Clinical manifestations: A hard oval mass in the lower part of the sternocleidomastoid muscle is often found in newborns 7-14 days after birth, which can gradually increase in size. After two months, the mass begins to shrink and finally disappears completely, and the muscle becomes an inelastic fibrous cord. It is also common for the muscle at the mastoid process to be cord-like. The head is gradually pulled to the affected side, the neck is twisted, the face is tilted, and the jaw is tilted to the healthy side. If left uncorrected, the affected side develops more slowly, resulting in gradual deformation of the face and skull and asymmetry on both sides, which can be known by measuring the distance from the outer canthus of both eyes to the corner of the mouth; the occipital, cervical and upper thoracic vertebrae are visible in the posterior view, showing scoliosis deformity. In patients who have not been treated for a long time, other muscles on the affected side of the neck also develop corresponding contractures, and the cervical vertebrae gradually undergo morphological and structural changes. In this kind of advanced myotonic squint, even if the contracture of the sternocleidomastoid muscle is corrected, it is difficult to restore the normal shape of the face.