Congenital muscular torticollis

Note: Muscle fibers are separated by scar-like fibrous tissue.

The etiology of congenital muscular torticollis is unclear.
Birth trauma or intrauterine malposition is also considered to cause damage to the sternocleidomastoid muscle in the neck.[citation needed] This results in a shortening or excessive contraction of the sternocleidomastoid muscle, often with limited range of motion in both rotation and lateral bending.
The head is typically tilted in lateral bending toward the affected muscle and rotated toward the opposite side.
The reported incidence of congenital torticollis is 0.3-2.0 %. Sometimes a mass (a sternomastiod tumor) in the affected muscle may be noted, this appears at the age of two to four weeks, it disappears gradually, but sometimes the muscle becomes fibrotic.
It is likely to disappear within the first five to eight months of life.
The condition is treated initially with physical therapy, with stretching to correct the tightness, strengthening exercises to achieve muscular balance, handling to stimulate symmetry. A TOT Collar is sometimes used. About 5–10% require surgery, "surgical release" of the muscle if stretching fails.