Fig. 4. Formation, relation to CBM, and branching patterns of the MCN. (A) The MCN is the continuation of the LC of brachial plexus. It pierces CBM and descends between biceps and brachialis muscle. MCN gives branches to biceps (1), brachialis (2) and continues as LCF (3). The MN has three roots, two lateral (R1, R2) originating from its corresponding cord the LC and one MR originating from the MC of brachial plexus. Muscular branch to CBM originating from LC (arrow). (B) The MCN has two roots; one originating from the LC (R1) and the other (R2) originating from MC. MCN pierces CBM and gives branches to biceps (1), brachialis (2) and LCF (3). Also, the MN of this limb has one root only originating from the medial cord and crosses the BA deeply from lateral to medial aspect. (C) The MCN is normally formed as a continuation of the LC and descends superficial to CBM without piercing to pass between biceps and brachialis muscles. MCN gives branches to biceps (1), brachialis (2), and LCF (3). The MN is formed on the medial side of the BA from long LR of LC and MR from MC of brachial plexus. (D) The abnormal formation of MN from MC and union of the anterior division of both UT and MT that form the LC. MN gives branches to CBM (arrow), biceps (1), brachialis (2) and LCF (3). The MN crosses the BA superficially from lateral to medial side to pass deep to the abnormal insertion (****) of the brachialis muscle. MCN is absent. CBM, coracobrachialis muscle; MCN, musculocutaneous nerve; SH, short head of biceps; LH, long head of biceps; BA, brachial artery; AX, axillary artery; LC, lateral cord; MN, median nerve; MR, medial root; MC, medial cord; LCF, lateral cutaneous nerve of forearm; UN, ulnar nerve; LR, lateral root; MC, medial cord; UT, upper trunk; MT, middle trunk; Lat. Dorsi, latissimus dorsi muscle; MCF, medial cutaneous of forearm.
© Anat Cell Biol