@denheels Welcome to Connect. I am not a patient who had migraines, but I had an ACDF at C5/C6. Muscles spasms in the occipital muscles on the back of the head and neck are similar to migraines and certainly could add more pain to an existing migraine. I know for me, when I get a pain on the back of my head on one side, this is a cue that I need to check my cervical alignment because I can have cervical vertebrae rotate on their own with a spasm just a bit which causes that headache, and straightening it all out resolves that. I worked with a PT on this because I have thoracic outlet syndrome in addition which causes one side of my neck to be too tight which causes this issue.

Have you considered working with a physical therapist? I do think that may help.