People are often alarmed to hear a physician say that there are “spots” on the magnetic resonance image (MRI) of their brain. These spots have been called “unidentified bright objects” (UBO), “high signal intensity areas” (HSIA), “white matter hyperintensities” and “nonspecific white matter changes.”
How worried should people be about those white matter changes? There is no widely accepted guideline for what is “too much,” though most neurologists have their own personal opinion. Some degree of these changes is expected with age. Ignoring the lesions completely, however, is not the best course of action.
What Causes White Matter Hyperintensities on MRI?
Nonspecific white matter changes likely have more than one cause. These changes have been associated with problems like risk of stroke, cognitive decline, depression and diminished physical function, such as walking. It is not clear that these lesions actually cause these problems, however. They may just signify a relatively diminished state of brain health overall.
Similarly, cardiovascular risk factors like high blood pressure (hypertension) also increase with age. As we get older, blood vessels tend to harden and narrow. This narrowing can lead to heart problems like myocardial infarction, or brain problems like stroke.
Are These Changes the Same as Silent Strokes?
The hyperintensities in the brain are in areas that we would expect if they were due to reduced blood flow. There’s some controversy about how the flow could be reduced. Some have viewed the lesions as being miniature strokes that never caused symptoms. Rather than being full-fledged strokes, in which blood pressure totally and completely stops, these regions could represent something less severe. If blood flow slowed instead of stopped due to local changes in blood pressure, the brain regions would slowly and periodically have their oxygen supply reduced.
What Increases the Risk of these Signal Changes?
Arteries narrow more rapidly in people with hypertension, who are smokers, or drink alcohol heavily. Diabetes and obesity also increase vascular risk. White matter hyperintensities have also been correlated with all of those risk factors. Similarly, factors that protect blood vessels, such as a healthy diet and exercise, is associated with fewer white matter changes in the brain as we get older.
Like many other signs of vascular disease, some people are more at risk for these signal changes on MRI than others. Hispanics and African Americans tend to have more lesions than other populations. Women tend to have more white matter hyperintensities than men.
There tends to be some degree of heritability to these lesions, as well. Many genes have been associated with these changes, though it’s not clear exactly how they are related.
While a certain degree of white matter change is expected with age, that does not mean these changes are completely benign. Increased white matter hyperintensities are associated with higher risk of stroke and dementia, as well as higher mortality in general. This is probably not because the lesions themselves are causing problems. Instead, the risk factors that cause the lesions increase the chances of someone having health problems both inside and outside the nervous system.
How Can I Stop These Spots From Worsening?
MRI findings should always be considered in the context of each individual person. Rather than just focusing on these hyperintensities, it is probably best to consider what risk factors might need addressing. Could your diet stand some improvement? Do you need to exercise more?
When looking at what factors seems to correlate most with these spots in the brain, high blood pressure seems to be the most strongly related. However, studies have had mixed results on how to best manage blood pressure in light of these MRI findings. Some studies show that treating blood pressure helps, and others show no clear benefit.
Even more confusing is that in some situations, a higher blood pressure is associated with a better outcome rather than worse! However, this is probably only true later in life. The theory is that high blood pressure causes blood vessels to thicken. At some point, a normal, lower blood pressure can no longer meet the resistance of the abnormally thickened vessels. Perhaps at some point it is better for the brain to let blood pressure run higher than normal.
However, no research has clearly demonstrated this, and other explanations exist. Maybe the blood pressure medication is having an unknown effect beyond just treating blood pressure. For example, maybe what’s important is just how the medicine affects certain receptors on the vessel, rather than how it changes blood pressure. In this case, only trials looking at specific medications would show a difference.
In short, white matter hyperintensities are an extremely common finding in brain MRI, especially in older people. However, just because these spots are common does not mean they are completely benign. An increased number of hyperintensities has been associated with stroke, dementia, and other problems.
The cause of these changes is complex, but likely represents vascular changes that can be impacted by following the kind of advice we all know we should be following anyway. Keep your blood pressure under control, eat right, exercise, avoid smoking and only drink alcohol in moderation. By following this advice, you may not only address the spots on your MRI, but more importantly, keep your brain and entire body healthy.
Lewis H. Kuller, Alice M. Arnold, W.T. Longstreth, Teri A. Manolio, Daniel H. O’Leary, Gregory L. Burke, Linda P. Fried, Anne B. Newman, White matter grade and ventricular volume on brain MRI as markers of longevity in the cardiovascular health study, Neurobiology of Aging 28 (2007)1307-1315.
Robert I. Grossman and David M. Yousem. Neuroradiology: The Requisites 2nd ed. St. Louis, MO: Mosby; 2003.