Middle Scalene, Gross Anatomy

Description

Running along the lateral cervical spine, the middle scalene (scalenus medius) arises from the posterior tubercles of the transverse processes of C2 to C7 and descends inferolaterally to the superior surface of the first rib, posterior to the subclavian groove. Anterior to it sits the anterior scalene, while posteriorly it blends into the deeper muscular contour near the posterior scalene and the levator scapulae as that muscle tracks down toward the superomedial scapula. Cervical vertebrae, the occiput and temporal bone, and portions of the clavicle and scapula frame the muscle’s course in a right lateral view. Clean landmarks. Clinically, the interscalene interval between the anterior and middle scalenes is the corridor for the roots and trunks of the brachial plexus, and its relationship to the first rib is central to neurogenic thoracic outlet syndrome and to traction injuries in the lateral neck. This lateral perspective also supports teaching of the interscalene brachial plexus block, where needle placement targets the fascial plane adjacent to the middle scalene while avoiding pleura at the lung apex and limiting spread toward the phrenic nerve on the anterior scalene. Scalene hypertrophy, postural rib elevation, or fibrous bands can narrow this space and reproduce paresthesia into the upper limb with provocative maneuvers. Use this illustration in gross anatomy and regional anatomy coursework to clarify how the middle scalene relates to the cervical transverse processes, first rib, and neighboring muscle planes, or in anesthesia and pain medicine materials covering interscalene approaches and thoracic outlet anatomy. It also reads well in physiotherapy and sports medicine publications that discuss neck muscle imbalance and first rib mechanics. Anatomical accuracy verified by SciePro's Medical Advisory Board.