Triple Independent Segmental Drainage of the Brachial Veins Into the Basilic Vein Associated With Variant Formation of the Median Nerve: A Cadaveric Case Report.

Variations of the upper-limb venous system are relatively common; however, complex segmental venous drainage patterns associated with neural variations remain exceptionally rare. Detailed knowledge of these anatomical configurations is clinically important because the basilic and brachial veins are frequently involved in vascular access procedures, venous catheterization, reconstructive microsurgery, and axillary surgery. The present cadaveric case report describes a rare neurovascular variation identified during routine educational dissection of the left upper limb of a 75-year-old male donor. The variation consisted of triple independent segmental drainage of the brachial veins into the basilic vein, resulting in a non-classical multilevel formation of the axillary vein. The first brachial vein drained into the basilic vein at the middle third of the arm, the second near the origin of the ulnar nerve, and the third near the formation of the median nerve. Additionally, the median nerve demonstrated a variant formation consisting of two lateral roots and one medial root. Of particular anatomical and clinical significance, the third brachial vein coursed anterior to the medial root of the median nerve before draining into the basilic vein. The coexistence of multiple venous and neural variations resulted in a complex neurovascular arrangement in the axillary region. Such anatomy may increase the risk of hemorrhagic or neural complications during venous catheterization, brachiobasilic arteriovenous fistula creation, axillary lymph node dissection, brachial plexus exploration, and reconstructive vascular procedures. Particular caution may be warranted during ultrasound-guided venous cannulation, peripherally inserted central catheter placement, and brachiobasilic fistula transposition. The present case highlights the importance of recognizing rare combined neurovascular variations and performing careful preoperative vascular mapping to minimize complications during upper-limb surgical and interventional procedures.