Variation in the Distribution of Nerves in the Front of Arm- A Cadaveric Study from South India

Abstract

Introduction: Brachial plexus are the main nerve supply to the muscles of upper limb and the muscles of the flexor compartment arm are supplied by Musculocutaneous Nerve (McN). Any variations in the nerve innervation of the flexor muscles of arm should be documented as they have clinical implications. Aim: To observe and document the variations in the innervation of muscles of the front of arm and discuss its clinical implications with the help of available literature. Materials and Methods: This cross-sectional descriptive study was done in the Department of Anatomy, Siddhartha Medical College for a period of three years that is from October 2017 to October 2020 on 50 upper limbs, from 25 cadavers. The upper limbs were dissected to observe the innervations of muscles of front of arm. Contents of front of arm were observed. Incidence and percentage of variation in the population was tabulated. Results: Variations in the nerve supply of muscles of front of arm were noticed in 6% of the cases. In two cadavers (4%), all the muscles of right arm except coracobrachialis were innervated by a trifurcated branch from Median Nerve (MN) and the latter was supplied by a separate branch from lateral cord. In another left upper limb two separate branches innervated from lateral cord and supplied all the muscles of arm. In the present study, observed variations were more common on right side than on the left side. Conclusion: Knowledge of such variations are important for the surgeons during surgical exploration of axilla, nerve block in supraclavicular, infraclavicular or axillary region and also during nerve grafting. Also, the study highlights the incidence of variations in a particular region.