One characteristic feature of migraine is that patients recognize certain things that tend to trigger off attacks. For some people it is alcohol, or certain foods. For others it is bright lights, flashing lights, television, very hot baths, strong winds or changes in climate, loud noises, strong smells, excitement, anxiety, shock or sleeping too long. Although this might seem like a very miscellaneous list, it is striking how often migraine patients report the same sort of triggers – especially bright lights and oversleeping. Where stress is a factor, the migraine attack often develops after the pressure is off – weekend migraines, or ones that spoil the first few days of any holiday, are commonly reported.
Migraine attacks usually begin between the ages of 20 and 30, but there are a few unfortunate people who develop migraine in childhood. Sometimes children suffer more in their stomachs than in their heads, with vomiting as the main feature of an attack. They may have these bouts of vomiting without any head pain at first, only developing a one-sided headache as they grow older.
As a result of extensive research into migraine, doctors have a fairly clear idea of what happens during an attack. They know that there are two distinct phases. During the first one, the blood vessels throughout the body – including those in the brain – become constricted. In the second phase, there is a ‘backlash’ reaction, and the blood vessels open out (or dilate) more than is normal. It is the expansion of blood vessels, in the brain, during the second phase, that causes the pain. The premonitions of migraine, which some sufferers feel, occur during the first phase, and may be caused by a reduced blood
flow to certain parts of the brain as the blood vessels narrow.
Playing a central part in this reaction are tiny ‘cells’ in the blood known as platelets. These are very numerous – there are 15 million of them in a single drop of blood – and their main function is to help the blood clot around a wound. During clotting the platelets clump together and release a substance called serotonin or 5HT that makes the blood vessels constrict. This reduces blood flow so that less blood is lost from the wound.
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