White matter hyperintensities are bright spots that show up in the deeper part of the brain on an MRI scan. White matter is the tissue that carries the wiring between the thinking regions of the brain, and hyperintense just means bright on that kind of image. They are among the most common findings on an adult brain scan, and they turn up more often with every decade of life.
Here we explain what the bright spots are, how common they are at any age, and when they point somewhere else.
Why the spots look bright
Two settings on the MRI scanner, written on reports as T2 and FLAIR, are tuned so that tissue holding extra water glows white.
White matter that is worn or mildly damaged holds a little more water between its cells. That patch then lights up against the darker tissue around it.
Water shows bright, and with that one sentence you can translate your own report. Where it says hyperintense on T2 or on FLAIR, the scanner found a patch holding more water than its surroundings. The brightness says nothing by itself about the cause.
They become more common with age
By later life, most people who get a brain MRI have some of these spots. Among people scanned for a medical reason, about 17% of those under 50 had at least one, and from 80 on close to 90% did. So a report from someone in their seventies or eighties puts the finding with the majority rather than outside it.
What causes white matter hyperintensities
Wear on the smallest blood vessels
Very thin arteries run deep into the brain and feed the white matter. Over the years they stiffen, narrow and leak a little, and high blood pressure speeds that up. The tissue they supply then gets slightly less blood than it needs. It loses a bit of its insulating layer, and extra fluid moves in, which the scanner picks up as a bright spot.
Doctors call this slow wear small vessel disease, and white matter hyperintensities are its most visible sign. If you see that name on the report, it points at this process, a common companion of aging rather than a rare illness.
Spots the report calls nonspecific
Nonspecific is a word you may well find on your own report, and it is less ominous than it sounds. It means the spot is really there, but its look does not point to any one cause.
How often that happens depends heavily on age, and it flips as the decades pass. In younger adults most spots never get a named cause, which is the expected result rather than a workup that fell short. From 80 on, almost all of the spots found are judged to come from small vessel disease. By then that wear is the obvious explanation.
Causes that come up less often
A smaller number of these spots have another origin. If you have had migraine for years, a few small spots are common and rarely cause any trouble. Multiple sclerosis can also produce bright spots, though in a different pattern. In that condition the immune system attacks the insulation around nerve fibers. Rarer causes include inflammation of the blood vessel walls, inherited conditions that affect the small vessels, and earlier radiation treatment to the head.
Other names for the same finding
Reports use several names for the same finding. White matter hyperintensities describes what is visible on the scan. The other names add an assumption about the cause. The commonest in current reports is chronic microvascular ischemic change: small blood vessels, getting less blood than ideal, over a long time.
Leukoaraiosis is an older term for the same bright areas and is going out of use. If your report carries one of these phrases instead, you are reading about the same thing.
Whether the spots cause symptoms
Many people never notice anything. They often turn up by chance, on a scan ordered for a headache, dizziness or an injury.
When the changes are more widespread, they can go along with slower thinking, trouble finding words, an unsteady or shuffling walk, and low mood. These are general signs with many possible causes, so they do not prove the spots are to blame. There is no neat rule that a certain number of spots produces a certain symptom. That is why the finding is meant to be read together with how the person actually feels and copes.
What the finding does not mean
Not automatically multiple sclerosis
Many people first hear of multiple sclerosis through bright white matter spots. On its own, though, this line on your report is nowhere near enough for that diagnosis, which rests on a specific pattern. The damaged areas have to sit in certain places, and there has to be proof that they arose at different times. The 2024 update to the criteria spells out how to tell the two apart in people over 50. Age-related spots are common enough by then to muddy the picture.
Not a stroke that already happened
A stroke happens when the blood supply to part of the brain is cut off suddenly. It leaves a different mark: a defined area of damage in the territory of one blocked vessel. These spots are scattered and build up slowly over years, so finding them on your report does not mean an unnoticed stroke has occurred. Strokes can be small, and some do pass unnoticed at the time. That is one reason a radiologist looks at the pattern rather than at any single spot.
Not dementia
Small vessel changes do often sit alongside the conditions that cause dementia, and they can add to the burden on the brain. Widespread changes are a signal worth taking seriously. But having bright spots is not a diagnosis of dementia, and most people who have some do not develop one. Dementia is diagnosed from how a person thinks and manages daily life over time, not from a scan picture alone.
Whether the spots can be reversed
Spots of the common age- and blood-pressure-related kind generally do not disappear. The tissue change behind them does not undo itself, and no treatment currently makes them go away. Bright areas from other causes behave differently: where inflammation or swelling settles with treatment, the spots can fade or vanish.
Blood pressure changes how fast new spots appear, and no other factor has stronger evidence behind it. In a randomized trial, tighter blood pressure control slowed that down. After about four years the changes had grown in both groups, but measurably less with the tighter target. So tighter control slows the pace at which new spots form, without clearing the ones already there.
When a closer look is warranted
Three things move this finding out of the routine group.
One is a nerve symptom alongside it. Numbness or tingling that will not settle, weakness, unsteadiness, a change in bladder or bowel control. Blurred or lost vision in one eye with pain on moving it counts too.
Another is a report that names where the spots sit rather than calling them scattered and nonspecific. A radiologist reads named places differently from scattered ones, because some locations fit a particular cause and are worth following up.
The last is new or growing spots on a repeat scan. That is why a second MRI is sometimes suggested even when nothing needs treating now.
Without any of those three, two questions matter for the doctor who ordered the scan. Do the spots fit the usual age-related pattern? And is blood pressure where it should be?
A scan captures a single day. So a symptom that comes and goes is worth writing down while it is happening, with the date and what it felt like.
Sources
Neuroimaging standards for research into small vessel disease: advances since 2013. Lancet Neurology, 2023. Source
Prevalence of white matter hyperintensities and radiological cerebral small vessel disease: an insight from routinely collected data. BMC Neurology, 2025. Source
Association of intensive vs standard blood pressure control with cerebral white matter lesions. JAMA, 2019. Source
Clinical significance of magnetic resonance imaging markers of vascular brain injury: a systematic review and meta-analysis. JAMA Neurology, 2019. Source
Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. Lancet Neurology, 2025. Source
