Botox as a Chronic Migraine Preventative

Hello, I'm posting this on behalf of a friend who doesn't have a Reddit account:

Does anyone have experience using Botox as a preventative for chronic migraines? I'm curious as to your experience with both effectiveness and the side effects of the treatment.

I’ve tried and failed every class of preventative and my migraines are too frequent for effective usage of abortives. My neurologist is suggesting I try Botox next. I'm also 19, so I'm worried about long-term use side-effects particularly too.

Thank you!