I have been getting Botox injections for migraines for six or seven years or more. My husband talked to someone at the gym who had migraines and was being treated by a plastic surgeon in my city whose girlfriend had bad migraines. This started his interest in using Botox in this way. He said they first realized there might be a connection when migraine sufferers who had brow lifts often reported that their headaches stopped after the procedure, which involves cutting the muscle between the eyebrows - the same muscle that is paralyzed by Botox injections.
I was having migraines at least twice a month, and they always lasted three days. It was frustrating to lose so much time, and to be in so much pain. It has worked great for me. At first, I had to get the shots every 4 months, but by now, I can go 8 or 9 months before the migraines return.
Of course different people have different migraine triggers, and hormones seem to be involved in some way, but my experience has been great.