A disc bulge pushes past the disc’s normal edge around more than a quarter of its rim. It is broad, even on both sides, and usually comes with age. A herniation is focal (in one spot), under a quarter of the rim. It matters when it presses on the nerve root that matches your symptoms.
These are not the same thing. Reports use the words with care, even when patients and websites do not.
In more detail
- A bulge is the disc pushing past its normal edge around more than a quarter of its rim. It is broad, even on both sides, and usually comes with age. It is common in people without pain.
- A herniation is focal: under a quarter of the rim. It comes in degrees. There is a protrusion where the base is wider than the material pushing out, an extrusion where the material pushing out is wider than its base, and a sequestration where a fragment has separated entirely.
- It sounds backward, but larger extrusions and sequestrations often get reabsorbed more fully over months than small protrusions do.
What it means for you
A bulge with no matching symptoms usually does not matter. A focal herniation pressing on the nerve root that matches your symptoms is the one worth treating. Most herniations get better without surgery.
Remember the general rule. Findings like this one are common in people with no pain at all. They get steadily more common with age. A finding on a report is not a diagnosis until someone has matched it to your symptoms and your exam. See understanding your MRI report.
Bring your scan and report in and we will go through it with you. Call us or request an appointment.
How common is it, and what does it predict?
A bulge is a broad, mostly even push of the disc wall past its normal edge. It takes in more than a quarter of the rim. A herniation is focal and takes in less than that. It is split into protrusion, extrusion and sequestration. The split depends on how far the material has moved and whether it is still attached. Patients read herniation as the more serious word. On its own, it is not. What predicts symptoms is whether the material touches or inflames a nerve root, not which word the radiologist chose.
Common questions
Which is worse, a bulge or a herniation?
Neither is worse by default. A large bulge that causes no symptoms matters less than a small herniation sitting on the exact nerve causing your leg pain.
The detail is in Herniated Disc.
Can a herniated disc go back in?
The material often shrinks and is reabsorbed over months. It does not ‘pop back’, but the end result is often the same.
Is a herniation worse than a bulge?
Not reliably. Large bulges are often painless, and small herniations are sometimes not. Contact with a nerve root is what matters.
This is set out in Understanding Your MRI Report.
What is an extrusion?
It is disc material that has moved farther than a protrusion, at times past the disc space. Larger extrusions often shrink a great deal over months.
The mechanism is covered in Herniated Disc.
Will a herniation shrink on its own?
Often, yes. Larger extrusions in particular often shrink a great deal over months. That is one reason time and symptom control are tried before surgery.
How and why herniations shrink is covered in Herniated Disc.
Sources
- Fardon DF et al. 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. The spine journal : official journal of the North American Spine Society, 2014. PubMed 24768732
- Williams AL et al. Lumbar disc nomenclature: version 2.0. AJNR. American journal of neuroradiology, 2014. PubMed 25339648
- Zhang AS et al. Lumbar Disc Herniation: Diagnosis and Management. The American journal of medicine, 2023. PubMed 37072094
- Brinjikji W et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR. American journal of neuroradiology, 2015. PubMed 25430861
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