Teena,
We have an article here, Intradermal Botox for Migraine, Headache, Pain Disorders. There's a link near the bottom of the article to the original research poster too. There are many, many articles in medical journals. Good journals to look in are Headache and Cephalalgia. You can research on PubMed.
Ask someone at your insurance company if they'll pay for amitriptyline, gabapentin, and verapamil. I'll bet they say, "Yes," and there are as many studies on Botox as there are on those medications.
There are over 100 medications in use for Migraine prevention, yet only 4 of them are FDA approved. I can't really prove it, but I suspect that insurance companies don't want to pay for Botox because of the cost.
Good luck,
Teri