What causes migraine headaches?

While there are a variety of triggers for migraine headaches doctors say the most common factor in whether or not you’re going to have migraines is family history. If your mother or father had migraines, chances are good you will too. Watch this video to learn more.

While researchers are not completely sure what causes a migraine headache, it’s believed to be the result of a complex cyclic contact between the cranial blood vessels and the trigeminal nerve.  A "trigger," such as food, stress, or fatigue, activates neurons that are in charge of releasing a selection of neuropeptides (substance P and neurokinin A). Substance P helps nervous system cells send messages to each other about painful stimuli. It is thought that when substance P levels are elevated in the body, they may produce higher levels of pain. The release of these chemicals causes an increase in blood flow to the brain. The distended blood vessels and the inflammatory response stimulate the trigeminal nerve to send out impulses back to the brain for processing, resulting in a migraine headache.

Doctors are not certain what happens when a trigger causes a migraine, or precisely what happens in the brain. The current theory is that a migraine is caused by a progression of things:

• You encounter a trigger: Let's say you did not eat breakfast and lunch was late.

• The nociceptors in your brain stem, which are pain-sensing cells, pick up on the change in your return and release a chemical called neuropeptides.

• This chemical the attacks other pain-sensing cells which are nearby and they release neuropeptides.

• Some of the chemicals begin to work on muscles surrounding the blood vessels near the surface of your brain. The muscles relax, which makes the blood vessels dilate and causes more blood to flow. This is the stage where doctors believe the aura in a classic migraine develops.

• Some nueropeptide chemicals cause the skull vessels to begin leaking, which makes the tissue around the area swell

Doctors believe that a combination of swelling braining tissue, increased sensitivity and swelling blood vessels is what causes migraines.

The most common triggers that stimulate migraines are stress, weather changes, alcohol, changes in dietary or sleep patterns, and hormonal fluctuations, which cause "menstrual migraines" in some women. Other factors, such as caffeine, aged cheese, bright lights, exertion, smoke, and noise, are also triggers for some people. Triggers can be difficult to identify because it may be twenty-four to forty-eight hours between the trigger and the headache. Also, a particular factor may trigger a headache at some times but at other times may not. Many women have migraines when they are premenstrual but have them less often at other times.

Considerable evidence supports an association between migraine headaches and instability of blood vessels. The mechanism of migraine can be described as a three-stage process: (1) initiation, (2) prodrome (time between initiation and appearance of headache), and (3) headache. Although a particular trigger may be associated with the onset of a specific attack, it appears that initiation depends on an accumulation of several triggers over time. Once a critical point of susceptibility (or threshold) is reached, a "cascade event" is initiated, setting in process a domino effect that ultimately produces a headache. Food allergies, histamine-releasing foods, alcohol (especially red wine), stress, hormonal changes (e.g., menstruation, ovulation, birth control pills), and changes in weather (especially changes in barometric pressure) are some common triggers of migraines.

Experts aren't sure what causes a migraine headache and—when it occurs—an aura. For many years, scientists believed that a tightening of the cerebral arteries interfered with blood flow. The arteries would then dilate to compensate, not only in the brain but also outside the brain, where the dilation causes inflammation. Although scientists still believe that this combination of blood vessel dilation and inflammation causes migraine headache, they no longer think that the tightening of cerebral arteries underlies the aura.

Although researchers have confirmed that the aura coincides with a reduction in brain blood flow, this reduction isn't consistent with blood vessel constriction or spasm because these conditions would have a more substantial effect. Instead, many experts now suspect that the migraine aura is produced by a neurological phenomenon known as spreading depression, which is a wave of decreased electrical activity (indicating lower brain cell functioning) and diminished blood flow that inexplicably washes across the cerebral cortex. As neuronal communication is suppressed, cerebral blood flow diminishes. The areas of lowered activity gradually spread, as if washing across the brain, causing the symptoms of aura.