Headaches are one of the more common ailments I see in my office on a daily basis. They range from minor irritation to full blown disability. The tricky thing about working with headaches is that there are so many things that can cause a headache. By far, however, the most common cause of headaches is neck dysfunction.
A headache that is caused by dysfunction in the neck is called a cervicogenic headache (cervico = neck, genic = derived from). It is estimated that 70% of all headaches are cervicogenic and that many other headaches are often triggered as a result of neck dysfunction. Based on the patients I treat with headaches I would concur.
When the neck becomes dysfunctional through injury or slow progressing trauma like posture, the nerves that exit the spinal cord in the neck get irritated. This irritation is transferred to the structures innervated by the neck like the muscles that connect the head to the rest of the body and the blood vessels that go to and from the brain. When these structures do not function as a result of improper nerve signals, they send a warning system in the form of pain, muscle spasm and either increased or decreased blood flow.
So, one of the best ways to treat headaches is to improve the function of the neck. Chiropractic is the best thing I know of to help improve joint and thereby nervous system function. More than likely when these things are taken care of, the patient either has a marked decrease in either the frequency or the severity of their headaches or the headaches resolve altogether.