Lateral Perspective of the Superior Trunk of the Brachial Plexus

Description

Angling in from the lateral neck and shoulder, the C5 and C6 ventral rami converge to form the superior trunk of the brachial plexus as it emerges between the anterior and middle scalene muscles, superior to the middle trunk (C7) and inferior trunk (C8 to T1). The trunk sits posterior to the clavicle and superior to the first rib, then courses laterally toward the supraclavicular fossa where its anterior and posterior divisions begin to organize. Superficial landmarks include the clavicle and scapula with overlying deltoid and trapezius, framing the plexus as it transitions from cervical to axillary territory. A nearby blue vessel suggests the subclavian to axillary venous pathway, a useful orientation aid in this crowded corridor. Lateral emphasis clarifies the site where traction injuries often concentrate, because the superior trunk is relatively fixed proximally at the scalene interval yet tethered distally as the plexus approaches the clavicle and shoulder girdle. Erb-Duchenne palsy maps directly to this level: weakness of shoulder abduction and lateral rotation, plus elbow flexion, tracks with involvement of C5 to C6 contributions that will feed the suprascapular nerve and the posterior cord via the posterior division. Compression can also occur at the interscalene triangle, and this angle helps you explain why symptoms may worsen with overhead activity or scalene hypertrophy. Small space. Big consequences. Use this artwork for teaching brachial plexus formation in gross anatomy, neuroanatomy, and regional anesthesia modules, especially when introducing interscalene block targets and the relationship of plexus elements to the clavicle and shoulder musculature. It also fits operative atlases discussing supraclavicular exposures or nerve graft planning in upper trunk lesions. Anatomical accuracy verified by SciePro's Medical Advisory Board.