Inferior Trunk of the Brachial Plexus, Anterior View

Description

Emerging from the lower cervical and upper thoracic spinal nerves, the C8 and T1 roots converge anterior to the scalene musculature to form the inferior trunk of the brachial plexus, shown in relation to the cervical vertebrae, clavicles, and first ribs. From this anterior perspective, the trunk sits inferior to the middle trunk and courses laterally toward the costoclavicular space, where it will divide into anterior and posterior divisions. Proximal-to-distal continuity into the divisions and early cord formation is emphasized against the bony landmarks of the thoracic inlet. Orientation is clean. Clinically, the inferior trunk is the segment most classically implicated in lower plexus patterns such as Klumpke palsy, where traction on the abducted arm preferentially injures C8 to T1 fibers and produces intrinsic hand weakness and sensory loss along the medial forearm and ulnar hand. This same anatomic corridor matters in thoracic outlet syndrome: compression at the interscalene triangle or, more often for the lower plexus, beneath the clavicle at the costoclavicular interval can reproduce paresthesias in the T1 distribution and worsen with shoulder depression. Understanding where the inferior trunk lies relative to the first rib and clavicle also informs regional anesthesia, since targeting the plexus more distally at the supraclavicular level can increase pneumothorax risk because of pleural proximity. Use this artwork for teaching brachial plexus organization (roots, trunks, divisions, cords) in gross anatomy, neuroanatomy, and anesthesia blocks courses, and for illustrating lower brachial plexopathy in neurology, orthopedics, and physical medicine publications. It also suits patient education graphics explaining traction injuries and thoracic outlet compression patterns. Anatomical accuracy verified by SciePro's Medical Advisory Board.