These are headaches caused by dysfunction in the cervical spine (neck). There is a relay station that lies in the upper cervical spinal cord which houses two neural pathways. One pathway supplies sensation to the front of the head/face and the other pathway supplies sensation to the back of the head. If there is a problem in the upper neck such as tight muscles, stiff/inflammation joints, irritated local nerves, it triggers this relay station causing referred pain into the head and/or forehead.
The headache usually occurs on one side and is accompanied by reduced and/or painful range of motion in the neck. Cervicogenic headaches respond well to Chiropractic care as by loosening up the muscles and joints in the upper neck it helps to restore normal joint and muscle function taking pressure off the pain sensitive structures causing the headaches.