Signal abnormality
Read Your Scan Editorial Team·Last updated
Written from published radiology references and reviewed for plain language. Not written or signed by a physician, and not a diagnosis. How we write these pages →
In plain language
An area of an MRI that is brighter or darker than the tissue around it should be. "Signal" is MRI's word for brightness — an abnormal signal says something differs there, without yet saying what.
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Where you'll see this
MRI findings, usually with the sequence named ("T2 signal abnormality").
Your report may word it “Abnormal signal”, “Signal change” or “Altered signal”. These mean the same thing.
Questions worth asking your doctor
- In plain terms, how big or how serious is what you are describing?
- Does this description point to one likely cause, or several?
- Does anything here explain the symptoms I came in with?
How often does this turn up?
Signal abnormality is one of MRI’s most-used and least specific phrases, and it appears across reports of every body part. MRI does not measure density; it measures the signal tissue gives back, and each sequence makes different tissues bright or dark. When an area does not give back what that tissue normally gives back, the radiologist calls it a signal abnormality — a statement that something looks different from expected, deliberately without saying what.
Does it mean something is wrong?
The phrase is chosen precisely when the appearance does not identify itself, so on its own it is neither reassuring nor alarming. Its meaning comes entirely from what follows: which sequences show it, where it is, what shape it is, whether it enhances, and whether it was there before. Bone marrow signal abnormality after an injury is usually bruising; the same phrase about the spinal cord means something quite different. A radiologist who could name the cause would name it, so the phrase is best read as an honest description rather than as a veiled hint.
What to do with it
Because it describes uncertainty, the next step is usually whatever reduces it. Comparison with previous imaging is the most valuable and the cheapest, since something unchanged over years rarely needs pursuing. Otherwise: additional sequences, contrast, a follow-up scan at an interval, or occasionally a different test. If your report uses this phrase and nothing has been arranged, that is worth asking about directly — not because it is alarming, but because the phrase itself leaves a question open.
Frequently asked questions
- Is a signal abnormality serious?
- The phrase alone does not say, which is why it is used. It means an area looks different from what that tissue normally looks like on MRI. Everything that determines seriousness — location, size, pattern, behaviour with contrast, change over time — is described separately.
- Why does the report not name what it is?
- Usually because the images genuinely do not identify it. MRI shows how tissue behaves rather than what it is made of, and several different causes can produce the same appearance. Naming a cause the images do not support would be worse than describing what is actually visible.
- What is bone marrow signal abnormality?
- A change in the signal from inside the bone, most often from fluid in the marrow. After an injury it usually means bruising, which resolves over weeks to months. It is also seen with wear at a joint surface and with several other causes, so the report describes the pattern and context around it.
How a finding is described
Where this word comes up
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