Hello: I Suffer 1 To 2 Times Per Week From

hello:
I suffer 1 to 2 times per week from VERY severe migraines, do to extreme head trauma (cracked skull and brain stem separation - during traffic accident 8 years ago).
I have gone through the list of dietary modifications and adhere to fully them (especially no caffeine or alcohol). I have tried all over the counter migraine meds - no relief. The only thing which worked was Xanax. However, it is not recommended to rely on Xanax for extended period of time (I was on it .5mg 3x/day for over 1 year, Xanax did relieve the headaches. I do not take Xanax anymore do to possible addiction risks. What is the best prescription medication for severe migraine headaches?