Variant median nerve and lateral antebrachial cutaneous nerve associated with anomalous brachial vein : case report

The brachial plexus is formed by the ventral rami of the lower four cervical and first thoracic spinal nerves, with a variable contribution from C4 and T2. All the nerves of the brachial plexus are formed and remain in two planes, anterior and posterior. The anterior plane comprises the branches of the lateral and medial cords of brachial plexus while the posterior plane comprises the branches of posterior cord. The musculocutaneous nerve (C5, C6, C7) arises from the lateral cord of the brachial plexus in the axilla and innervates coracobrachialis, biceps brachii and brachialis muscles. It terminates as the lateral cutaneous nerve of the forearm which supplies the skin of the anterolateral region of forearm as far distally as the base of the thenar eminence. The median nerve will be formed in the axilla by fusion of its medial and lateral roots, derived from the respective cords of the brachial plexus [1]. Variations in the formation of the brachial plexus, as well as the course and distribution of its terminal branches in the upper extremity, have been reported in the literature [2–6]. Such variations may be observed at surgery, autopsy, and cadaveric dissection. Distribution of the median nerve in the arm is not usually subjected to variation [7]. Generally, it does not give any muscular branch in the arm, except for a variable branch to the pronator teres muscle given off proximal to the elbow joint [8]. Some of the reported variations of median nerve include; anomalous formations [2, 9–11], anomalous position [12, 13], loop formation surrounding the median artery [14, 15] and duplication proximal to the carpal tunnel [16]. Variations in the course and distribution of musculocutaneous nerve have been reported previously [5, 17]. It may communicate with the median nerve in the arm [18–25] or be absent [7, 26-28]. Variant anatomy recognized during routine cadaveric dissection has important learning potential, provides a framework to review the embryogenesis of the structure in question, and provides insight into its surgical, medical, and radiologic implications. Moreover, it imparts the concept of patient uniqueness and subsequent individualization of medical and surgical therapies. Although there are reports regarding variations of median nerve and musculocutaneous nerve, anatomic variations involving brachial vein and lateral antebrachial cutaneous nerve (LABCN) are rare. The brachial veins are venae comitantes accompanying the brachial artery and unite with the basilic vein to form the axillary vein.