Transcranial Doppler ultrasonography (TCD) is the real-time non-invasive neuroimaging modality, which has been rapidly evolving from a simple diagnostic tool to a broad spectrum of clinical applications. TCD performed in acute stroke may provide informations about prognosis. Occlusion of middle cerebral artery (MCA) is associated with 2-fold increased risk of death, while patent MCA with 10-fold chance of early clinical improvement. Full recanalization (<6 hours) may predict 5-fold increased chance of early clinical improvement and functional independence. No residual flow on pretreatment TCD has less probability of complete recanalization and poor long-term outcome in spite of intravenous thrombolysis, hence early decision for combined endovascular rescue may be considered. Flow diversion in acute MCA occlusion is well correlated with leptomeningeal collaterals on angiography. Cerebral steal phenomenon, demonstrated by breath-holding method, is present in 14% of acute stroke or transient ischemic attack and neurological deterioration is present in half. Patients with persisting arterial occlusion or excessive sleepiness are particularly vulnerable. Sonothrombolysis with lipid-coated perflutren microsphere is promising. Sonothrombolysis with microsphere showed a trend toward higher early recanalization and clinical recovery compared to standard tPA therapy. However, concerns about symptomatic hemorrhage remain in higher-dose tier. Clinical-Sonograpic Index (CSI), determined by flow velocity, asymmetry index, difference of pulsatility index, presence of corresponding symptoms or diabetes, enhances diagnostic accuracy for MCA stenosis. Contrast TCD is a sensitive method for the detection of patent foramen ovale (PFO) (sensitivity 97%, specificity 78%), and combination of contrast TCD and contrast TEE is suggested as the gold standard for the diagnosis of PFO. Journal of Neurosonology 1(1):24-28, 2009

Key Words: Transcranial Doppler sonography, Acute stroke, Recanalization, Sonothrombolysis, Middle cerebral artery stenosis, Patent foramen ovale