Intercostobrachial Nerve, Anterior View

Description

Arising from the lateral cutaneous branch of the second intercostal nerve (T2), the intercostobrachial nerve courses anteriorly and laterally from the thoracic wall, perforating the intercostal musculature near the midaxillary line before crossing the axilla toward the medial upper arm. From this anterior perspective, the rib cage provides the osseous framework behind the nerve’s thoracic origin, while the shoulder girdle is defined by the scapula and proximal humerus at the glenohumeral joint. The intercostobrachial nerve lies superficial in the axillary fat plane relative to the ribs and intercostal spaces, then travels distally to supply cutaneous sensation over the axilla and the medial aspect of the upper arm. A small but stubborn nerve. Clinically, this is the sensory pathway frequently disrupted during axillary lymph node dissection or sentinel node biopsy in breast and melanoma surgery, and injury classically produces numbness, dysesthesia, or neuropathic pain along the medial brachium. Its relationship to the brachial plexus is a common source of confusion, since it is not a brachial plexus branch, yet it communicates variably with the medial cutaneous nerve of arm and the intercostal nerves, and it becomes a practical landmark when teaching the difference between thoracic wall innervation and true plexus-derived peripheral nerves. This anterior approach also aligns with the surgeon’s view when elevating the skin flaps and identifying superficial axillary neurovascular structures. Use this illustration in gross anatomy and regional anatomy teaching for the axilla, in surgical oncology or breast surgery training materials addressing postoperative sensory deficits, and in patient education graphics explaining medial arm numbness after axillary procedures. It also suits exam stems and review chapters that contrast intercostal nerves with brachial plexus anatomy in the male upper torso. Anatomical accuracy verified by SciePro's Medical Advisory Board.