What happens in the head during a migraine attack? 

Migraine comes when arteries in the brain first shrinks and then expands. With appropriate medication artery elasticity is restored and the worst discomfort during an attack may be removed. There is no specific treatment which removes the migraine once and for all, but preventive medicine may be given to migraineurs who are severely affected. 

There are several theories about what happens in the head when we have migraines. 

The simplest theory is that blood vessels in the brain shrink due to 'something'. It may be a drop in estrogen levels in the blood of women or vasoconstricting biogenic amines (tyramine, phenylethylamine and perhaps histamine). When arteries are narrower than usual, and the same amount of blood pushes through,  the blood pulls at the walls in the blood vessels (called shear stress). It causes the blood vessel walls to release the substance NO (nitric oxide), which causes blood vessels to expand. The expansion also means that the blood vessels leak a little blood plasma and we get, in popular terms, a blister between the brain surface and meninges. Meninges are very sensitive to pain, and we get migraines. 

Triptans act on blood vessels, so they restore their normal diameter. 

A slightly more complicated theory says that the nuclei in the brainstem release amines, which then affect blood vessels elsewhere in the brain. This model fits nicely withthe hypothesis that migraine possibly can be triggered  irregular sleep, jet lag, and light and noise. Also, migraineurs tend to lack 'habituation' (ie. persistently detect noise or repetitive visual impressions such as flickering light) fits nicely into this model. The model can also explain that, along with a migraine attack, we may experience mood changes. And finally, there is excellent agreement with the observations that persons with hemiplegic migraine  often have changed regulations in the  absorption and release of positive ions (Na +, Ca + + and K +) from the neurons. The model also explains why, for example whiplash accidents can trigger migraines, as the nuclei of the brain stem, which release amines, can be damaged by such injuries. 

So far we have not achieved a full understanding of every detail of the migraine mechanisms. But the two models are compatible, ie. they can both be right, and  each opens for a host of new questions. We must wait for the answers just yet.

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