Rupture of the sternocleidomastoid muscle: A case report.

Sternocleidomastoid muscle injury is a rare traumatic lesion of the neck that may mimic several severe emergent conditions. Additionally, it can result in a significant hematoma that compresses vital structures. We herein report the case of a 27-year-old male patient who presented with sudden-onset neck pain following exercise. Ultrasound revealed a linear anechogenic area within the enlarged, relatively heterogeneous, and hyperechogenic left sternocleidomastoid muscle, with a hematoma originating from the muscle and herniating through a disrupted fascia. Contrast-enhanced computed tomography demonstrated a protruding cystic lesion from the enlarged sternocleidomastoid muscle, consistent with a hematoma. The hematoma was mild and did not compress the neighboring structures; therefore, the patient was managed conservatively with analgesics and motion restriction. Awareness regarding the radiological findings of the sternocleidomastoid muscle is essential for ruling out several emergent conditions and determining the extent of the hematoma.