T. Itoh et al., PARADOXICAL EMBOLISM AS A CAUSE OF ISCHEMIC STROKE OF UNCERTAIN ETIOLOGY - A TRANSCRANIAL DOPPLER SONOGRAPHIC STUDY, Stroke, 25(4), 1994, pp. 771-775
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.