Congenital torticollis is most commonly caused by benign fibrosis of the sternocleidomastoid muscle. Absence of the sternocleidomastoid
muscle is a rare cause of congenital torticollis. There have been fewer than a dozen reported cases of agenesis of the sternocleidomastoid
muscle. We describe a case of congenital absence of the sternocleidomastoid diagnosed by US and confirmed on MRI.
Keywords Sternocleidomastoid - Agenesis - Sternomastoid