The variable communicating branches between musculocutaneous and median nerves: a morphological study with clinical implications.

BACKGROUND: The course of the brachial plexus, its relations with surrounding structures and unique primary and secondary divisions result in its wide range of anatomical variations. Most of these variations were detected during anatomical dissections and studies. It has been found that 53% of studied brachial plexuses contained variations. The communication between musculocutaneous and median nerves is the most common variation of infraclavicular part of brachial plexus.

METHODS: During gross anatomical dissections of peripheral nerves, we observed neuronatomical variations in upper limbs of four formalin embalmed adult cadavers. Musculocutaneous and median nerves were connected by a communicating branch at distinct level in each cadaver. The formation and relations of both nerves were noted in each case to exclude the existence of other anatomical variations. The connections were measured and documented by digital camera.

RESULTS: The communicating fibers of variations 1 and 2 were located in the upper third of arm and proximally to musculocutaneous nerve penetration through coracobrachialis muscle. In variations 3 and 4, the communicating branch was situated in the lower third of arm and distal to the nerve penetration point.

CONCLUSION: Variable interconnections between musculocutaneous and median nerve have to be considered in diagnosis of nerve lesions in axillary and arm regions. Compound musculocutaneous and median nerve neuropathy would occur in lesions of the interconnecting branches. Injuries of musculocutaneous nerve proximal to these branches can cause particular and unexpected symptoms, such as weakness of forearm flexors and thenar muscles (Fig. 6, Ref. 28).