What causes a Headache?
You may say, “I know what causes my headaches. Staying up late or drinking too much coffee will bring on a headache every time”. But a trigger is not the same as a cause. Aged cheese, cigarette smoke, alcohol, excessive caffeine, bright sunlight, disrupted sleep patterns, and many other factors can trigger headaches in some migraine or headache–prone patients. However, even a known trigger does not always lead to a headache. Therefore, these factors cannot be said to be a cause of headache the way a particular virus is the cause of a head cold or flu. Instead, the nervous system of the headache sufferer is somehow predisposed to respond to these triggers and other stresses with a series of biochemical changes that result in the pain and other symptoms of headache.
Until recently, medical researchers believed that tension–type headache was caused by contraction of muscles of the head and neck, and that migraine headache resulted from the expansion (or dilation) of blood vessels in the brain and scalp. The migraine aura was thought to be due to a constriction of the blood vessels, which preceded the dilation and which reduced blood supply to the eyes and brain. These theories made sense to both physicians and patients, since they accounted for the tenderness and the throbbing experienced with these forms of headache, as well as the visual disturbances of aura. However, the vascular (involving blood vessels) theory could not explain many of the other symptoms of migraine, including the mood changes before and after the attack, and the nausea and vomiting that occur during the attack.
The use of new noninvasive technology, such as MRI, PET and CT scans, along with the great advances in understanding the brain’s biochemistry, have taught us much more about the causes of head pain. As we now know, vascular changes may be an important factor in a headache attack, but they are not the whole story nor the root cause. A reduction in brain activity, rather than blood supply, seems to be linked to the migraine aura. Similarly, there is little evidence that muscle contraction causes tension–type headache. Some researchers think that several stages in the complex pain–producing process are similar for these two distinct headache disorders.