PARADOXICAL EMBOLISM AS A CAUSE OF ISCHEMIC STROKE OF UNCERTAIN ETIOLOGY - A TRANSCRANIAL DOPPLER SONOGRAPHIC STUDY

Background and Purpose This study was designed to test the hypothesis that paradoxical embolization would be a cause of embolic strokes and transient ischemic attacks in patients with stroke of uncertain etiolo gy in all age groups. Methods Thirty patients who had stroke of uncert ain etiology were studied. They were divided into the following three groups: 13 patients with sudden onset (group A), 11 patients with suba cute onset (group B), and 6 asymptomatic stroke patients (group C). El even patients with stroke of obvious etiology (group D) and 11 normal healthy volunteers (group E) were also studied as controls. In all pat ients transcranial Doppler sonography and contrast echocardiography we re recorded simultaneously after intravenous injection of the contrast medium. Findings of positive patent foramen ovale in contrast echocar diography or ''chirp'' sounds in transcranial Doppler sonography were defined as positive for paradoxical contrast embolization. Radioisotop e phlebography of the lower extremities and pulmonary scintigraphy, us ing technetium-99 macroaggregated albumin, were performed in all 17 pa tients who had positive findings of paradoxical contrast embolization and in 12 patients whose findings were negative. Results Positive find ings of paradoxical contrast embolization were found in 17 subjects by transcranial Doppler sonography but in only 8 on contrast echocardiog raphy. These positive findings were detected more frequently in group A (77%) than in groups B, D, and E (9%, 18%, and 9%, respectively) (P< .05). In group C, 4 of 6 patients (67%) had positive findings. There w ere positive findings on both phlebography and pulmonary scintigraphy only in 6 group A patients, with positive findings of paradoxical cont rast embolization. Conclusions Transcranial Doppler sonography is a se nsitive detector of right-to-left shunts. Paradoxical cerebral emboliz ation might be frequent in patients with stroke of unknown etiology, e specially when the stroke is of sudden onset.