Abstract: Objective  To investigate the transcranial Doppler(TCD) for detection of patent foramen ovale(PFO) in young and middleaged patients with cryptogenic ischemic stroke(CS) and the mechanism of stroke. Methods   The subjects were divided into two groups: CS patient group 70 young and middleaged patients with CS; normol control group 70 healthy persons with matched age and sex for CS group. PFO and the extent of righttoleft shunt(RLS) were  detected by TCD with bubble study and under Valsava maneuver(VM). The atrial septal aneurysm(ASA) was detected by transthoracic echocardiography(TTE) and the deep venous thrombosis(DVT) was detected by color Doppler flow imaging(CDFI). The fibrinogen and platelet aggregation were tested by cluse assay and turbidimetry assay.Results   The prevalence of PFO. PFO with ASA， PFO with DVT and the extent of RLS were significantly higher in CS group than those in normal control group (P<0.01). Compared with normal control group，  the fibrinogen and the frequencies of platelet aggregation in CS group significantly increased(P<0.01). Conclusion  TCD is an excellent method for PFO identification with high sensibility with contrastenhanced and under VM in young and middleaged patients with CS. The mechanism of  PFO induce ischemic stroke may relate to formed of paradoxical embolism.

Key words: ultrasongraphy, doppler, transcranial, foramon ovale, patent, stroke, embolism