Which muscle is affected in congenital torticollis?

• A. Sternocleidomastoid
• B. Deltoid
• C. Clavicular
• D. Trapezius

Answer: (A)

Congenital torticollis is caused by shortening or fibrosis of the sternocleidomastoid muscle on one side. This tight SCM pulls the head toward the affected side and rotates the chin to the opposite side, which is the characteristic posture seen with this condition. The sternocleidomastoid is the muscle that governs neck rotation and lateral flexion, so it is the one that becomes involved. The other muscles listed don’t produce this neck posture: the deltoid moves the shoulder, the trapezius primarily moves the scapula and supports neck extension, and the clavicular option refers to a portion of the SCM rather than a separate neck-muscle issue. Therefore, the sternocleidomastoid is the muscle affected.