FLAIR
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
A common MRI image setting that makes some changes in brain tissue easier to see. You may see it named in the report.
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Where you'll see this
This wording turns up on Brain MRI reports — MRI imaging of the brain. A brain MRI shows the brain tissue in fine detail, along with the fluid spaces, blood vessels, and surrounding structures. Doctors order it to look into headaches, dizziness, memory changes, weakness, seizures, or to follow up on other tests. MRI is especially good at showing soft tissue. Many findings it describes are common, age-related, or minor — the report describes what the pictures show, and your doctor interprets what it means for you.
Questions worth asking your doctor
- What prompted this MRI, and did the images address that concern?
- Are any of the findings expected for my age, or do any stand out?
- Do any findings need a follow-up scan, and if so, when?
- Should these results be discussed with a specialist?
- Is there anything I can do to support my brain and vascular health?
How common is this?
FLAIR is an MRI sequence used on essentially every brain study, and its name appears in the technique section. It is a T2-type sequence with the signal from free fluid deliberately suppressed — which in the brain means the cerebrospinal fluid is turned dark instead of bright.
When should I worry?
The sequence name carries no meaning of its own. Its purpose is to solve a specific problem: on ordinary T2 images, bright cerebrospinal fluid sits right next to areas of brain that are also bright, and lesions near the ventricles or the brain surface get lost against it. Suppressing the fluid makes those areas visible. This is why the most commonly reported brain MRI finding of all — bright spots in the white matter — is usually described on FLAIR, and why those reports so often mention the sequence by name.
What happens next
Nothing follows from the sequence being listed. What matters is what it showed, described separately in the findings. A report describing FLAIR hyperintensities in the white matter is describing the finding that is near-universal with age and usually reflects small vessel change — the sequence name tells you how it was seen, not how serious it is.
Frequently asked questions
- What does FLAIR stand for?
- Fluid-attenuated inversion recovery. In practice it means a T2-type image with the signal from free fluid suppressed, so cerebrospinal fluid appears dark rather than bright.
- Why is FLAIR used on brain scans?
- Because bright cerebrospinal fluid on ordinary T2 images hides lesions sitting next to it. Turning the fluid dark makes changes near the ventricles and at the brain surface visible, which is where a great many of them occur.
- What are FLAIR hyperintensities?
- Bright areas on the FLAIR images, most often in the white matter. They are extremely common with age and usually reflect small vessel change. They are frequently graded with the Fazekas scale, which describes extent rather than predicting anything.
Other words on the same report
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