Paradoxical Cerebellar Embolism Associated with Platypnea-orthodeoxia Syndrome

Platypnea-orthodeoxia syndrome is a rare clinical entity characterized by dyspnea and arterial blood deoxygenation in a sitting position. An 89-year-old woman was diagnosed with subacute cerebellar infarction. Her blood oxygen saturation decreased to 88% in a sitting position, resulting in dyspnea. Cardiological thoracic computed tomography revealed an unruptured aortic aneurysm, an enlarged ascending aorta, right atrial compression, and counterclockwise rotation of the heart. An anatomical distortion of the atrial septum induced by these abnormalities directed the atrial venous inflow such that the right-left shunt flow was exacerbated in a sitting position.