Have had surgery for chiari 1 and been decompressed still have migrains & severe headaches they want to do botox shots is this safe? does it work ?

Yes and yes: Headaches can be a multifactorial problem. A portion of the headache may have been due to the chiari malformation and a portion can be for other reasons. Botox injections do help with stress related headaches in some patients. Please talk to a headache specialist to see if this is right for you.

Perhaps: You need to see a medical headache specialist; it is unlikely that the chiari was the cause of your pain. Botox is safe and effective if administered to the right patient by someone who is trained to do the injections.