Repair of left brachial artery aneurysm with excision and interposition grafting: a case report.

True brachial artery aneurysms are uncommon and most commonly associated with trauma or connective tissue disorders, with thromboembolism. We report a 41-year-old male with myoclonus dystonia presenting with a 4-week history of an enlarging left arm mass. Imaging revealed a 1.3 cm saccular brachial artery aneurysm, likely due to repetitive blunt trauma. The patient underwent successful excision with reversed basilic vein interposition grafting and was discharged without complications. This case highlights the role of repetitive minor trauma in aneurysm formation and the importance of early surgical management to prevent ischemic complications.