Can you be in doubt?
 

I was just wondering if headache from head injury comes from the nerves or muscles on the outer skull or from the brain itself at impact with the inner skull. Would you be able to get a headache without concussion? and the other way around, could you get a concussion without a headache?

If you wouldn't get a headache from concussion I believe it would be very difficult to distinct between a concussive blow and sub-concussive blow. Some say you could never be in doubt if you had a real concussion, is this true? I hope it is, since it would be horrible to get multiple concussion syndrome without even realizing, which I believe would be possible if it wasn't the brain generating the headache but rather the surrounding nerves leaving you dependent to receive a hard blunt blow before the nerves kick in.

It might be a combination of both nerves and brain, I dunno, that's what I am really curious about.

Trigger points & muscle spasms can also cause headaches..