I know silly ? But I bet this horse ain't beat to death lol ( I'm new ) personally I would describe it as before sometimes during a attack, I don't know if this is a "shadow" or what   ps. I hope I can delete this later cuz I know its crazy :D

I also have other medical conditions so... it may just be me  :-/

I never described it as a grub worm, my early attack sensations are more of a tendon on the side of my head being pulled tighter then the E string on my guitar! I used to fantasize about taking a knife and cutting the tendon at the base of my neck to relieve all the tension and stop the pain! ;D Yeah, fortunately I never went through with THAT idea. But a grub worm chewing it's way through ...yeah...I can see that description!;)

Joe

Wow good thing you have not tried that... In behind my eye is the worst place for me and I get the idea to pull up my skull by my eye sockets but that is impossible.

I have had that feeling. I even develop a knot ( pea sized on my forehead on the cluster side durring my cycle. As far as the guitar string comparison...I hear ya. I think the clusters tighten some tendons or something in the neck at the base of the skull. Killer isnt it.

I even argued with my doctor that we should just severe that tendon and eliminate most of my pain. Fortunately his learned, educated oipinion won out! ;D

Joe