system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5- What happens in the brain during a migraine and why does it hurt so much?
gpt
We do not understand the mechanism of pain in migraines. Migraines feature waves of decreased activity in the brain. The waves are different for everyone, and so are the symptoms. A classical migraine starts at the back of the brain. The back of the brain controls the eyes, so people get eye symptoms. The waves then spread forward across the brain over minutes. The face control area is the next affected, people get a tingly face. The waves spread further forward, and as more of the brain is involved, the parts of the body that that section of the brain is sends and receives signals from get symptoms, with a tingling feeling passing down the arm and leg over minutes as more of the brain is involved. If the muscle part of the brain is involved, the limb controlled by that part of the brain can become temporarily paralised. Finally, the front of the brain can be can get depressed, and people can lose the ability to talk, or they may become confused. We do not know exactly why the depression of brain activity occurs, or why pain follows. The depressed parts of the brain have restricted blood flow, but the brain activity depression precedes the decrease in blood flow. This means that it is not squeezing in the blood vessels *italics*causing*italics* decreased activity in the brain, rather decreased activity causing less blood to flow there. Medicines that relax the muscles in the walls of veins and arteries have some effect in making migraines better, so it could be something do with pain sensors in those blood vessels activating (the brain itself has no pain sense nerves).