Superior Lateral Brachial Cutaneous Nerve, Posterior View

Description

Arising from the posterior cord as the cutaneous continuation of the axillary nerve, the superior lateral brachial cutaneous nerve is traced across the posterior shoulder and onto the posterolateral upper arm. Posterior bony landmarks frame its course, including the scapular spine, lateral border of the scapula, proximal humerus, and adjacent posterior ribs with thoracic vertebrae in the midline. The nerve passes inferior to the glenohumeral joint region and then descends superficially over the deltoid insertion area toward the lateral arm, where it supplies skin over the lower deltoid and proximal posterolateral brachium. Fine structural detail can be appreciated along the nerve trunk, including the neurilemma and bundled fasciculi. That relationship to the axillary nerve makes this a practical teaching view for shoulder trauma. Injury at the surgical neck of the humerus or compression within the quadrangular space can interrupt axillary nerve fibers, producing deltoid weakness and a well-localized patch of sensory loss over the lateral shoulder (the classic regimental badge area) carried by the superior lateral brachial cutaneous nerve. Posterior orientation helps clarify why this sensory deficit can persist even when anterior shoulder structures appear intact on gross inspection. A small nerve, but a decisive sign. Course directors in upper-limb anatomy and neuroanatomy can use this plate to anchor dermatomal and peripheral nerve sensory mapping, and to contrast axillary nerve cutaneous territory with the intercostobrachial nerve and posterior cutaneous nerve of arm. It also fits operative and sports medicine materials covering posterior shoulder approaches, deltoid-splitting incisions, and post-injection neuropathy around the deltoid region. Anatomical accuracy verified by SciePro's Medical Advisory Board.