A bulging disc involves the outer part of the disc (annulus fibrosus) bulging outward, past the disc space. The annulus fibrosus is intact, the nucleus pulposus (inner part of the disc) is not pushed out through the annulus, as occurs with a herniated disc.
A bulging disc can be symmetric or asymmetric. A symmetric bulging disc involves annular tissue that extends beyond the vertebral apophyses symmetrically throughout the circumference of the disc. An asymmetric bulging disc is defined as annular tissue that extends beyond the edges of the vertebral apophysis, asymmetrically greater than 25% of the circumference of the disc.
Upper left: Normal disc. Upper right: Symmetrical bulging disc. Bottom center: Asymmetric bulging disc
Bulging discs are common and should be viewed as normal, as the majority of people without lower back pain have bulging discs.
In asymptomatic people, without lower back pain 30% of 20-year-olds have at least one bulging disc. 84% of 80-year-olds have at least one bulging disc. As humans age bulging discs become more and more prevalent. In people WITHOU lower back pain.
A bulging disc can be painful. It’s important to correlate imaging findings with the clinical presentation. It’s also important to know that having a bulging disc does not mean you have a bad back or are injured. It means you spine and discs are like the majority of other people, who do not have lower back pain.
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.
Brinjikji W, Luetmer PH, Comstock B, Bresnahan BW, Chen LE, Deyo RA, Halabi S, Turner JA, Avins AL, James K, Wald JT, Kallmes DF, Jarvik JG. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015 Apr;36(4):811-6. doi: 10.3174/ajnr.A4173. Epub 2014 Nov 27. Review. PubMed PMID: 25430861; PubMed Central PMCID: PMC4464797.
