A Bilateral Symmetric Accessory Coracobrachialis Muscle Combined With an Interconnection of the Musculocutaneous Nerve With the Median Nerve.

This report describes a bilateral symmetric accessory coracobrachialis muscle variant coexisting with a unilateral interconnection of the musculocutaneous nerve and the median nerve. An 80-year-old female cadaver was dissected. The bilateral coracobrachialis muscle variant consisted of three heads: two superficial heads and one deep head. One superficial head arose from the tip of the coracoid process, while the other originated from the short head tendon of the biceps brachii. The deep head of the coracobrachialis muscle emerged from the base of the coracoid process. The musculocutaneous nerve bilaterally coursed between the superficial and deep heads. On the right side, the three-headed coracobrachialis muscle coexisted with an ipsilateral interconnection of the musculocutaneous nerve and the median nerve, located at the lower third of the arm. While the presence of a unilateral three-headed coracobrachialis muscle is not rare (with a prevalence range of 0-22.2%), as well as the distal interconnection between the musculocutaneous nerve and the median nerve at the lower third of the arm (with a prevalence range of 1.8-53.6%), the coexistence of the current bilateral three-headed coracobrachialis muscle variant with the distal interconnection of the musculocutaneous and median nerves is quite unusual. A similar report underscores the finding of the bilateral coracobrachialis muscle variant.