Ansa brachii from a median-musculocutaneous trunk: an anatomical variation - a case report

Anatomical variations in humans are widespread but highly complex. A thorough understanding of anatomy is essential for successful surgical and anesthetic procedures. Brachial plexus anatomical variations are prevalent and account for more than 50% of anatomical variations in cadaveric analyses of the human nervous system. Clinical outcomes may be unsatisfactory if specific brachial plexus anatomical variations are overlooked. In 22% of axillary blocks, the musculocutaneous nerve location was found to be irregular. It may be joined to the median nerve and extended distally before disconnecting from it or may be located close to the axillary artery more frequently. Hence, understanding the anatomy of the brachial plexus is necessary for excellent clinical outcomes in upper extremity surgical procedures. We identified a complex left brachial plexus anatomical variation during the upper limbs dissection course. From the lateral cord, two parallel nervous brands emerge as the musculocutaneous nerve and median nerve fusing into the median-musculocutaneous common trunk. Distally, this trunk forms the ansa brachii that gives the nerve to the biceps brachii muscle, the nerve to the brachialis muscle, and the lateral cutaneous nerve of the forearm. Four branches from the lateral cord, the musculocutaneous nerve, and the median-musculocutaneous trunk sequentially innervated the coracobrachialis muscle. Successful upper extremity surgery and anesthesia need a thorough understanding of the human brachial plexus anatomy and its variations. Additional research and dissections are encouraged to understand human anatomy and its variations.