A Lateral View of the Middle Scalene of a Male

Description

Running obliquely from the posterior tubercles of the cervical vertebrae to the superior surface of the first rib, the scalenus medius (middle scalene) is presented in lateral profile with its muscle belly positioned posterior to the scalenus anterior. The interscalene interval lies between them, a corridor where the roots and trunks of the brachial plexus and the subclavian artery pass, while the subclavian vein tracks anterior to scalenus anterior. Posteriorly, the middle scalene blends into the prevertebral compartment, with the levator scapulae and posterior scalene regionally nearby, and the cervical transverse processes anchoring its superior attachments. Clinical relevance concentrates at the thoracic inlet. Hypertrophy, spasm, or congenital fibrous bands at the scalene triangle can narrow the passage for the brachial plexus and subclavian artery, producing neurogenic or arterial thoracic outlet syndrome, classically exacerbated by neck rotation or overhead activity. A clear lateral view also helps orient clinicians during interscalene brachial plexus block, where the needle target sits between anterior and middle scalenes, and where inadvertent spread can affect the phrenic nerve on scalenus anterior. Small space. Big consequences. Use this asset in gross anatomy teaching on the prevertebral musculature, in anesthesia training materials covering cervical fascial planes and regional blocks, or in surgical education discussing supraclavicular exposure at the thoracic inlet and protection of the brachial plexus and subclavian vessels. It also supports patient-facing explanations of scalene-related thoracic outlet syndrome when paired with symptom diagrams. Anatomical accuracy verified by SciePro's Medical Advisory Board.