Understanding Migraine Headaches: Six Key Factors

Harvard Health

Migraine pain usually begins on one side of the head. The word migraine comes from the Greek hemi-, for half, and kranion, for skull

Although migraine headaches are notorious for causing pain, they've created a lot of confusion, too. We hope the answers to the six questions below will clear up a few misunderstandings and provide some useful information along the way.

1. WHAT EXACTLY IS A MIGRAINE?

Some people use the term migraine to describe any severe headache, but not all severe headaches are migraines nor are all migraines severe, although many do live up to their reputation for excruciating pain.

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. But, as with aura, one has to be careful about generalizing: Some studies have found that about 40 percent of migraineurs have headache pain on both sides of the head, not just one, and children with migraines usually have pain on both sides.

It's also possible to confuse other sorts of headaches with migraines. Migraines can cause nasal congestion and a runny nose, so they're sometimes mistaken for sinus headaches. And the regular headache that most of us have experienced can have some of the features of a migrainous one, such as unilateral pain and nausea.

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.

In short, arriving at a definition and diagnosis for migraine is complicated. Yet a simple headache diary -- keeping track of headaches and factors that might have provoked them -- can be very helpful in making a diagnosis.

2. WHAT CAUSES A MIGRAINE?

For years, doctors believed that migraine headaches originated with the blood vessels, particularly those that supply the meninges, the thin membranes wrapped around the brain inside the skull. It was thought that when those blood vessels widened -- dilated is the medical term -- they impinged on pain receptors on the lacy network of trigeminal nerves that service the meninges and other parts of the head.

According to this vascular theory, aura was caused by low blood supply from the narrowing of those blood vessels before they rebounded and widened, causing pain. The vascular explanation had considerable intuitive appeal because of the pulsating quality of migraine headaches. Some doctors elaborated on the theory, assigning different sorts of pain to different blood vessels.

But now there is near-total agreement that migraines originate in the brain, not with the blood vessels that surround it. 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. A Brazilian researcher, Aristides Leão, first observed it in rat brains in 1944, but many studies since have confirmed it occurs in the human brain, as well.

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.

Some leading researchers have expressed doubt about whether migraines start with cortical spreading depression. Experimental drugs that inhibit cortical spreading depression have been developed, but study results reported in 2009 for one of the most promising, a drug called tonabersat, showed a preventive effect on aura, but not on migraine headache.

So, say some researchers, migraines are best explained as beginning lower in the brain, in the brainstem. This "primitive" region of the brain controls basic functions, such as respiration and responses to pain, and modulates many others, including incoming sensory information. The theory is that if certain areas of the brainstem aren't working properly or are easily excited, they're capable of starting cascades of neurological events, including cortical spreading depression, that account for migraine's multiple symptoms.

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. Interestingly, migraines tend to start not during moments of great stress but later on, as people wind 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.

The association might be there because migraine with aura and stroke may share a common cause. People who have migraines with aura are strongly encouraged to avoid adding other stroke risks on top of it, such as smoking or oral contraceptives.

5. HOW CAN MIGRAINES BE PREVENTED?

Migraines are not like heart disease, a condition with many risk factors that we can modify to lower our chances of getting the disease in the first place. 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 many steps to take to prevent or diminish the attacks. Often the first is identifying triggers so you can avoid them. That can take some 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.

The alternative medicines used for prevention include feverfew, coenzyme Q10, magnesium, and riboflavin -- and that's just the tip of the iceberg. Judging by studies, none of them is a surefire bet, but that doesn't mean they won't work for some individuals.

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're taken too often. Rebound headache occurs after the body gets used to having a medication in its system; when it's not there, headaches happen. Migraines can quickly snowball into more serious pain, so it's important to treat the headache early, regardless of the medication. - Harvard Health Letter

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