Silent cerebral infarcts in patients with pulmonary embolism and a patent foramen ovale: a prospective diffusion-weighted MRI study.

BACKGROUND AND PURPOSE: Pulmonary embolism is thought to be associated with a small but definite risk of paradoxical embolism in patients with a patent foramen ovale (PFO). Although neurological complications are infrequent, the incidence of clinically silent brain infarction is unknown. We assessed the rate of clinically apparent and silent cerebral embolism in patients with pulmonary embolism in relation to the presence or not of a PFO. METHODS: We used diffusion-weighted MRI in patients hospitalized for a pulmonary embolism to assess cerebral embolic events. Sixty consecutive patients were evaluated at diffusion-weighted MRI. All patients underwent neurological assessment before diffusion-weighted MRI and a contrast echocardiography to detect PFO the next day. RESULTS: Diffusion-weighted MRI showed bright lesions in 6 patients among the 60 consecutive patients with pulmonary embolism in a pattern consistent with embolic events. There was only one patient with a neurological deficit. After contrast echocardiography, a PFO was diagnosed in 15 patients (25%). The frequency of silent brain infarcts in patients with a PFO was significantly higher than in patients without PFO (5 [33.3%] of 15 versus one [2.2%] of 45 patients, P=0.003). By logistic regression analysis, PFO was identified as an independent predictor of silent brain infarcts (OR, 34.9 [3.1 to 394.3]; P=0.004). CONCLUSIONS: In pulmonary embolism, cerebral embolic events are more frequent than the apparent neurological complication rate. The prevalence of silent brain infarcts is closely related to the presence of a PFO suggesting a high incidence of unsuspected paradoxical emboli in those patients.