Jun 18, 2014 3 min read

DEAR DOCTOR K: I regularly get terrible migraine headaches. My doctor has prescribed medication, but I still think I should have a brain scan to make sure there’s nothing more serious going on.

DEAR READER: Severe headaches cause both misery and fear. Obviously, the fear is that something serious, like a brain tumor, may be causing the headache.

Still, the pain of even a severe headache rarely comes from something catastrophic like a tumor. I spoke to my colleague Dr. Egilius Spierings, a neurologist at Harvard-affiliated Brigham and Women’s Hospital, about migraines and brain scans.

He said that fear of a sinister, unidentified cause often drives people to get brain scans. According to a report published in the journal JAMA Internal Medicine, about one in 10 people who seek care for severe headaches end up having a brain scan. The great majority of the scans find nothing wrong.

Brain scans themselves are not risk-free. Repeated computed tomography (CT) scans, for example, expose you to radiation that can raise the risk of cancer down the road. Scans can also lead to more scanning if the test turns up something strange — even though many of these findings do not turn out to be dangerous. Only a very small percentage of brain scans reveal something abnormal. And most of these “abnormalities” just look a little odd — they won’t affect your health.

You and your doctor should focus on finding an effective treatment for your migraine headaches. If he or she has not already prescribed them, ask your doctor about triptans. These drugs can stop a migraine within two hours if you take the drug when the headache is still mild. If your migraine doesn’t stop within two hours, your doctor should direct you to take more medication. Also ask your doctor about other medications that can help prevent future migraine attacks.

So when might a brain scan be in order? Red flags that should cause you to talk to your doctor include:

— Not having had headaches before. Migraine headaches often begin early in life. They can be really severe, sending a person to bed. But if today’s headache is just like, and just as bad, as your typical migraines, it is very unlikely to be due to something else. Be concerned if you’re over age 50 and start having headaches for the first time.

— Headaches that worsen over a few weeks. Migraine attacks typically end completely in hours or days. Be concerned if you have a headache that is with you all the time, day after day.

— A headache that comes on in seconds. A brain hemorrhage — a potentially very serious cause of headache — typically begins like a bolt out of the blue. Five minutes ago you were perfectly fine, and now you’re in agonizing pain.

— Headache associated with fever.

— Headache associated with weakness of a part of the body, new difficulty with balance or feeling confused.

Most headaches, even really bad ones, won’t benefit from a scan. But watch for the danger signs I’ve mentioned; they could require a scan.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.