What Happens During a Migraine Attack ?
Abnormal electrical activity may occur in the brain tissues during a migraine attack . Areas of altered activity have been found on brain imaging studies in patients having migraine attacks . This activity is called " spreading depression ," and it represents a wave of increased activity of nerve cells , followed by decreased activity . Originally , it was thought that blood vessel spasms caused this abnormal activity , but more recently , we have learned that this is not the case . The electrical disturbance is the primary event , and the blood flow changes are a response to the electrical disturbance .
The tendency to generate this electrical disturbance is probably enhanced by inheriting certain forms of the ion channels that set the electrical activity in these nerve cells . Ion channels are like chemical gates – they control the flow of sodium , potassium , and other elements in and out of nerve cells . Migraine may represent a set of biochemical abnormalities of these gates . In a sense , individuals with abnormalities are " primed " to generate this abnormal electrical activity . The addition of something else may push them over the edge and generate the electrical disturbance that underlies migraine attacks . This is where other triggers come to play a role : certain foods , weather changes , stress , hormonal changes , sleep disruptions , etc .
The electrical disturbance may cause obvious symptoms . For example , spreading depression in the vision areas of the brain may result in unusual visual phenomena such as the appearance of spark-like bursts , wavy lines , blind spots , or even complete visual loss in rare cases . Abnormal cortical brain activity over other regions of the cortex can result in temporary confusion , inability to speak , numbness , or even paralysis of any part of the body . These symptoms , which occur due to electrical disturbances at the surface of the brain , typically are brief , lasting no longer than 20 minutes .
The electrical disturbance of migraine frequently involves deeper parts of the brain that are important processing centers for the senses . We believe that these centers become " hypersensitized ." This means a person having a migraine who senses pain , motion , or sound will tend to have an exaggerated , distorted experience of the pain , motion , or sound that may be so intense that it is difficult to tolerate . A hallmark of migraine headache – rare but telltale when it happens – is allodynia , the experience of just simply touching the scalp or even the hair as intolerably painful . Light , sound , motion , or odors can also become intolerable . The patient may become so sensitive