When Pulmonary Embolism Opens the Door: Paradoxical Thalamic Stroke Through a Patent Foramen Ovale

Paradoxical embolism through a patent foramen ovale (PFO) is an uncommon but clinically important cause of acute ischemic stroke, particularly in the setting of pulmonary embolism (PE). We report a 46-year-old man who presented with bilateral grade C3-R (previously sub-massive) PE and subsequently developed focal neurological deficits, including word-finding difficulty. CT pulmonary angiography confirmed the diagnosis of PE, and transthoracic echocardiography with bubble study identified a PFO with right-to-left shunting. Contrast-enhanced brain MRI then demonstrated an acute left thalamic infarct consistent with paradoxical embolic stroke. Alternative etiologies were excluded. Management decisions regarding anticoagulation and PFO closure were made through a structured multidisciplinary process involving the patient. This case draws attention to the need for a high index of suspicion for paradoxical embolism when PE and PFO coexist with new neurological symptoms, and shows how early recognition, timely workup, and patient-centred decision-making together affect clinical outcomes.