Intercostobrachial Nerve from a Posterior Position

Description

Emerging from the lateral thoracic wall, the intercostobrachial nerve (classically the lateral cutaneous branch of the second intercostal nerve, T2) is shown coursing from the intercostal space, crossing superficial to the serratus anterior and slipping into the axilla toward the medial aspect of the proximal arm. Posteriorly, the scapula and proximal humerus frame the axillary region, with adjacent ribs and thoracic vertebrae providing clear segmental context. Branches of the brachial plexus occupy the posterior shoulder and axilla as parallel yellow nerve pathways, allowing direct comparison between a thoracic intercostal nerve contribution and plexal cords and terminal branches. Posterior orientation matters here because it clarifies how a T2-derived sensory nerve can be encountered during axillary dissection or posterior axillary fold exposure, where it runs close to lymphatic tissue and can be mistaken for a small plexal branch. Sensory loss or dysesthesia along the axilla and medial upper arm after axillary lymph node dissection, mastectomy, or sentinel node biopsy often reflects intercostobrachial nerve injury. A frequent teaching point is its communication with the medial cutaneous nerve of arm and the resulting symptom overlap with lower brachial plexus or ulnar distribution complaints. This is a common exam trap. Use this artwork in gross anatomy and neuroanatomy teaching when distinguishing intercostal nerve branches from brachial plexus structures, and in surgical education materials covering axillary approaches, breast surgery, and lymph node staging. It also fits patient-facing counseling graphics for postoperative numbness patterns after breast and axillary procedures. Anatomical accuracy verified by SciePro's Medical Advisory Board.