Pediatric myotonic neck, also known as crooked neck, is a condition caused by contracture of the sternocleidomastoid muscle on one side, which is characterized by head tilt and forward tilt to the affected side and face rotation to the healthy side. Most scholars believe that it is related to injury: one side of the sternocleidomastoid muscle is injured and bleeding during delivery due to extrusion by the birth canal or forceps, and the contracture is formed by hematoma and myelination; some believe that the fetal head position during delivery obstructs the blood supply to one side of the sternocleidomastoid muscle, causing ischemic changes in the muscle. Another theory is that it is due to the head deflection of the fetus to one side in the uterus, unrelated to the birth process. Symptoms: After birth, the child is found to have a mass on one side of the neck, with the head tilted to the side of the muscle contracture and the jaw turned to the opposite side. In most children, the mass can be palpated and is located in the middle and lower part of the sternocleidomastoid muscle on the affected side. The masses are relatively hard, some larger, some smaller, and vary in shape from oval to striated. The head is tilted to the affected side and the face is rotated to the healthy side, and the face is deformed over time.