MRI reports are written by radiologists for other doctors, so the words can sound frightening: degeneration, desiccation, protrusion, stenosis. This guide explains what they mean in plain language. The most important thing to know first is that a report describes what the scan shows. It does not, on its own, tell you what is causing your pain.
Many MRI findings are normal for your age
A review of 33 studies covering 3,110 people with no back pain at all found that disc changes are very common and become more common with age (Brinjikji, AJNR 2015):
| Finding in people with no back pain | At age 20 | At age 80 |
| Disc degeneration | 37% | 96% |
| Disc bulge | 30% | 84% |
| Disc protrusion | 29% | 43% |
| Annular fissure | 19% | 29% |
An earlier study scanned 98 adults without back pain: 52% had a disc bulge at one level or more, 27% had a protrusion, and only 36% had normal discs at every level (Jensen, NEJM 1994). The authors concluded that finding a bulge or protrusion in someone with back pain may often be coincidence.
This does not mean your scan is meaningless. It means the findings only matter when they match your symptoms and examination.
How to read the levels: L4/L5 and L5/S1
Your lower back has five vertebrae, L1 to L5, sitting on the sacrum (S1). Discs are named after the two bones they sit between, so L4/L5 (also written L4-L5 or L4-5) is the disc between the fourth and fifth lumbar vertebrae, and L5/S1 is the last disc, between L5 and the sacrum. These two lowest discs carry the most load and movement, and they are where most disc herniations occur (Deyo, NEJM 2016).
Which nerve a disc affects depends on where it presses. A disc pushing back and slightly to one side (paracentral) at L4/L5 usually affects the L5 nerve, and at L5/S1 usually the S1 nerve. A disc pushing out to the side (foraminal) affects the nerve leaving at that level, for example L4 at L4/L5. That is why your clinician tests specific muscles, reflexes and areas of skin: to see whether your symptoms match what the scan shows.
Common words on a lumbar MRI report
| Term on your report | What it means in plain words |
| Disc desiccation or degeneration | The disc has lost some water and looks darker on the scan. Very common with age, often called wear and tear. |
| Loss of disc height | The disc is thinner than the ones around it, usually alongside degeneration. |
| Disc bulge | The disc extends a little beyond the bone edges around a wide part of its rim (more than a quarter). A bulge is not a herniation. |
| Disc protrusion | A more focal herniation, over less than a quarter of the rim, that sticks out less far than the width of its base. Often called a slipped disc. |
| Disc extrusion | Disc material has pushed out further than the width of its base, or has moved up or down. |
| Sequestration | A piece of disc material has separated from the disc completely. |
| Annular fissure (sometimes written annular tear) | A split in the outer ring of the disc. Experts prefer fissure because tear wrongly suggests an injury (Fardon, Spine Journal 2014). |
| Thecal sac indentation or effacement | The disc touches or flattens the fluid-filled sac that holds the nerves. It does not by itself mean a nerve is compressed. |
| Nerve root contact, displacement or compression | The disc or bone touches, pushes aside or squeezes a nerve root. This is the finding most likely to explain leg pain, if it matches your examination. |
| Neural foraminal narrowing (stenosis) | The side opening where a nerve leaves the spine is smaller than usual. Graded mild, moderate or severe. |
| Spinal canal stenosis | The central channel for the nerves is narrowed, often by a mix of disc, joint and ligament changes. |
| Facet arthropathy or hypertrophy | Age-related changes in the small joints at the back of the spine. |
| Ligamentum flavum thickening | A ligament inside the spinal canal has thickened, which can add to stenosis. |
| Osteophytes | Small bony growths at the edges of the vertebrae, common with age. |
| Spondylolisthesis | One vertebra has slipped forward on the one below. Graded by how far it has slipped. |
| Modic changes (type 1, 2 or 3) | Changes in the bone next to a disc. Type 1 reflects swelling in the bone and is the type most often linked with back pain; types 2 and 3 are longer-standing changes. |
The experts who agreed these terms stress that they describe anatomy only. They do not say what caused a finding, whether it is causing symptoms, or what treatment is needed (Fardon, Spine Journal 2014).
