Background Subclavian artery stenosis can lead to retrograde flow from an ipsilateral vertebral artery which can result in significant cerebrovascular symptoms (i.e. Vertebral Basilar Insufficiency syndrome, VBI). An Aberrant Right Subclavian Artery (ARSA) is an anatomical variation resulting in the right subclavian artery arising from the aortic arch rather than the right brachiocephalic artery. Our patient presented with both conditions, each exceedingly rare. Case Presentation We present the case of a 76-year-old female with a past medical history significant for bilateral rheumatoid arthritis of the hands, hypothyroidism, and osteoporosis who presented to the emergency department for intermittent dizziness, near syncope, and lightheadedness for 2 days. Notably, the patient reported 3 episodes of incomprehensible speech. Physical exam demonstrated absent radial and ulnar pulses on the right with a systolic blood pressure difference from left to right arm of >60 mmHg. Diagnostic imaging confirmed a completely occluded and calcified ARSA. After a careful multidisciplinary discussion, the diagnosis of an occluded ARSA causing VBI was made. A right subclavian-carotid transposition procedure was performed to restore adequate blood flow and alleviate her symptoms. Her postoperative course was complicated by Horner syndrome.

Discussion While ARSA is often asymptomatic, this patient exhibited symptoms due to the occlusion. Those that are symptomatic most commonly present with dysphagia, dyspnea, and coughing; VBI being exceedingly rare. Since the patient’s right subclavian artery was completely occluded at its origin and proximal segments, the right upper extremity received its blood flow through retrograde flow from the ipsilateral vertebral artery, which resulted in decreased cerebral perfusion without ischemic changes. While endovascular treatment can be considered first line in treating subclavian artery stenosis, the option of a carotid-subclavian bypass or carotid-subclavian transposition are available. Considering the anatomic variation present on this patient, the completion of a subclavian-to-carotid transposition was performed with immediate correction of blood flow. This case highlights the importance of recognizing rare vascular anomalies and unique pathophysiological presentations and the need for tailored surgical approaches in complex presentations.