Posterior Perspective of the Superior Trunk of the Brachial Plexus

Description

Posteriorly, the cervical spinal nerves C5 and C6 emerge from the intervertebral foramina and converge lateral to the cervical vertebrae to form the superior trunk of the brachial plexus, rendered as a prominent yellow nerve segment deep to the sternocleidomastoid. From this trunk, the anterior and posterior divisions split as the plexus courses inferolaterally toward the posterior triangle, lying in the expected plane between the anterior and middle scalene muscles. Inferiorly and laterally, the nerve elements track toward the shoulder girdle with the scapulae and proximal humeri providing bony reference points, while the occipital bone and upper cervical spine anchor the superior boundary of the field. Posterior orientation matters when you are teaching how the brachial plexus roots and trunks relate to the cervical transverse processes and the scalene interval, because many learners struggle to translate anterior textbook schematics into the operative and imaging perspectives used in practice. Traction injuries involving C5 to C6 (classically Erb palsy) localize to the superior trunk and often present with weakness of shoulder abduction and external rotation, and this view helps connect that clinical pattern to the anatomy before the plexus reorganizes into cords around the axillary artery. Clear landmarks. The relationship to the sternocleidomastoid and the posterior triangle also aligns with the path of a supraclavicular brachial plexus block and with surgical exposure during exploration after penetrating trauma. Educators can place this plate in gross anatomy and neuroanatomy teaching on brachial plexus formation, in anesthesia materials covering supraclavicular approaches, or in orthopedic and peripheral nerve surgery references discussing C5 to C6 lesions and upper plexus repair. It also fits well in radiology teaching files when correlating plexus levels to cervical spine MRI and CT landmarks. Anatomical accuracy verified by SciePro's Medical Advisory Board.