Middle Scalene

Description

Positioned deep to the posterior cervical musculature, the middle scalene (scalenus medius) is visualized along the lateral aspect of the cervical spine, arising from the posterior tubercles of the transverse processes of C2 to C7 and descending inferolaterally toward the first rib. Posteriorly, the splenius capitis and splenius cervicis form a more superficial layer, spanning from the nuchal region and upper thoracic spinous processes to the mastoid process and cervical transverse processes, framing the deeper scalene mass. Midline landmarks include the occipital bone and the spinous processes of the seven cervical vertebrae; inferolaterally, the superior angle of the scapula and posterior rib elements cue the transition into the cervicothoracic junction. Depth matters here. Anatomically, scalenus medius defines the posterior boundary of the interscalene triangle, the corridor where the brachial plexus roots and trunks course between the anterior and middle scalenes while the subclavian artery passes inferiorly, a relationship central to both thoracic outlet syndrome and regional anesthesia. Hypertrophy, spasm, or fibrous bands of the scalene muscles can narrow this space and reproduce neurogenic symptoms in the upper limb, while a cervical rib or anomalous first rib further compromises the outlet. For anesthesiologists, the middle scalene serves as a practical landmark during an interscalene brachial plexus block, where needle trajectory and local anesthetic spread must respect the proximity of the plexus and avoid unintended neuraxial or vascular injection. Use this posterior cervical view for teaching layered neck anatomy in gross anatomy and kinesiology courses, for illustrating thoracic outlet compression mechanisms in neurology or vascular surgery texts, or for procedural guidance figures in anesthesia and pain medicine modules. It also reads well in clinical education materials discussing cervical spine trauma and compensatory scalene overactivity after whiplash-associated disorders. Anatomical accuracy verified by SciePro's Medical Advisory Board.