Temporal Arteritis, sometimes called Giant Cell Arteritis, causes severe headache. This often affects just one side of the head. It is caused by inflammation of the blood vessels that supply blood to the head. In some cases there is pain in the shoulders, neck and low back as well. It is important to diagnose the condition promptly because, if left untreated, it can lead to permanent loss of vision. With proper medication the patient typically gets rapid relief of headache and maintains normal eyesight.