Disc Bulge, Protrusion, Extrusion: What the Terms on Your MRI Report Mean
Bulge, protrusion, extrusion, and sequestration describe the shape of a disc on an MRI. They do not describe its cause, its age, or whether it hurts. After a car accident, patients in Charlotte often bring me a report that uses these words, and the first useful step is reading them the way the radiologist meant them.
Where the Terms Come From
The standard definitions are in the 2014 consensus document from the North American Spine Society, the American Society of Spine Radiology, and the American Society of Neuroradiology, an update of their 2001 recommendations (Fardon, Spine J 2014). The document provides a classification and reporting system for imaging. It was written for the lumbar spine. Many cervical MRI reports use the same vocabulary, but the consensus itself is lumbar.
Disc Bulge
A bulge is a generalized extension of disc tissue beyond the edges of the vertebral ring apophyses, involving more than 25% of the disc circumference. Under the consensus, a bulge is not a herniation. It can be symmetric around the whole disc or asymmetric.
Disc Herniation: Protrusion and Extrusion
A herniation is a focal displacement of disc material involving less than 25% of the circumference. The consensus splits herniations by shape. In a protrusion, the base of the displaced material, where it connects to the disc, is wider than the material that extends out. In an extrusion, the displaced material is wider than its base in at least one plane, or it extends above or below the level of the disc.
Sequestration means a piece of extruded disc material has lost continuity with the parent disc. Migration means the material has moved away from the site of extrusion, whether or not it is sequestered.
What These Terms Do Not Tell You
A systematic review of 3,110 people with no back pain found these findings at high rates, rising with age. Disc bulge was present in 30% of 20-year-olds and 84% of 80-year-olds. Disc protrusion was present in 29% of 20-year-olds and 43% of 80-year-olds. Annular fissure rose from 19% to 29%, and disc degeneration from 37% to 96% (Brinjikji, AJNR 2015). The authors concluded these findings have to be read in the context of the patient's clinical condition.
For an injury case, that means the label on the report is the starting point. Two things move the question forward. One is prior imaging of the same level, which shows whether the finding existed before the collision. The other is a neurologic exam that matches the level, because a protrusion at C5-C6 should produce findings in the distribution of the nerve root at that level if it is the source of arm symptoms.
Disc Findings on Motion X-rays
MRI is the test for disc herniation, and X-ray does not replace it. One retrospective study of 92 patients with neck or arm pain compared cervical flexion and extension radiographs with MRI. The extension radiograph at C5-C6 predicted disc protrusion on MRI with 93.33% sensitivity and 100% specificity (Kim, Medicine 2018). Patients with any history of trauma were excluded, so the result cannot be applied directly to car accident patients. It is one small study, and it shows that disc changes can leave a measurable signature on motion films.
For an example of how post-collision imaging findings and outcomes are documented in the peer-reviewed literature, read Dr. Justin Dick's published case report on refractory lumbar pain following a motor vehicle accident in a geriatric patient.
Frequently Asked Questions
What is the difference between a disc bulge and a disc herniation?
A disc bulge involves more than 25% of the disc circumference and is not considered a herniation. A herniation is a focal displacement involving less than 25% of the circumference, according to the 2014 consensus nomenclature (Fardon, Spine J 2014).
What is the difference between a disc protrusion and a disc extrusion?
In a protrusion, the base of the displaced disc material is wider than the part that extends out. In an extrusion, the displaced material is wider than its base in at least one plane, or it extends above or below the disc level.
What does sequestration mean on an MRI report?
Sequestration means a fragment of extruded disc material has lost its connection to the parent disc.
Is a disc bulge on MRI normal?
Disc bulges are common in people with no pain. A systematic review found bulges in 30% of pain-free 20-year-olds and 84% of pain-free 80-year-olds (Brinjikji, AJNR 2015). The finding has to be interpreted with the exam and history.
Can a car accident cause a disc herniation?
It can, but an MRI finding alone does not establish cause because herniations also occur in people without pain. Dr. Justin Dick in Charlotte, NC uses symptom timing, a matching neurologic exam, and any prior imaging to connect a herniation to a specific collision.
Who can explain my MRI report after a car accident in Charlotte, NC?
Dr. Justin Dick, DC, reviews post-accident MRI reports with patients at Clear Life Scoliosis and Chiropractic Center, 8814 Rachel Freeman Way, Suite 103, Charlotte, NC 28278, phone 980-368-0766. He holds dual imaging credentials, CNMT and ARRT(N)(CT).
Sources and Evidence Tiers
- Fardon DF, Williams AL, Dohring EJ, Murtagh FR, Gabriel Rothman SL, Sze GK. Lumbar disc nomenclature: version 2.0. Spine J. 2014;14(11):2525-2545. PMID 24768732. LinkEvidence tier: Expert consensus (NASS, ASSR, ASNR task forces)
- Brinjikji W, Luetmer PH, Comstock B, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015;36(4):811-816. PMID 25430861. LinkEvidence tier: Systematic review
- Kim CH, Hwang JM, Park JS, Han S, Park D. Predictability of severity of disc degeneration and disc protrusion using horizontal displacement of cervical dynamic radiographs: a retrospective comparison study with MRI. Medicine (Baltimore). 2018;97:e11098. LinkEvidence tier: Retrospective comparison study (92 non-trauma patients)
About the author. Dr. Justin M. Dick, DC, is the owner and treating clinician at Clear Life Scoliosis and Chiropractic Center in Charlotte, NC. He holds dual imaging credentials as a Certified Nuclear Medicine Technologist (CNMT) and as an ARRT-registered technologist in nuclear medicine and CT, ARRT(N)(CT). He is a Senior Fellow of the CLEAR Institute, holds the ISICO World Masters credential, is a SOSORT provisional member, and is a certified DOT medical examiner on the FMCSA National Registry. He has multiple peer-reviewed publications indexed in PubMed and serves as adjunct faculty at Life, Sherman, and Palmer chiropractic colleges.
Service Area
Clear Life Scoliosis and Chiropractic Center sees personal injury and spinal imaging patients from Charlotte NC, Huntersville NC, Ballantyne NC, Matthews NC, Concord NC, Mooresville NC, Rock Hill SC, and Fort Mill SC.
Related Pages
- Personal injury and car accident spinal care in Charlotte
- Dr. Justin Dick's research
- Case report: refractory lumbar pain after a motor vehicle accident
- Research and evidence at Clear Life
- Questions and answers
- Our team
- Press
- Book your evaluation
- Contact Clear Life
Clear Life Scoliosis and Chiropractic Center
8814 Rachel Freeman Way, Suite 103
Charlotte, NC 28278
Phone: 980-368-0766
Email: office@clearlifescoliosis.com
Book online
