You might want to read about upper cervical adjustments {also called atlas/axis or c1 c2 adjustments }

some chiropractors are trained to do this, it 's a very simple thing but can be very important esp if you've had any head/shoulder types of hits or falls.

My chiro adjusts mine as needed - minor car accident, sports, fell off a horse and landed on my head many yrs ago.

more info links -
http://www.google.com/search?q=upper...ient=firefox-a

one good one is this -
SIGN / SYMPTOM CHECKLIST
http://www.upcspine.com/self.htm