There are many different causes of headache, but one of the most prevalent and easily treated is called 'tension headache'. It is called this because tight neck muscles grip the back of the skull (occiput) causing headpain. These muscles can pull on the connective tissues which run from the back of the head to the front, producing pain around the eyes and forehead.
Teeth grinding (bruxism) and other TMJ (tempero-mandibular joint) related problems may cause headache and neck pain. Temporalis, the muscle that closes the jaw, sited above the temples is usually implicated in these problems.
Treatment to these affected muscles and associated neck joint stiffness can be very effective in improving these cases of chronic headache.