Abnormal Innervation of the Arm Muscles by the Median Nerve: A Case Report

Introduction: Brachial plexus variations have been observed in some people. The median nerve is one of the branches of this plexus, formed by the union of the medial and lateral cords. The median nerve usually does not have a branch in the arm region and innervates the forearm and hand muscles. Case Presentation: During the dissection of the right axillary cavity of a 74-year-old male donor for medical students, the variation in the innervation of arm muscles was observed. Unexpectedly, the biceps brachii and brachialis muscles were innervated by the branches of the median nerve. The median nerve normally does not have a branch in the arm region and innervates the forearm and hand muscles. The musculocutaneous nerve (C5-7) is a terminal branch of the lateral cord and innervates the three muscles of the anterior compartment of the arm, namely coracobrachialis, biceps brachii, and brachialis muscles. Conclusions: The innervation of the arm's anterior compartment muscles by the median nerve is a rare variation that has never been seen in this country. Awareness of such anatomical variations is necessary for physicians and clinicians. These variations should be taken into consideration during axillary region surgeries.