Neurogenic Thoracic Outlet Syndrome Secondary to Anomalous First Thoracic Rib: A Case Report

Background: Thoracic outlet syndrome (TOS) is an uncommon condition resulting from compression of neurovascular structures at the thoracic outlet.Cervical ribs and fibrous bands are the common etiologies, whereas an anomalous first thoracic rib is extremely rare and only limited case reports have been described.Neurogenic TOS is the most frequent subtype and may mimic other neurological disorders, often delaying diagnosis.Methods: We report the case of an 18-year-old female who presented with progressive pain and paresthesia in the left upper limb.Imaging with CT thorax and three-dimensional reconstruction revealed a hypoplastic anomalous first thoracic rib forming a pseudoarthrosis with the middle third of the second rib, compressing the brachial plexus.Preoperative evaluation also included an MRI, which confirmed the neurogenic component. Results:The patient underwent surgical excision through a supraclavicular approach.The anomalous rib and pseudoarthrosis were carefully removed, decompressing the brachial plexus.Intraoperative pleural injury was promptly repaired.Postoperatively, symptoms improved rapidly, and at one-month follow-up, she had complete resolution with full upper limb mobility.The patient remained symptom-free at one year.Conclusion: An anomalous first thoracic rib is a rare congenital cause of neurogenic TOS.Imaging with CT and MRI plays a crucial role in defining the anomaly and guiding surgical planning.Limited surgical excision via a supraclavicular approach offers adequate exposure and can provide excellent functional recovery with minimal morbidity.