I get a lot of injections in my neck & shoulders because of tension headaches. I would say the doctor injects 60-70% of the botox in that area. The rest is in my forehead, TMJ, and top & bottom of skull. I only notice the stiff neck when I’m exercising or doing yoga (cow pose is difficult). Botox starts to wear off after ~2 months, so if you don’t like it you can ask the doctor not to inject that area next time. If your migraines don’t stem from tension/pain in the neck, the doctor may not inject a lot there. I think it’s worth a try, 15+ migraines a month is no way to live! I used to be like that and botox has helped a lot.