Bilateral Persistent Median Artery and Bifid Median Nerve in a Male Cadaver: An Anatomical Case Report

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Co-authors:

Aditi Mahajan - Georgetown University School of Medicine; Eric Wan - Georgetown University School of Medicine; A Lee Dellon - Departments of Plastic Surgery and Neurosurgery - The Johns Hopkins University School of Medicine; Caitlin Coker - Georgetown University School of Medicine

Abstract Body : During embryonic development, the median artery plays a critical role in the upper limb arterial system and typically regresses during week 8 of gestation with the formation of the radial and ulnar arteries. However, it may persist into adulthood in some cases, leading to the condition known as Persistent Median Artery (PMA). Variations in the median nerve may coexist, such as the division of the median nerve into two distinct branches, typically proximal to the carpal tunnel. This phenomenon is known as Bifid Median Nerve (BMN). This report aims to document a cadaveric case of bilateral PMA and BMN and its anatomical characteristics, shedding light on the clinical implications of this neurovascular variation. During a routine upper limb dissection of a formalin-fixed anatomical donor, a unique bilateral neurovasculature variation was observed. The donor was an 89-year-old Caucasian male with prostate cancer listed as the cause of death. Careful dissection was performed, and anatomical variations were photographed. Bilaterally, the PMA originated from the common interosseous artery, traveled distally through the anterior forearm and carpal tunnel, and terminated in the hand. Proximally, near the origin of the PMA, it penetrated branches of the anterior interosseous nerve and then traveled superficially to pierce the median nerve. The PMA traveled anterior to the median nerve down the distal two-thirds of the forearm, traversing the space between the flexor digitorum superficialis and the flexor digitorum profundus muscles. Proximal to the carpal tunnel, the median nerve bifurcated into medial and lateral branches. The PMA traveled between the branches of the BMN through the carpal tunnel and into the hand. The PMA coursed radially in the hand, aligned with the lateral branch of the median nerve, which innervated digits 1, 2, and the lateral half of digit 3. This variation gave rise to an incomplete superficial palmar arch configuration, as there was no connection between the regions supplied by the median and ulnar arteries in the hand. The presence of a PMA, which may not always be evident since many patients are asymptomatic, has been linked to clinical consequences related to Carpal Tunnel Syndrome (CTS). PMA can compress the median nerve, contributing to CTS. BMN, which occurs 50% more frequently in CTS patients, exacerbates compression due to its larger cross-sectional area. The coexistence of BMN and PMA is variable, emphasizing the need for consideration during anatomical dissection or radiographic assessment. Surgical planning, especially for minimally invasive hand procedures, should include ultrasound assessment to account for PMA configurations and concurrent BMN to prevent complications.