The anatomy of the extrathoracic intercostobrachial nerve

Background: In the past decade surgeons have become increasingly aware of t he morbidity caused by the division of the intercostobrachial nerve (ICBN) during axillary dissection. To prevent this problem and also to explain its variable occurrence, a detailed knowledge of the anatomy of the nerve is r equired. Methods: Twenty-eight axillary dissections were performed demonstrating the anatomy of the ICBN. Results: in all dissections the nerve originated from the second intercosta l space, with contributions from the first and third intercostal nerve each on one occasion. The posterior axillary branch was constant but may branch early, simulating a second nerve. The ICBN had a Variable relationship to the lateral thoracic vein: anterior, posterior or wrapping around it. In 36 % then was a connection to the medial cord of the brachial plexus in the ax illa. In the upper arm the nerve lies in the subcutaneous fat; in the major ity it supplied at least the proximal half of the arm, and in one-third it reached the level of the elbow joint. In 18% there was a connection to the medial cutaneous nerve of the arm. Conclusion: The ICBN and its main branch (the posterior axillary nerve) wer e constant in all dissections. But its origin, size, connection to the brac hial plexus and medial cutaneous nerve of the arm were variable, as was its ultimate destination in the arm.