Although the causes of migraine headache pain are not well understood, the actual process is fairly simple. Blood vessels located just outside the skull dilate. These vessels are surrounded by coils of nerve fibers, and when the vessels expand, the nerves are stretched, resulting in pain and inflammation. The resulting migraine headache pain can be completely debilitating, causing secondary symptoms such as vomiting and sensitivity to sound and light.
A number of factors might be responsible for causing migraine headache pain. Women are more likely than men to suffer migraines, and hormonal shifts during their cycles might trigger attacks. The condition appears to be hereditary as well, with most people suffering their first attacks during childhood or early adulthood. Diet, alcohol consumption and stress contribute as well. Even with all of these factors in place, a migraine is not guaranteed, but it does become much more likely.
When these factors do conspire, one or both of the temporal arteries, the blood vessels located along the outside of the skull at the temples, begin to expand. This process is called vasodilation. With each attack, the location of the migraine will vary, sometimes on one side, sometimes the other, and occasionally both.
The temporal arteries are surrounded by a coil of nerves, and when an artery expands, it exerts pressure on these nerves. Dilation stretches out the nerve tissue, and the nerves respond by sending pain impulses and releasing chemicals. These chemicals cause inflammation, making the blood vessels expand further, applying more pressure and causing more intense pain.
Blood pumps through the arteries, rippling swells along the vessel’s surface. With each pulse, the nerves are stretched even further. This is why migraine headache pain is typically described as thumping or pounding.
In addition to pain relayed directly from these nerves, migraines often trigger reactions from the sympathetic nervous system, the network responsible for the fight-or-flight response. Sympathetic reactions cause symptoms unrelated to the inflammation. Nausea, vomiting and diarrhea commonly occur alongside migraine headache pain. Sufferers might also experience painful sensitivity to light or sound and might need to rest in a dark, quiet room until the headache passes.
Sympathetic reactions might also delay digestion. During a migraine, the stomach might wait longer before emptying into the intestine. Although this does not add to the migraine headache pain experienced by the sufferer, this does mean that oral painkillers will not reach the bloodstream as quickly, delaying relief from pain and slowing recovery.