The Anatomical Structure of the Middle Scalene of a Male

Description

Arising from the posterior tubercles of the transverse processes of C2 to C7, the scalenus medius descends as a long, lateral cervical muscle to its insertion on the superior surface of the first rib, posterior to the scalene tubercle. Anterior to it lies the scalenus anterior, while the levator scapulae sits more posteriorly, with the prevertebral fascia investing the deep surface. The brachial plexus roots and trunks and the subclavian artery pass inferiorly in the interscalene interval between the anterior and middle scalene muscles. A narrow corridor. Clinically, this anatomy anchors the concept of thoracic outlet syndrome, where hypertrophy, spasm, or fibrous bands at the scalene triangle can compress the subclavian artery or irritate the brachial plexus, producing arm paresthesias or exertional ischemic symptoms. It also matters in regional anesthesia: interscalene brachial plexus block targets the nerve roots in the groove adjacent to the middle scalene, and needle trajectory is planned to avoid vascular structures while respecting the muscle planes and fascia. Palpation and ultrasound identification of scalenes are common points of failure for trainees. Use this asset for teaching lateral neck musculature in gross anatomy and regional anatomy courses, for anesthesiology and pain medicine materials on ultrasound-guided interscalene block, and for surgical or rehabilitation publications discussing cervical muscle spasm and neurovascular compression at the thoracic outlet. It also supports patient-facing education on neck posture disorders when paired with diagrams of the brachial plexus. Anatomical accuracy verified by SciePro's Medical Advisory Board.