24768732.
