Congenital myotonic neck is commonly referred to as “crooked neck”. It is caused by fibromatosis within the sternocleidomastoid muscle and can be detected at birth or within the first two weeks of life. It is more common on the right side than on the left side, and the lesion can involve all of the muscle, but more often the lesion involves only the proximal clavicular attachment point of the sternocleidomastoid muscle. The masses are largest in the first two months after birth and then remain the same or decrease slightly in size, usually becoming smaller or disappearing over a period of one year. If the mass does not disappear, the muscle will become permanently fibrotic and contracted, which will lead to permanent oblique neck if left untreated. Etiology The immediate cause of this disease is contracture and shortening due to fibrosis of the sternocleidomastoid muscle, but the true cause of fibrosis of this muscle is not known. It may be related to the following factors: 1. congenital sternocleidomastoid dysplasia, which is easily damaged during childbirth. 2. 2, one side of the sternocleidomastoid muscle due to birth injury caused bleeding, the formation of hematoma after the mechanization, followed by contracture. 3, Intrauterine fetal malposition, so that one side of the sternocleidomastoid muscle under excessive pressure, resulting in local ischemia, followed by excessive degeneration, replaced by fibrous connective tissue. The pathological changes of the affected muscle tissues are similar to infectious myositis, so it is presumed that the sternocleidomastoid muscle is caused by aseptic inflammation due to birth injury, resulting in muscle degeneration and scarring, and the formation of oblique neck. 5. It is thought that this disease is related to acute obstruction of the sternocleidomastoid vein at birth. Most scholars now support the theory of local ischemia caused by birth injury or intrauterine malposition. Clinical manifestations The deformity may exist after birth or may appear 2 to 3 weeks after birth. At the beginning of the disease, the head movement is slightly restricted, but there is no obvious oblique neck. On palpation, a hard and painless pyknotic mass can be found, which is oriented in the same direction as the sternocleidomastoid muscle and gradually increases in size within 2-4 weeks, then starts to recede and gradually disappears within 2-6 months. Some of the children do not remain oblique neck; many children with untreated sternocleidomastoid muscle gradually fibrosis, contracture hardening, the formation of hard bundles of paracervical, head due to the pull of contracted muscles and oblique neck deformation, muscle shortening side of the face also deformed. If the deformity is not corrected in time, the facial deformation will increase, and finally the cranial development will be asymmetrical, and the cervical vertebrae and even the upper thoracic vertebrae will have scoliosis deformity. Ultrasonography is the best method of examination. Ultrasound observes the continuity of bilateral sternocleidomastoid muscles and the location and size of the mass internal echogenicity, as well as the relationship with sternocleidomastoid muscles and surrounding tissues. Diagnosis The diagnosis can be made based on the appearance of a hard cervical mass within two weeks after birth, without redness, swelling, heat and pain, with clear and movable borders, and no cervical spine abnormalities on X-ray. Differential diagnosis 1, congenital cervical spine deformity Short and thick neck, reduced mobility, common cervical hemivertebrae, cervical fusion, etc. 2.Atlantoaxial subluxation Mostly in children aged 3 to 5 years old, soft tissue congestion around the cervical spine caused by inflammation of the pharynx suddenly appears with head and neck deviation, restricted movement and tension in the collar muscles. Cervical 1 to 2 subluxations can be seen in frontal and lateral cervical spine opening films. 3.Ophthalmologic disease Children with myopia on one side and hyperopia on the other side may have head and neck tilt to one side. However, there is no contracture of the sternocleidomastoid muscle and no restriction of head and neck rotation. 4.Other cervical disc lesions, spinal cord cavitation, sternocleidomastoid muscle deficiency on one side can cause head and neck tilt. In addition, it should be distinguished from enlarged lymph nodes in the neck, lymphoma, cervical dermatomes, carotid aneurysm and other soft tissue tumors. Complications As the disease progresses, the contracture of the sternocleidomastoid muscle gradually worsens. Secondary deformities of the head and face are aggravated, the affected face shrinks, the two eyes are not in the same plane, the rotation of the jaw to the affected side is limited, the sternocleidomastoid contracture is striped, the skull development is deviated and small, and the shoulders are uneven. Treatment 1, non-surgical treatment Under the guidance of the physician, the parents should perform passive neck pulling activities for the child, first pulling the head to the healthy side, then turning the jaw to the affected side, each movement slowly. In addition, the affected side should be fixed on the mother’s chest while breastfeeding. When teasing the baby, standing on the affected side is also a way to pull the sternocleidomastoid muscle. After about one year of conservative treatment, 76% to 86% of the children can be corrected. 2.Surgical treatment After conservative treatment is ineffective or untreated children over 1 year old, because the muscles have been fibrotic, facial deformities appear, and only through surgery can their deformities be corrected. The best age for surgery is from 1 to 5 years old, and for those who are over 5 years old, it is more difficult to recover the facial deformation due to the heavy secondary deformation.