Middle Trunk of the Brachial Plexus

Description

Arising from the ventral ramus of C7, the middle trunk of the brachial plexus sits in the posterior cervical triangle between the superior trunk (C5 to C6) superiorly and the inferior trunk (C8 to T1) inferiorly, then courses inferolaterally toward the supraclavicular fossa. Anterior and middle scalene muscles flank the roots and trunks, with the trunks emerging lateral to the scalene interval before passing posterior to the clavicle toward the axilla. The clavicle, superior ribs, and the scapular region form the bony backdrop, while subclavian and proximal axillary vessels run in close proximity to the neural elements along the thoracic outlet. Small branches and early divisions can be appreciated as the neural bundle thickens and reorganizes. For teaching and clinical correlation, the middle trunk matters because it represents the C7 contribution to multiple terminal nerves, so lesions here tend to produce a characteristic pattern of weakness and sensory change that does not respect a single peripheral nerve distribution. Think traction injury with lateral neck bending or shoulder depression, or iatrogenic vulnerability during supraclavicular brachial plexus block when the needle trajectory approaches the plexus lateral to the subclavian artery. This is where topography counts. Use this illustration in gross anatomy and neuroanatomy curricula to anchor trunk level organization, or in anesthesiology and peripheral nerve surgery materials to explain supraclavicular approaches, thoracic outlet relationships, and mechanisms of brachial plexopathy. It also suits textbooks and patient-facing diagrams that need a clean separation of superior, middle, and inferior trunks without losing the muscular and vascular context of the neck, shoulder, and upper chest. Anatomical accuracy verified by SciePro's Medical Advisory Board.