So, you got your MRI back, and you see that you have a disc bulge. What now? This week the post trending on the back pain subreddit was about MRI findings in people with no back pain. That caught my eye because spinal health was one of my areas for my PhD comprehensive exams, and one of the studies I had to look at was about exactly this.
TLDR
- About 30% of pain-free 20-year-olds have a disc bulge on MRI. By age 80 it's 84%.
- Bulges are more common in people with back pain, so they're not meaningless. They just may not be the cause.
- The scariest-sounding herniations shrink on their own more often. Bulges mostly stay put.
- How your MRI is explained to you may affect how you recover.
Bulges and the jelly-filled onion
My PhD supervisor described the intervertebral disc, the cushion between our spinal bones, as a jelly-filled onion. The nucleus pulposus is the centre jelly; the annulus fibrosus is the outer wrap of collagen layers.
A disc bulge is when the disc's outer rings extend a little past the edge of the vertebra, broadly and evenly. The jelly hasn't left the disc. [1]
Extrusion and sequestration mean the jelly has pushed out through the onion. Herniation is the umbrella word, and it includes protrusions, where the jelly pushes into the layers but stays inside. [1]
What shows up in pain-free backs
A 2015 review examined MRI and CT scans of over 3,000 pain-free people. Bulges went from 30% at age 20 to 84% at age 80. Many changes, including disc degeneration (age-related disc changes), were considered normal aging and weren't necessarily causing pain. [2]
The same group compared MRIs from people with and without low back pain. [3] A disc bulge on an MRI doesn't prove it's what's causing someone's pain. So they are linked: bulges were more common in people with back pain, though the estimate was very imprecise, so the exact size of that link is uncertain. [3]
In my experience, plenty of people with painful backs get an MRI and nothing obvious shows up.
There's no perfect relationship between abnormalities and back pain. Plenty of pain-free people have bulges, herniations and disc degeneration. [2,3]
So your scan isn't meaningless, but it might not identify what's causing your pain. [2,3] In my opinion, how your back responds to movement is much more important.
Do they shrink?
Spontaneous herniation regression, where displaced disc material shrinks, was almost my PhD topic. I wrote my scholarship proposals on it before deciding to look elsewhere.
The more severe a herniation is, meaning the greater the extrusion or sequestered material, the more likely they are to shrink on their own on follow-up scans.
The body treats the jelly as something that doesn't belong there and mounts an inflammatory clean-up response that clears it, mostly within about 6 months. [4,5]
A 2024 meta-analysis examined over 30 studies of bulges and herniations and measured how often they shrank over time. [5] Thankfully, about 70% of them shrank on follow-up scans with conservative care, meaning no surgery. The bigger herniations shrank most often; plain bulges shrank far less often.
In numbers, bulges were the least likely to shrink (about 13%) and sequestrations the most likely (about 88%).
As a biomechanist, I'm looking for mechanical explanations. Jelly that has broken free comes into contact with the blood supply, and that sets off the immune response. [4] My read is that a contained bulge doesn't set off the same clean-up response, so it tends to linger.
The review measured shrinkage on scans, not pain or recovery, and rates varied a lot between studies and countries. [5]
A bulging disc mostly stays the way it is. [5] Many people live with them without problems or surgery. [2] Guidelines still recommend conservative care first. [4]
How the report gets explained
An Indian study randomly assigned 44 people with low back pain to two groups that heard different explanations of their MRIs. [6] The first group got a plain, factual explanation of what was found. The second group, regardless of their scans, was reassured that their findings were normal changes.
After six weeks, they looked at their pain, their function and how they felt about their spines.
The factual-explanation group had more catastrophizing (expecting the worst). They had more negative views, less pain improvement and worse function. How we describe MRI findings seems to affect people's perceptions and recovery. [6] This was a small study at one hospital, with six weeks of follow-up.
What to do this week
- Keep moving. Find movements that don't hurt your back and continue doing them to the best of your ability. Always maintain walking. In my opinion, walking is one of the best ways to stay active without aggravating your back.
- Ask whoever ordered your scan to explain it alongside your symptoms. They may or may not match. [2]
- Don't avoid movement because of words on a page. If you're able to move and continue to live your life, then you should keep doing so.
If you notice new leg weakness, numbness in your groin or inner thighs, or changes in bladder or bowel control, contact a doctor right away. New pain down your leg is worth booking an appointment for.
As always, have a great weekend.
Best,
Mitch
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References
[1] Fardon et al., 2014. 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. doi:10.1016/j.spinee.2014.04.022
[2] Brinjikji et al., 2015. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR. doi:10.3174/ajnr.A4173
[3] Brinjikji et al., 2015. MRI Findings of Disc Degeneration are More Prevalent in Adults with Low Back Pain than in Asymptomatic Controls. AJNR. doi:10.3174/ajnr.A4498
[4] Xie et al., 2024. Prevalence, clinical predictors, and mechanisms of resorption in lumbar disc herniation: a systematic review. Orthopedic Reviews. doi:10.52965/001c.121399
[5] Zou et al., 2024. Incidence of Spontaneous Resorption of Lumbar Disc Herniation: A Meta-analysis. Clinical Spine Surgery. doi:10.1097/BSD.0000000000001490
[6] Rajasekaran et al., 2021. The catastrophization effects of an MRI report on the patient and surgeon and the benefits of 'clinical reporting': results from an RCT and blinded trials. European Spine Journal. doi:10.1007/s00586-021-06809-0
Disclaimer: this content is educational only and does not constitute medical advice. See a practitioner if you suspect serious spinal trauma from a fall or accident, or if you experience any of the following red flag symptoms: loss of bowel or bladder control, numbness in the groin or saddle area, rapidly worsening leg weakness, back pain with fever or feeling generally unwell, or unexplained weight loss with back pain.