Neck disorders implicated as causes of headache fall into two groups: a) those in which the cervical lesions are unequivocally demonstrable, and in which treatment of those lesions helps the headache; these are widely accepted as causes of headache, and include: congenital and acquired craniovertebral junction disorders, rheumatoid arthritis and ankylosing spondylitis of the upper cervical spine, and dissection or trauma to the carotid or vertebral arteries; b) those in which the neck disorder is either banal or not objectively demonstrable, and which seldom improve following treatment of the neck; these are not widely accepted as causes of headache; they include whiplash syndrome, segmental hypomobility-hypermobility syndrome, the posterior cervical sympathetic syndrome, cervical migraine, third occipital nerve headache, and cervicogenic headache. Features of a headache suggesting its cervical origin are: 1) abrupt onset following sudden excessive movement of the head; 2) persistent unilateral suboccipital or occipital pain; 3) consistent reproduction by neck movements and by nothing else; 4) abnormal postures of head and neck; 5) significant painful limitation of movement of upper cervical spine; 6) abnormal mobility at craniovertebral junction; 7) C2 sensory abnormalities or lower medulla or upper cervical cord signs.