Nonatherosclerotic Subclavian Steal Syndrome Due to Brachiocephalic Trunk Kinking in an Elderly Woman: A Case Report.

BACKGROUND Subclavian steal syndrome (SSS) is typically caused by atherosclerotic occlusion of the proximal subclavian artery. While atherosclerosis is the primary etiology, clinical awareness of non-atherosclerotic triggers is essential for accurate diagnosis. Non-atherosclerotic causes, such as arterial kinking, are exceedingly rare and are frequently overlooked in the differential diagnosis of vertebrobasilar insufficiency. This report describes a case of partial SSS secondary to mechanical kinking of the brachiocephalic trunk (BCT) in an elderly patient, emphasizing the need to consider anatomical variations even without obstructive plaques. CASE REPORT A 66-year-old woman with a history of stroke and atrial fibrillation (CHA₂DS₂-VASc score of 5) was referred for color Doppler ultrasound of the carotid and vertebral arteries. Imaging revealed Stage II (intermittent) flow reversal in the right vertebral artery, characterized by a distinctive mid-systolic deceleration pattern. Subsequent computed tomography angiography (CTA) excluded atherosclerotic disease but demonstrated a severe 90-degree angulation (kinking) at the BCT origin. This anatomical variation created a pressure gradient sufficient to induce a partial steal phenomenon. Given the patient's high thromboembolic risk and clinical stability, a conservative management approach with optimized anticoagulation and strict cardiovascular risk control was prioritized. CONCLUSIONS BCT kinking should be considered a potential hemodynamic cause of SSS when atherosclerosis is absent. This case highlights the importance of multi-modal imaging (color Doppler ultrasound and CTA) in identifying rare anatomical triggers for flow inversion. A conservative strategy is safe when flow in the basilar artery remains stable.