VASCULAR DISTRIBUTION OF PARADOXICAL EMBOLI BY TRANSCRANIAL DOPPLER

Background and purpose. Paradoxical embolism through a patent foramen ovale is a contributory mechanism to stroke and may be diagnosed by contrast echocardiography. The intracranial distribution of these emboli has not been previously reported. Methods. We used transcranial Doppler combined with agitated saline contrast injection to determine whether there was a preferential distribution of the contrast into the anterior or posterior intracranial circulation of patients with an acute stroke or transient ischemic attack. Results. Forty-nine patients were studied-27 men and 22 women, with a mean age of 62.7 +/- 13.3 years (range, 29 to 85 years). Microcavitations were detected in the proximal right middle cerebral artery in 12 of 49 patients (24%). A patent foramen ovale was confirmed in all cases by simultaneous transesophageal echocardiography. Of the 12 patients, microcavitations were also detected in the proximal basilar artery in nine (75%). Conclusions. While paradoxical embolism appears to occur more frequently in the anterior circulation, the high rate of detection of microcavitations in the basilar artery suggests that paradoxical embolism to the posterior intracranial circulation may be more frequent than generally believed.