A bigger herniation is not always worse news
It sounds backwards, but larger herniations are more likely to shrink on their own. A review of pooled studies found that, on repeat scans, shrinkage was seen in 96% of sequestrations, 70% of extrusions, 41% of protrusions and 13% of bulges (Chiu, Clinical Rehabilitation 2015). How a scan changes does not always track how you feel, which is another reason to judge progress by symptoms and function.
The same scan can be reported differently
In one study, a single patient had a lower back MRI at 10 different centres within three weeks. Between them the reports listed 49 different findings, and not one finding appeared in all 10 reports (Herzog, Spine Journal 2017). It was one patient, but it shows why a report is a starting point for a conversation, not a final verdict.
Words matter too. When lumbar MRI reports included a short note on how common these findings are in people without pain, patients were less likely to be prescribed opioid painkillers (McCullough, Radiology 2012).
Did I need an MRI?
For most new back pain, no. US doctors' guidance advises against routine imaging unless there are warning signs, because early scans did not improve outcomes and can lead to more tests and treatment (Chou, Annals of Internal Medicine 2011). An MRI is useful when there are signs of nerve damage or serious disease, when symptoms persist despite good care, or when an injection or surgery is being planned. Repeat scans are rarely needed just to check progress (Jensen, BMJ 2019).
When a report needs prompt attention
Speak to a doctor promptly if your report mentions compression of the cauda equina, severe canal stenosis, a fracture, infection or a mass. Go to a hospital emergency department straight away if you have any of these:
- Numbness around the genitals, anus or inner thighs
- New trouble passing urine or controlling your bladder or bowels
- Leg weakness that is quickly getting worse, or sciatica in both legs
Questions to ask about your report
- Does what the report shows match where I feel my symptoms?
- Is a nerve being compressed, and does my examination show that nerve is affected?
- Which findings are normal for my age?
- Is anything here urgent?
- Does this change my plan, and what would make us review it?
How BP Chiro uses your MRI
Bring your report, and the images if you have them, to your first visit. Your clinician will examine you first, then go through the report with you, explain which findings are likely to matter and which are common for your age, and build a plan around both. If anything on the scan or in your examination needs a doctor or spine specialist, we will tell you and refer you.
Related reading:
- Sciatica: what it is, how long it lasts and what helps
- Slipped disc: symptoms, MRI and non-surgical options
- Lower back pain: causes, warning signs and non-surgical care
Have your MRI explained in Kuala Lumpur, Johor Bahru or Penang
Every first visit at BP Chiro starts with a full spinal assessment. Choose the clinic nearest you:
- Chiropractor in Johor Bahru (Uda Utama and Johor Jaya)
- Seri Kembangan, for south Kuala Lumpur, Puchong and Putrajaya
- Kepong, for north Kuala Lumpur
- Kluang
- Penang
- Chiropractor Johor Bahru
- Chiropractor Kuala Lumpur
References
- 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.
- Jensen MC, Brant-Zawadzki MN, Obuchowski N, Modic MT, Malkasian D, Ross JS. Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med. 1994;331(2):69-73.
- Deyo RA, Mirza SK. Herniated lumbar intervertebral disk. N Engl J Med. 2016;374(18):1763-1772.
- 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;14(11):2525-2545.
- Chiu CC, Chuang TY, Chang KH, Wu CH, Lin PW, Hsu WY. The probability of spontaneous regression of lumbar herniated disc: a systematic review. Clin Rehabil. 2015;29(2):184-195.
- Herzog R, Elgort DR, Flanders AE, Moley PJ. Variability in diagnostic error rates of 10 MRI centers performing lumbar spine MRI examinations on the same patient within a 3-week period. Spine J. 2017;17(4):554-561.
- McCullough BJ, Johnson GR, Martin BI, Jarvik JG. Lumbar MR imaging and reporting epidemiology: do epidemiologic data in reports affect clinical management? Radiology. 2012;262(3):941-946.
- Chou R, Qaseem A, Owens DK, Shekelle P. Diagnostic imaging for low back pain: advice for high-value health care from the American College of Physicians. Ann Intern Med. 2011;154(3):181-189.
- Jensen RK, Kongsted A, Kjaer P, Koes B. Diagnosis and treatment of sciatica. BMJ. 2019;367:l6273.