You might want to explore this website about upper cervical adjustments -
a page link to get you started -
http://www.upcspine.com/self.htm

After any head hit/injury I think this is one the first things to check, I wish I had known about it 40 yrs ago... my horse dumped me on my head..
I think I would have less problems now if this treatment was well known/accepted back then.
But I think it is still not a mainstream treatment..