Damage to the spine in the nape of the neck, caused when it is suddenly jerked forwards and backwards. It happens usually when the rear of a car in which the victim is travelling is hit in a collision. Injury to the spinal cord occurs in a few cases, with mild symptoms of concussion or contusion of the spinal cord. Concussion of the brain may also occur. However, the chief symptoms are those which result from slight damage to the ligaments, joints and muscles of the spine. One consequence is local pain, as a result of which the muscles can go into spasm (cramp), with more severe pain arising in the nape of the neck, back of the head, shoulders and sometimes in the arms. The movements of the neck are frequently restricted because they worsen the pain. Thus a pattern of symptoms can arise which is difficult to interpret and includes headache, dizziness, fatigue and nervousness. It has become clear that the symptoms are not always related to the seriousness of the injury and that psychological factors also play a part.