Headaches and Your Neck.
For some headache patients, the three nerves that exit the top of the spine (upper neck) may be at least partially responsible for their headaches. These three nerves travel into the head and have to pass through a very thick group of muscles in the upper part of the neck near where these muscles attach to the base of the skull. This is why when you have headaches and rub the neck, the muscles may feel tight and or tender. In fact, if enough pressure is applied over one of these three nerves, pain will radiate into the head following the course of the nerve, sometimes all the way into the eyes. When chiropractic treatment is applied in the upper neck region, a reduction of the headache and neck pain may occur because the muscle tension is decreased and joint motion is restored.
Steve Yeomans, D.C., April 2010