Middle Scalene, Lateral View

Description

Positioned on the lateral neck, the middle scalene (musculus scalenus medius) is highlighted along the posterolateral border of the cervical region, lying posterior to the anterior scalene and deep to the sternocleidomastoid. Its muscular slips descend from the transverse processes of the mid cervical vertebrae to the superior surface of the first rib, placing it superior to the clavicle and medial to the shoulder girdle. Adjacent bony landmarks include the mandible and zygomatic arch superiorly, the cervical vertebral column posteriorly, and the upper thoracic cage inferiorly. The muscle’s inferior attachment aligns near the scalene tubercle region of rib 1, where key neurovascular structures pass nearby. A lateral emphasis on scalenus medius matters because it frames the interscalene interval, the corridor used to localize the roots and trunks of the brachial plexus for regional anesthesia. This is the anatomy behind interscalene blocks and also the anatomy behind their complications, including phrenic nerve palsy and inadvertent neuraxial spread when needle trajectory drifts medially. Hypertrophy, spasm, or fibrous bands of the scalene group can contribute to neurogenic thoracic outlet syndrome, where symptoms follow a lower plexus distribution and are often provoked by arm elevation. Small muscle, big consequences. Use this asset in gross anatomy teaching of the lateral cervical region, in anesthesia texts and lectures covering the interscalene approach, or in clinical education materials on thoracic outlet syndrome and cervical rib variants. It also fits well in surgical orientation content where the first rib, clavicle, and scalene attachments guide supraclavicular exposure. Anatomical accuracy verified by SciePro's Medical Advisory Board.