SummaryCryptogenic, or unexplained, stroke is present in about 30%-40% of ischemic stroke patients. Pursuing a stroke mechanism is important in such patients to better choose therapy to reduce the stroke recurrence risk. Intracranial vessel imaging and cardiac evaluation with transesophageal echocardiogram and outpatient cardiac monitoring may help identify the stroke mechanism. This article highlights the diagnostic yield of various tests in identifying a stroke mechanism in stroke patients whose initial diagnostic evaluation is negative, and the implications for treatment.A 57-year-old man with an unremarkable medical history presented to the emergency room 5 days after the acute onset of left arm and hand weakness and numbness. He denied other neurologic symptoms. Blood pressure was 160/78 mm Hg and heart rate 78 and regular. General physical examination results were normal. He had mild dysarthria. Mental status and cranial nerve examination results were otherwise normal. He had mild weakness and reduced dexterity in the left hand, but cerebellar and sensory examinations, including graphesthesia and stereognosis, had normal results. ECG showed normal sinus rhythm. MRI showed a small cortical infarct in the right precentral gyrus (figure 1). Magnetic resonance angiography showed no major carotid or intracranial arterial stenosis. Inpatient telemetry did not show atrial fibrillation. Transthoracic echocardiography with agitated saline contrast suggested an intracardiac shunt, and transesophageal echocardiography confirmed the diagnosis of a patent foramen ovale (PFO) associated with an atrial septal aneurysm. A subsequent 21-day outpatient cardiac monitor did not show evidence of atrial fibrillation. He was treated with antiplatelet and statin therapy and referred for evaluation for participation in a randomized trial of interventional closure for PFO.
BACKGROUNDIdentifying the stroke mechanism is a crucial aspect of secondary prevention of ischemic stroke. However, no stroke etiology is identified in 30%-40% of patients.1,2 Cryptogenic stroke is the term used to refer to strokes for which no definite cause can be identified.