What's behind extreme headaches confuses experts, sufferers

Although migraine headaches are notorious for causing pain, they've created a lot of confusion, too. Here are answers to six common questions about migraines.

1. What exactly is a migraine?

The "classic" migraine is preceded by aura, which typically consists of strange visual disturbances -- zigzagging lines, flashing lights and, occasionally, temporary vision loss. Numbness and tingling affecting one side of the lips, tongue, face and the hand on the same side may also occur. But only about a third of migraine sufferers experience aura, and fewer still with every attack.

The migraine headache, with or without aura, tends to produce pain that usually begins (and sometimes stays) on one side of the head. The word migraine comes from the Greek hemi-, for half, and kranion, for skull. A migraine headache often has a pulsating quality to it. Many people also experience nausea, extreme sensitivity to light or sound, or both.At this point, there are no blood tests for migraines. Migraines don't cause brain abnormalities that a CT scan or an MRI can detect, although these tests are sometimes ordered to diagnose other problems that cause severe headaches, such as bleeding in the brain.

The epidemiology of migraine can be helpful in raising, or allaying, suspicions. It's well documented that women are three times more likely to have migraines than men, that the tendency to have migraines runs in families, and that they occur less often as people age. But, obviously, these are guideposts, not diagnostic criteria.

2. What causes a migraine?

There is near-total agreement that migraines originate in the brain. One prevailing theory is that migraines are caused by rapid waves of brain cell activity crossing the cortex, the thin outer layer of brain tissue, followed by periods of no activity. The unwieldy (and potentially confusing) name for this phenomenon is cortical spreading depression.Cortical spreading depression makes sense as a cause of aura, but researchers have also linked it to headache. Proponents cite experimental evidence that suggests it sets off inflammatory and other processes that stimulate pain receptors on the trigeminal nerves. This "neurogenic" inflammation and the release of other factors make the receptors -- and the parts of the brain that receive their signals -- increasingly sensitive, so migraine becomes more likely.

3. What triggers a migraine?

There are too many triggers to list them all here. Many migraine sufferers are sensitive to strong sensory inputs like bright lights, loud noises and strong smells. Lack of sleep is a trigger, but so is sleeping too much, and waking up from a sound sleep because of a headache is a distinctive characteristic of migraine. Many women have menstrual migraines associated with the drop in estrogen levels in the days just before and after menstrual bleeding begins. Alcohol and certain foods can start a migraine.

One of the most common triggers, stress, is one of the hardest to control. Migraines tend to start not during moments of great stress but later on, as people are winding down.

4. Do migraines cause strokes?

Numerous studies show that migraine with aura is a risk factor for stroke, and that migraine without aura probably is not, or is minimally so. Researchers have also found that people who have migraines with aura are at increased risk for accumulating small infarcts -- areas of dead brain tissue resulting from inadequate blood supply. Still, there's a reluctance to claim that migraines definitively cause strokes.

5. How can migraines be prevented?

With the possible exception of losing weight if you're heavy, there isn't much known about how to prevent migraines if you've never had one.

But if you are prone to migraines, there are steps to take to prevent or diminish the attacks. Often the first is identifying triggers so you can avoid them. That can take time and real detective work.

Keeping to a regular, stress-reducing schedule that includes a full night's rest, balanced meals and exercise can make a difference. In fact, anything that reduces stress -- yoga, meditation, exercise -- can help.

People who are sensitive to light tend to react more to the red end of the spectrum, so wearing blue- or green-tinted glasses helps fend off an attack.

If nonpharmacological changes don't help, medications may. The drugs most commonly prescribed for preventive purposes are beta blockers, tricyclic antidepressants and anticonvulsants. All have side effects, so they should be taken at low doses and only if migraines are frequent.

6. How can they be stopped?

It used to be that migraine sufferers had no choice but to take refuge in a dark, quiet place and wait it out. The drugs available to abort an attack weren't very effective and had bad side effects. Now many people cut an attack short with one of the triptan drugs, a class that includes eletriptan (Relpax), sumatriptan (Imitrex) and zolmitriptan (Zomig).

The triptan drugs seem to work by inhibiting pain signaling in the brainstem, but they also constrict blood vessels. For that reason, people with a history of cardiovascular disease (heart attack, stroke, uncontrolled hypertension) are usually advised not to take them.

Pain relievers like ibuprofen (Advil, Motrin) and naproxen (Aleve) can halt a mild attack, but rebound headaches may develop if they are taken too often.