In 2004, doctors reported the first case of "airplane headache" in the medical literature; three dozen more cases were documented in the following years.

The unusual head pain is specific, researchers say: severe pain, usually on one side of the head and near the eye, that flares up during an airplane landing.

Whether "airplane headache" is a distinct condition is still up for debate.

But Italian researchers are arguing that it should be considered a new subtype of headache.

In a recent article in the medical journal Cephalalgia, they report on another 75 people with complaints that fit the signs of airplane headache.

And they suggest a list of criteria that doctors can use to diagnose it.

Whether airplane headache will be officially recognized is anyone's guess. Doctors go by a detailed classification system, called the International Classification of Headache Disorders, to diagnose specific subtypes of headache.

"Is (airplane headache) a unique disorder? I think it is. But others might disagree," said Dr. R. Allan Purdy, a neurologist and professor at Dalhousie Medical School in Halifax, Canada.

Classifying airplane headache as a distinct disorder would allow it to be studied more directly, according to Purdy, who wrote an editorial on the report.

"Nobody knows what causes it," Purdy said. "Nobody knows how many people have it. Nobody knows what treatments work."

Further research would presumably help answer those questions.

In this most recent report, researchers led by Dr. Federico Mainardi, of Giovanni e Paolo Hospital in Venice, describe the cases of 75 people with symptoms suggestive of airplane headache.

Those individuals had contacted the doctors -- mostly by email -- after reading about a case of airplane headache Mainardi's team had published in 2007. The researchers had all these people complete detailed questionnaires to delve deeper into their symptoms.

Overall, respondents' symptoms fit the features of past cases of airplane headache -- severe pain on one side of the head that was usually limited to the time when the plane was landing.

The headache was almost always short-lived -- less than 30 minutes for 96 percent of people. Only a minority consistently had headaches during airplane landings; for most, it happened on some flights but not others.

There are limitations to the report, Mainardi and his colleagues acknowledge.

Except for three of the possible airplane-headache sufferers, who had physical exams, the rest were assessed long-distance.

Purdy agreed that that's a shortcoming -- and said that some people in the group may well have had other reasons for their head pain.

But taken along with earlier case reports, Purdy said he thinks there's enough evidence to suggest that airplane headache may be a "new and unique disorder."

It's not clear what, precisely, might trigger headaches during airplane landings. But one theory is that the pain may be related to pressure changes in the sinus cavities. (It's known, for instance, that airplane passengers with colds or sinus infections can get severe headaches during take-off or landing.)

Another question is why only some passengers would succumb to airplane headaches.

But Purdy pointed out that just over half of the people in the current report also had a history of other headache problems -- including migraines and frequent tension headaches.

So people who are already vulnerable to headaches may be at greater risk.

But Mainardi's team says airplane headache is distinct from migraines and other well-known headache types.

One of their diagnostic criteria is that the pain can't be linked to other causes.

They also say a person should have had at least two attacks of severe head pain during flight, with the symptoms lasting no more than 30 minutes. And there should not be any other symptoms -- like nausea or sensitivity to light or noise, which may be signs of migraine.

But if you think you're getting airplane-related headaches, Purdy suggested bringing it up with your doctor. You may at least be able to rule out other causes of the pain.

And if you do have true airplane headaches, the good news is that they seem harmless, though unpleasant.

"It doesn't appear to be a serious or life-threatening disorder," Purdy said -- noting that that's also true of most headaches.

No one, however, is sure how to prevent airplane headaches.

Of the 75 people in this report, 29 said they'd tried taking medication to head off their pain. The tactic was a success for 11 of them -- with over-the-counter painkillers, like aspirin, naproxen and ibuprofen, being the most common choice.

SOURCE: bit.ly/L3spx5 and bit.ly/MfdyRp Cephalalgia, online April 5, 2012 and May 23, 2012.

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