Etiology The etiology of congenital myotonic neck is still unknown. However, most scholars believe that abnormal intrauterine pressure or fetal malposition is the main cause of congenital myotonic neck. The fetal malposition in the uterus or abnormal pressure on the uterine wall may cause pressure on one side of the neck and local blood circulation in the sternocleidomastoid muscle, resulting in ischemic fibrous degeneration of the muscle and causing oblique neck. Difficult delivery and the use of forceps is one of the causes of myotonic rhomboid. This view has not been conclusively confirmed because it occurs more often in breech births, but examination of the local mass of the sternocleidomastoid muscle did not reveal signs of old hemorrhage. It is thought to be genetically related because of a clear family history in 1/5 of children with this condition, and it is often combined with congenital acetabular dysplasia and other malformations. Pathological changes The sternocleidomastoid masses are mainly striated fibrotic muscle tissue, and the gross specimen resembles a soft fibrous scar with a white cut surface. Microscopic observation shows that it consists of dense fibrous tissue with reduced muscle tissue and reduced transverse lines, and in severe cases the muscle tissue disappears and more scar tissue appears, but there is no bleeding in the muscle. It can be divided into three pathological types according to the proportion of muscle and fibrous tissue presented: 1, muscular type: mainly muscle tissue, containing only a small amount of fibrous degeneration of muscle tissue or fibrous tissue. 2, mixed type: containing muscle tissue and fibrous tissue. 3, fibrous type: mainly fibrous tissue, containing a small amount of muscle or degenerated muscle tissue. This typing has certain guiding significance for the determination of clinical efficacy. In general, the muscle type has better efficacy and the fiber type has poorer efficacy.