What causes congenital muscular torticollis?
Congenital muscular torticollis may occur following a difficult birth, especially if the infant is very large or is delivered breech. During the delivery, if the sternocleidomastoid muscle, the neck muscle that extends from the jawbone (mastoid) to the clavicle (collarbone) and sternum (breastbone), is stretched or pulled, it may tear, causing bleeding and bruising within the muscle. The injured muscle develops fibrosis (scar tissue) which causes the muscle to shorten and tighten, pulling the infant’s head to one side. The fibrosis forms a mass or lump that sometimes can be felt on the side of the neck. Occasionally, congenital muscular torticollis occurs because of a defect in the development of the sternocleidomastoid muscle, or because of an abnormal fetal position in the uterus.
