Unilateral Subclavian Vein Fenestration Featuring a Traversing Brachial Plexus Nerve Branch and Associated Vascular Dysgeneses in a Female Body Donor

Background: Clinical-surgical procedures in the thoracic outlet can be challenging due to the proximity of neurovascular structures to the subclavian vein. Methods: During a routine anatomical dissection in an undergraduate medical study at Paracelsus Medical University, Nuremberg, a novel anatomical finding was observed in an ethanol–glycerin embalmed, 79-year-old female body. In addition to the standard measurements, hematoxylin eosin staining of relevant vessels was performed Results: A nerve branch separating from the brachial plexus at the C6 spinal nerve traversed inferiorly and passed through a fenestration of the subclavian vein in the lateral section, rejoining the lateral cord of the brachial plexus. In addition, hypoplasia of the right-sided internal carotid artery (ICA) and a left-sided internal jugular vein (IJV) hypoplasia were detected. At the left venous angle of the left IJV, a venous saccular aneurysm was found. The ectopic origin of the left ascending pharyngeal artery originated from the initial segment of the left ICA. Also, Langer’s axillary arches were observed bilaterally in the same subject. Conclusions: The anatomical findings in the specimen do not provide a direct symptomatic correlation or functional relevance comparable to clinical observations. Nevertheless, it is important to highlight this discovery as a potential clinical reference for future studies.