Variation in the method of innervation of the brachialis muscle of the arm with special reference to accessory branches from the musculocutaneous nerve and the median nerve

ABSTRACT

To report a variation in the innervation of the brachialis muscle along with the anomalous communication of the musculocutaneous nerve [MCN] with the median nerve [MN] in the left upper limb of formalin fixed adult male cadaver. During the educational gross anatomy dissections of the left brachium of a formalin fixed cadaver in our laboratory, we encountered a neuro-anatomical variation. The limb was carefully dissected and examined for any further anatomical variations. The accessory branch of the musculocutaneous nerve and the median nerve originated approximately at the midpoint level of the brachial region. The nerves then coursed inferiorly between the biceps and brachialis muscles and communicated with each other forming a plexus. Two separate branches from the plexus innervated the brachialis muscle. However, the brachialis muscle received and additional radix from the accessory branch of median nerve. Another unusual radix was seen arising from the nerve plexus, had a very oblique course and merged with the musculocutaneous nerve to form the lateral cutaneous nerve of the forearm. The knowledge of the communicating branches between the median nerve and the musculocutaneous nerves is important as these communicating branches are more liable to be injured during surgical and clinical investigations