Supernumerary Head of the Biceps Brachii Muscle: An Anatomic Variant With Clinical Implications.

ObjectiveThe purpose of this anatomic case report is to describe a variation of the biceps brachii muscle identified in an adult male cadaveric specimen and its potential clinical relevance.MethodsA cadaveric specimen with a left supernumerary biceps brachii muscle was dissected. Adjacent neurovascular structures were isolated, and their pathways were observed for possible areas of compression.ResultsA tricipital supernumerary head of the biceps brachii muscle was noted on the left upper extremity in an embalmed human cadaveric specimen. The median nerve and brachial artery maintained their common neurovascular path. The musculocutaneous nerve passed deep to the third head of the anatomic variant before distributing its cutaneous branches as the lateral antebrachial cutaneous nerve.ConclusionThe presence of a supernumerary biceps brachii muscle may cause neurovascular compression of the median nerve, musculocutaneous nerve, or brachial artery, resulting in peripheral nerve deficits. When patient conditions are refractory to care, they may warrant careful evaluation of the anterior compartment of the arm for potential anomalous muscle variations.