The Unilateral and Bilateral Absence of the Musculocutaneous Nerve

The brachial plexus is responsible for the innervation to the upper limb. The musculocutaneous and median nerves are terminal branches off the brachial plexus. The musculocutaneous nerve supplies motor innervation to anterior flexor muscles of the arm. The median nerve provides motor innervation to most flexor muscles of the forearm, pronator muscles of the forearm and passes through the carpal tunnel to innervate certain muscles of the hand. In the absence of the musculocutaneous nerve, the median nerve typically supplies the musculature of the anterior flexor compartment of the arm, including: biceps brachii muscle, brachialis muscle and at times the corocobrachialis muscle. In the case of a high median nerve injury, a variation of an absent musculocutaneous nerve may not only result in typical palsy of the forearm and hand, but also experience palsy in the arm. Therefore, understanding the prevalence and anatomical characteristics of the absence of the musculocutaneous nerve is clinically important. Among 44 brachial plexuses from 22 cadavers assessed, an absent musculocutaneous nerve was observed in 4 plexuses (9.1%) among 3 (13.6%) cadavers. A single female cadaver revealed a bilateral absence of the musculocutaneous nerves in comparison to one female cadaver showing a right unilateral absence of the musculocutaneous nerve and one male demonstrating a left unilateral absence of the musculocutaneous nerve. In all cases, the median nerve supplied both the biceps brachii and brachialis muscles. In summary, a systematic review of the absence of the musculocutaneous nerve demonstrated that females are under‐represented, relative to males and a unilateral absence of the musculocutaneous nerve in a female should be considered a particularly rare finding. Support or Funding Information WV Research Challenge Fund [HEPC.dsr.17.06] This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .