How does Botox treatment for migraines work?

So no one really knows the exact answer. There's some theories. One theory is that it decreases muscle contraction, that decreases irritation of nerves. The other theory is that, and this is only shown in animals, so in mice, I think, so they think that some of the nerves that are on the inside of the skull come out through the sutures where the bones on the skull meet, and they think that Botox travels through those nerves and gets into the brain and prevents release of a chemical called CGRP, which is one of the main neurotransmitters involved in migraine pain.