A rare bilateral absence of the musculocutaneous nerve associated with muscular and vascular variations: embryological considerations and clinical implications

Introduction: Muscular, nervous, and vascular variations in the anterior compartment of the arm are common if considered independently. However, the co-existence of variations involving all the anterior compartment of the arm structures is very rare. This case report aims to report a rare bilateral presentation of the muscular, nervous, and vascular variations in the anterior compartment of the arm. Case presentation: An incidental finding during the routine dissections of the anterior compartments of the arm, elbow joint and forearm is presented. The musculocutaneous nerve was absent bilaterally. The coracobrachialis originated from the coracoid process of the scapula and the anterior aspect of the shoulder joint capsule bilaterally and was innervated by a direct branch from the lateral cord of the brachial plexus. The third head of the biceps brachii was also present bilaterally. The brachialis muscle presented with two heads with dual innervation by the median and radial nerves and dual blood supply by brachial-ulnar and profunda brachii arteries. There was a bilateral high bifurcation of the brachial artery. Conclusion: This case shows that anatomical variation of all the structures in the anterior compartment of the arm can exist at the same time bilaterally. This knowledge may be important clinically to avoid misdiagnosis and iatrogenic injuries to the anterior compartment of the arm due to the altered conventional anatomy.