En español | Usually, a headache is … well, just a headache.

"Ninety-five percent of the time, even an agonizing headache is not serious and doesn't mean you have a brain tumor," says Brian M. Grosberg, M.D., associate professor of neurology at the Albert Einstein College of Medicine and codirector of its famed Montefiore Headache Center, in the Bronx, N.Y. "An over-the-counter pain reliever, a cup of coffee or a nap usually brings relief."

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Pounding headache? Don't dismiss it — it could be a sign of a more serious problem. — Photo by Christopher Robbins/Getty Images

Still, severe headaches can be frightening because — sometimes — they are a sign of a serious condition, one you don't want to minimize or misdiagnose. How can you tell whether it's a true headache emergency? Here are 10 red flags to watch out for. If you ever spot one, call 911 or get yourself (or your loved one) to an emergency room — stat.

1. It's the worst headache you've ever had. One of the first things Grosberg teaches his medical students is that when people use this sort of language about a headache, they must be seen immediately. Called a "thunderclap headache," this sudden, excruciating pain, which reaches maximum intensity within seconds to a minute, may signal the rupture of a brain aneurysm, when a blood vessel in the brain tears, cutting off the blood supply to a part of it. Brain aneurysms can be treated, but only if you get to the ER within hours of an attack.

2. You have neurological symptoms. A headache coupled with confusion, dizziness, memory loss, slurred speech, loss of balance, weakness on one side of the body, seizures or blurred or double vision could signal a stroke or brain tumor, so always demand prompt medical action.

3. You're 50-plus and this is your first-ever acute headache. Throbbing migraines since college may be incapacitating, but they're not as worrisome as a first-time headache in an older adult, which, if severe, could signal a stroke or brain tumor.

However, keep in mind that the symptoms of a brain tumor vary greatly, depending on a tumor's size, location and type. Although many people believe that a severe early-morning headache coupled with nausea or vomiting is a sure sign of a tumor, studies have found that's true in less than 50 percent of cases. Indeed, most patients with these types of symptoms have a tension headache instead.

4. You've had bad headaches before, but this one is different. Any major change in the type or pattern of your headaches should be checked out right away. This could signal a number of conditions ranging from life-threatening (stroke, tumor or meningitis) to less serious "rebound" headaches caused by too much pain medication.

5. You have a fever, stiff neck or vomiting. These symptoms along with a headache could point to meningitis — a swelling of the membranes lining the spinal cord and brain. Although both the bacterial and viral forms of this illness are relatively rare in older people, both can be fatal. Older patients with meningitis may not have the telltale stiff neck common in younger people. Their symptoms often include the confusion and loss of consciousness that closely resemble a stroke.

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