The lateral cord of the brachial plexus piercing the coracobrachialis muscle: A case report

Abstract

Background : The present of variation of brachial plexus is founded in all level of unite of anterior rami of C₅-T₁ spinal nerves. On reviewing literatures reveal that, there are a lot of papers that report in brachial plexus variation ¹.  However the variation of brachial plexus in infraclavicular part with the lateral cord piercing into coracobrachialis muscle is a very rare case ². This variation should be kept in consideration while performing surgical exploration of the axilla and arm regions to avoid damage to these nerves. Objectives : 1.    To study the position and course   of   the lateral cord of brachial plexus that piercing into coracobrachialis muscle. 2.    To study the distribution of the lateral cord of brachial plexus after piercing into coracobrachialis muscle.

Result : Dissection of the left axilla region of the embalmed male cadaver with age 43 years old revealed that the lateral cord of the brachial plexus piercing into coracobrachialis muscle.  On the way within the coracobrachialis, the lateral cord gives off the branch to innervate this muscle and separates to the lateral root of the median nerve and the musculocutaneous nerve.  After passing through the coracobrachialis muscle the musculocutaneous nerve gives off  a branch to innervate this muscle and continuing downward in the interval between the biceps brachii and brachialis muscles and gives off  branches to innervate these muscles. Later the musculocutaneous pierces the brachial fascia above the elbow lateral to the tendon of  biceps brachii muscle and continues as the lateral cutaneous of forearm.

Conclusion :  This report is an anatomical evidence of the variation of lateral cord of the brachial plexus  piercing the coracobrachialis muscle. This variation is suggested to derive since embryonic period, which abnormality of signaling system that control the relation of the differentiation between the muscular and the nervous systems.