Hey Milly, Unless you headaches have a large muscular element, unlike classic migraines, I really don't see how Botox is supposed to help. However if you have neck problems, and muscular problems where occipital blocks and trigger point injections have been helpful, the botox is a longer acting version of a block. It has no effect on vascular conditions which are supposed to be the cause of classic migraines, but I think often that DX is used too broadly to descibe any type of severe headache.
Insurance companies are being a bear about payng for it for this use as they haven't run the clinical trials for the off label uses it could be efective for.
MY wife has a chiari 1 malformation, it causes head pain and headaches, but the headaches aren't migraine. Initially her insurance covered a few injections but due to the cost, it's been a battle for the last year to use Botox. It was very helpful and less invasive than nerve blocks. There is a less expensive version of Botox A called Botox B. If your insurance won't pay for the botox, your doc can write you a prescription for BotoxB and you can bring the botox to the office for him to administer. This method brings the cost of the botox down to about 350 bucks versus $1200-2K for Botox A injections. Botox B is very similar, it was brought on the market to create a less expensive product available to more people. Chemically it's a slightly different so it's not considered a generic, but the results should pretty much be the same as far as paralyzing muscles that are causing tension type headaches, neck pain, whiplash pain or head pain. Because migraines are vascular in nature, It may be a tough sell to your insurance co since botox has no effect on the CV system.
The last denial from my wifes insurance requested clinical data suportng the use of Botox for Chiari 1, Unfortunately they aren't going to test it for every specifc diagnosis unless they see a huge market. Off label use seems to be a more frequently used reason for drug companies denying paying for many new meds.
Good luck, Dave