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What Is a Silent Stroke?
You may not know it’s happened, but the damage to the brain is real
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What’s scarier than having a life-changing medical emergency? Having one and not knowing it.
That’s the case with what’s known as a silent stroke.
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A silent stroke occurs when blood flow to the brain is blocked or cut back, depriving brain cells of oxygen in the process. But unlike the more well-known ischemic and hemorrhagic strokes, a silent one shows none of the initial symptoms that signal a stroke is happening and you need to get to the ER pronto. Those warning signs include slurred speech, arm weakness, face drooping, a change in vision or loss of balance.
Although a silent stroke goes unnoticed, “an absence of symptoms doesn’t necessarily mean an absence of brain injury,” says Mitchell Elkind, M.D., chief science officer for brain health and stroke at the American Heart Association.
People who’ve had one may eventually experience problems. Silent strokes, Elkind says, “can still damage the brain and accumulate over time.”
Here’s what you need to know.
Who is most at risk of a silent stroke?
Like an ischemic stroke, a silent stroke is caused by a blood clot that interrupts blood flow in the brain, as opposed to a hemorrhagic stroke, which is characterized by bleeding in the brain.
“The absence of symptoms is usually due to the fact that the stroke is very small, so not enough brain tissue is damaged to lead to a deficit or symptoms,” Elkind says.
“It could also be due to the location of the stroke in a part of the brain that isn’t responsible for functions, such as strength, sensation or language, that would be obvious to the person experiencing the stroke,” he adds.
For every stroke with noticeable symptoms, 10 silent strokes occur, on average, according to the American Stroke Association. The risk is greater for older adults (around 1 in 4 people over age 80 have had a silent stroke).
It’s also higher in people with atrial fibrillation, or AFib. This irregular heartbeat disorder increases the risk of silent stroke more than threefold. People who smoke or have a history of vascular disease, both of which affect blood vessels, are also at higher risk.
Is a silent stroke serious?
The absence of obvious symptoms doesn’t mean an absence of harm to the brain. Although the damage is often minor, it can be permanent and contribute to several age-related conditions, such as cognitive decline, dementia, an unsteady gait, incontinence and depression.
“Silent strokes often don’t occur in isolation,” Elkind says. They can add up over time. “Even if small, they can be a warning sign that a bigger stroke will follow. In this respect, a silent stroke is like a TIA [transient ischemic attack, or mini-stroke], a harbinger of bigger problems. Although each one damages a small part of the brain, cumulatively those multiple small injuries can add up.”
How is a silent stroke diagnosed?
Usually by accident. “Doctors usually diagnose silent strokes by finding evidence of brain damage on imaging like an MRI or CT scan that’s done for other reasons. For example, someone is having memory problems or is getting a brain scan after a car accident,” says Hera Kamdar, M.D., an assistant professor in the Department of Neurology, Division of Cerebrovascular Disease and Neurocritical Care, at Ohio State University’s Wexner Medical Center.
“The pattern of brain damage, and the person’s history of risk factors, usually help us determine the cause of the brain damage,” Kamdar adds.
What’s the treatment for a silent stroke and how are they prevented?
Since silent strokes are almost always diagnosed well after the fact, treatment usually focuses on managing risk factors for a subsequent stroke. Any type of stroke, silent or otherwise, raises your risk for another one.
You can help prevent a silent stroke by doing all the things you’d do to reduce your chances of having any kind of stroke. That includes giving up cigarettes if you smoke, keeping blood pressure levels in the healthy range and managing cholesterol and blood sugar levels, Kamdar says. Maintaining a healthy weight and exercising are important as well.
Granted, there’s not a lot you can do about genetic risk factors, but maintaining a healthy lifestyle goes a long way toward reducing your overall risk for stroke.
“Control of risk factors, especially high blood pressure, is the best way to prevent strokes large and small, prevent cognitive decline associated with aging and preserve brain health,” Elkind says.
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