Abstract
Thoracic outlet syndrome (TOS) is a constellation of symptoms that occur due to the compression of neurovascular structures traversing the thoracic outlet. TOS manifests in 3 distinct forms: neurogenic, venous, and arterial. Among these, arterial TOS is the rarest. A 32-year-old man presenting with severe right arm pain was referred for CT angiography. The imaging revealed bilateral cervical ribs, with the right side showing more pronounced development and fusion with the first thoracic rib. At the fusion site of the right cervical rib and the first thoracic rib, a pseudoaneurysm of the right subclavian artery was detected. Additionally, there was evidence of acute thromboembolism in the right brachial artery at the mid-humerus. Arterial thoracic outlet syndrome is a rare form of TOS that can have detrimental consequences due to associated complications. Cross-sectional imaging, such as CT scans and MRI, is the preferred method for diagnosing TOS and identifying its specific form. Physicians are expected to be familiar with the various forms of TOS, the lesions mimicking TOS, and the imaging tools utilized for diagnosis.