A Rare Case of Atypical Formation of Musculocutaneous Nerve not Perforating Coracobrachialis Muscle: Embryological and Clinical Implications

Abstract

An rare anomaly of the musculocutaneous nerve was detected during routine dissection of the left upper limb of a 42-year-old Turkish male cadaver. Musculocutaneous nerve extend in a common cover together with the lateral cord and lateral root of median nerve without separating from the lateral cord. The lateral and medial roots deriving from their corresponding cords combined ventral to the axillary artery forming a true common trunk of the musculocutaneous nerve and median nerve. The musculocutaneous nerve branched off from the median nerve 0.5 cm distal to the junction of the lateral and medial roots of median nerve. The musculocutaneous nerve traveled between the biceps brachii and coracobrachialis muscles without piercing the coracobrachialis muscle and crossed over the axillary artery. After passing between the biceps brachii and brachialis muscles, the musculocutaneous nerve continued as the lateral cutaneous nerve of the forearm. There was no prominent musculocutaneous nerve branch observed to innervate the coracobrachialis muscle. Very thin nerve branches were observed extending from the lateral cord and musculocutaneous nerve to the  oracobrachialis muscle. A connection extending from the proximal part of the lateral cord to the point where the ulnar nerve originated in the distal part of the medial cord was also detected. Knowledge of upper extremity anatomical variations helps surgeons during surgical interventions and treatments to avoid potential iatrogenic injuries during surgery.