Lateral Perspective of the Middle Scalene

Description

Arising from the posterior tubercles of the cervical transverse processes, the middle scalene (scalenus medius) descends to the superior surface of the first rib, positioned posterior to the anterior scalene and lateral to the cervical vertebral bodies in this lateral neck view. The muscle belly sits deep to the superficial cervical fascia and is framed superiorly by the skull base and inferiorly by the thoracic inlet, with the clavicle and scapular girdle providing bony context anterior and inferior to the neck. Posteriorly, its fibers relate to the levator scapulae region, while the cervical rib cage and upper thorax establish the relationship between neck musculature and the first rib. Clinically, this perspective matters because the interscalene interval, bounded anteriorly by the anterior scalene and posteriorly by the middle scalene, is the corridor for the roots and trunks of the brachial plexus and the third part of the subclavian artery as they pass toward the axilla. A tight, hypertrophied middle scalene or a fibrous band at its first-rib attachment can contribute to neurogenic thoracic outlet syndrome, often provoking paresthesias in the ulnar distribution and symptoms exacerbated by overhead activity. It also anchors a key teaching point for regional anesthesia: interscalene brachial plexus blocks target the plexus between the scalenes and can inadvertently affect the phrenic nerve running on the anterior scalene. Deep anatomy. Small margins. Use this artwork for gross anatomy and physical diagnosis teaching on the cervical region, for thoracic outlet syndrome patient education materials, or for surgical and anesthesia texts discussing the supraclavicular approach, scalene exposure, and first-rib relations at the thoracic inlet. Anatomical accuracy verified by SciePro's Medical Advisory Board.