One of the easiest cases for a chiropractor is a person who presents with headaches. A majority of headaches are caused by misalignments of the neck bones (subluxation) which cause pressure on the nerves which start from the neck and go up to the head. So really what is going on is that you have a problem in one area of the body causing pain in another. Unfortunately, most of the pain syndromes, have similar origins.
An excellent study in the Journal Cephalagia in February 2002 clearly demonstrated the connection. In this study, the researchers injected anesthesia into the joint between the first and second bone in the neck of 34 subjects. 60% of those patients got rapid, complete relief on their headache pain after the injection. I estimate had they injected the next joint up as well, they would have had an even better response.
Couple this fact with the tremendous amount of deaths and injuries caused by pain relievers, it only makes sense to see a chiropractor if you your neck is the cause of your headache problem.
This is further confirmation what the chiropractic profession talked about 117 years ago. When you have a pain in your head, look to the neck first.