Ask an Expert: Can you have a stroke and not know it?

Q: Is it possible to have a stroke and not know it, like if you're sleeping or the symptoms are mild?

Answer from Ted Lowenkopf, M.D., medical director of Providence Stroke Center:

Yes, you can have a stroke and not know it. A stroke's effects can be undetectable if the stroke is small or if the tissue damaged does not serve a critical function. Evidence of the stroke would show on a CT scan or an MRI of the brain, but it might not produce symptoms.

But you really may be asking if a stroke can occur without your realizing, at the time, that it's happening – such as when you are asleep or when the effects are minor. Let’s look at those two scenarios separately.

Generally, minor stroke symptoms won’t rouse you from sleep. But when people do wake up after a stroke, they notice something is amiss. The symptoms depend on both the severity of the stroke and the region of the brain it damaged. Perhaps one leg does not seem to work well, or an arm feels weak. People may have double vision or a partial or, rarely, complete loss of their field of vision. They may feel dizzy or unsteady walking down the hall. They may seem confused or unable to retrieve the words they want to say, or their speech may be slurred.

A time for action
If you happen to wake during the night and suspect a stroke, do not turn over and go back to sleep, hoping all will be fine in the morning. Call 911. Don't worry about disturbing your physician or causing a ruckus with the family or in the neighborhood. Dedicated professionals are waiting for your call. A rapid response to stroke symptoms is critical. Time is brain!

Prompt evaluation, determination of the type of stroke and proper treatment can make the difference between recovery and long-term disability. The first three hours after a stroke are a critical opportunity for beginning treatment with tPA, our most-effective treatment for ischemic strokes. “Ischemic” means the stroke was caused by a clot clogging a blood vessel in – or leading to – the brain. About 80 percent of all strokes are ischemic.

tPA, which is delivered intravenously, dissolves the clot, re-opening the blood vessel. Administering it as early as possible within the first three hours after symptom onset maximizes the chances for dissolving the clot and decreases the chances of disability from stroke. The drug carries the risk of causing bleeding in the brain after a stroke, but it does not increase the risk of death.

Hospitals carefully evaluate patients before giving tPA; only three to five percent of ischemic stroke patients nationally receive it. The main reason for not receiving this treatment is arriving at the ER too late, beyond the three-hour time window. Other reasons for non-treatment include mild or spontaneously improving symptoms.

Timing is everything
As you can imagine, the timing issue poses a problem if the stroke occurs when a person is asleep. For safety's sake, we define the stroke onset time as the time the patient was last known to be “normal” (without new stroke symptoms). So, if you went to bed at 11 p.m. and woke up at 7 a.m. with a problem, we say the stroke happened at 11 p.m. If you went to bed at 11 p.m., got up for a drink of water at 5 a.m. without a problem, and woke up at 7 a.m. with a problem, we say the stroke happened at 5 a.m.

Whatever the timeframe, the same advice holds true: Call 911 for immediate medical care. If intravenous tPA is not appropriate – either because of the timing or the type of stroke – we can try other treatment strategies, including devices that can extract clots. Our goal is to restore the flow of blood to try to limit the damage.

Mild stroke is a warning
Your question about a mild stroke is a good one. Let's say you have a mild stroke or temporary symptoms caused by transient ischemic attack (TIA), often called a "mini-stroke." A TIA occurs when the blood supply to the brain is temporarily interrupted or cut off, resulting in a sudden, brief decrease in brain function.

Symptoms can be subtle and fleeting: They typically last less than an hour. The advice for these milder events is the same: Call 911, right away, for urgent evaluation and care. If you have a mild stroke or TIA, do not assume that you have dodged the bullet. In fact, a TIA is a warning that you are at high risk for a full-blown stroke, which could occur anywhere from minutes or hours to days later.

A recent study showed that five percent of patients with TIAs will have a stroke within 48 hours. A TIA requires urgent medical attention. If you have a stroke or TIA, work with your health care provider to determine whether you have risk factors that need to be addressed.

Factors that may increase your risk of stroke include high blood pressure, high cholesterol, diabetes, smoking, more-than-moderate drinking, and any use of certain street drugs, such as cocaine or methamphetamine.

To reduce your risks, you might take antiplatelet medications (aspirin, for example, or blood thinners if prescribed by your physician), stop using tobacco and street drugs, begin an exercise program and work toward a healthy weight. In addition to memorizing the warning signs of stroke yourself, make sure that you have allies looking out for you by informing your family, your co-workers, your neighbors and your friends about the warning signs and the importance of immediately calling 911 if they suspect a stroke.

Signs of stroke
We like to review the signs of stroke at every opportunity. (Notice that they all begin with the word "sudden." That's because strokes occur when blood flow to the brain is interrupted suddenly, whether by a clot blocking an artery or by a rupture in an artery.)

If you experience even one of these symptoms, call 911, pronto:
  • Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
  • Sudden confusion or trouble speaking or understanding
  • Sudden trouble seeing in one or both eyes
  • Sudden trouble walking, dizziness, loss of balance or coordination
  • Sudden severe headache, with no known cause

While it is possible that another medical condition is causing your symptoms, don't bet your life on it. Get an immediate medical evaluation.

For more information, we recommend the American Stroke Association and the National Stroke Association.