Superior Lateral Brachial Cutaneous Nerve, Lateral View

Description

Emerging from the posterior cord of the brachial plexus as a terminal sensory branch of the axillary nerve, the superior lateral brachial cutaneous nerve is traced along the posterior aspect of the surgical neck of the humerus before it wraps laterally to the surface of the shoulder. From this lateral perspective, the nerve lies deep to the posterior deltoid initially, then becomes subcutaneous as it pierces the deep fascia near the posterior border of the deltoid, distributing over the skin of the superior lateral arm. Surrounding landmarks logically visible include the deltoid overlying the glenohumeral region, the long head of triceps descending posteriorly, and the proximal biceps contour anteriorly, with the nerve running in close relationship to the posterior circumflex humeral vessels around the quadrangular space. Orientation is clear: proximal at the shoulder girdle, distal toward the mid humerus, with the nerve’s field on the lateral arm. Axillary nerve injury is often discussed in terms of deltoid weakness, but the sensory deficit over the lateral shoulder, the so-called regimental badge area, is frequently the bedside clue. This view supports teaching the mechanism in anterior shoulder dislocation and fractures at the surgical neck of the humerus, where traction or compression in the quadrangular space can affect both the axillary nerve and its superior lateral brachial cutaneous branch. Small nerve, big clinical implication. It also helps explain why a patient can present with numbness lateral to the deltoid even when motor findings are subtle. Use this illustration for gross anatomy and neuroanatomy teaching on peripheral nerve topography of the shoulder, and for trauma, orthopedics, or sports medicine publications covering axillary neuropathy patterns. It also fits procedural education on safe deltoid intramuscular injection zones and surgical approaches that split or retract the deltoid while preserving cutaneous branches. Anatomical accuracy verified by SciePro's Medical Advisory Board.