Brain scans for issues such as headaches, cognitive problems or dizziness have become more common in recent years. But in searching for a suspected condition, doctors are sometimes finding an unexpected one: silent strokes.
These strokes, which experts estimate affect 8 million to 11 million Americans each year, do not cause symptoms but appear on scans as white spots, scarred tissue from a blockage or tiny areas of bleeding vessels — and they should be treated to prevent a full-blown stroke, according to new guidance from the American Heart Association/American Stroke Association.
The scientific statement published Thursday in the journal Stroke.
Although there’s not enough research about these symptomless strokes to warrant mass screening for them, the unintentional discoveries should be taken seriously, said Eric E. Smith, M.D., who chaired the group that wrote the statement.
“It is important to go to your family physician if there are concerns about neurological symptoms like weakness or speech difficulty because silent strokes put people at risk not only for future symptomatic strokes but also for cognitive decline and dementia,” said Smith, an associate professor of neurology at the University of Calgary in Alberta, Canada.
“Radiologists should report it and clinicians need to act on it,” he said.
“The big question becomes, what do you do with it?” said neurologist Philip B. Gorelick, M.D., who helped write the statement. “This paper is very timely to answer practical questions,” said Gorelick, medical director of Mercy Health Hauenstein Neuroscience Center in Grand Rapids, Michigan.
MRI is best at detecting silent strokes, according to the statement. Its use for brain imaging has gone up dramatically over the years to investigate concerns about memory and cognition, stroke, dizziness, unusual headaches or Parkinson’s disease, Gorelick said. He sees people “every day” who have abnormal brain scans that indicate a silent stroke.
“Finding silent strokes or other signs of vascular disease is not uncommon as people get older,” Smith said.
Silent strokes are much more common than strokes that cause classic symptoms such as face drooping, arm weakness and speech difficulty and affect nearly 800,000 Americans each year.
According to the statement, one in four people over 80 have one or more silent strokes. For example, the type of silent stroke that causes white spots in the internal part of the brain, known as white matter hyperintensities, is “a phenomenon that occurs with age, kind of like getting wrinkles or getting grey hair,” Smith said. It is more common among smokers and people with high blood pressure or diabetes, he said.
Although the neurological issues typically have no obvious symptoms, experts said a detailed medical history sometimes uncovers imbalance or clumsiness in a limb that lasted a few days before getting better. But the person never went to the doctor.
“These silent strokes aren’t so silent,” Gorelick said.
After an abnormal brain scan, the patient should be evaluated for risk factors known to contribute to blood vessel blockages and vascular weaknesses in the brain or other parts of the body, the statement recommends. Such factors include high blood pressure, diabetes, high cholesterol and smoking.
These patients should also be screened for atrial fibrillation, Gorelick said. AFib is a type of abnormal heartbeat that can lead to stroke-causing blood clots.
For people with silent strokes, the statement recommends following stroke prevention guidelines already in place, such as eating a Mediterranean diet, reducing sodium in the diet and not smoking.
But if prior symptoms are uncovered, patients may require blood thinners or medications to lower “bad” LDL cholesterol or high blood pressure, Gorelick said.
Aggressive prevention can reduce the risk of a stroke by 80 percent or more, he said.
Although bleeding can occur with blood thinners or clot-busting medications given to people with microbleeds, the benefit of these medications to prevent strokes appears to outweigh that risk, according to researchers.
“The challenge here is that people’s memories change as they get older, and we struggle as clinicians and patients to separate what should be expected with getting older and what could be the sign of a brain disease,” Smith said.
Smith said future research should focus on understanding how silent brain issues influence the risk of heart attacks and strokes.
Including brain scans in clinical trials could also reveal whether certain medications help prevent silent strokes, Smith said. The challenge is that detection requires costly MRI scans that use powerful magnets that make people with metal devices or who are claustrophobic ineligible for the test.
“By shining more light on this issue we can raise awareness among clinicians and patients,” Smith said.