Detecting cerebral microemboli with transcranial doppler.

 

David W. Newell, MDCerebrovascular Surgery, Neurosurgery, Swedish Neuroscience Institute 

 

 

 

 

Colleen Douville, RVT, Director, Cerebrovascular Ultrasound, Swedish Neuroscience Institute

 

 

Since its introduction in 1982, transcranial doppler ultrasound (TCD) has evolved into a por­table, multimodality, noninvasive method for real-time imaging of intracranial vasculature.

The detection of cerebral microemboli is among the more remarkable capabilities of TCD. Emboli create countable signals in the ultrasound display due to the higher reflection of sound waves compared to the blood cells. Experimental mod­els have shown a high sensitivity and specificity for detection of a variety of substrates, including thrombotic, platelet and atheromatous emboli.

Microembolic signals (MES) within the in­tracranial vasculature are most frequently identi­fied in patients with large-vessel atherosclerotic disease, such as carotid stenosis. They have also been reported in intracranial arterial stenosis, ar­terial dissection, cardiac disease and atheroaortic plaque. Additionally, they have been seen in arter­ies distal to coiled aneurysms.

There is strong evidence that MES detection predicts future ipsilateral stroke risk in patients with symptomatic carotid stenosis (Markus HS, et al.; King A, et al.). A recent study of patients with asymptomatic carotid stenosis demonstrated that MES predicted subsequent ipsilateral stroke and TIA, and also ipsilateral stroke alone, and that it is helpful in selecting patients who will benefit from carotid endarterectomy (Markus, HS et al.).

Identification of active embolization provides crucial patho­physiological information to the neurologist and can also aid in the selection of tailored therapy aimed at reducing the risk of stroke. Emboli from different sources have unique compositions and re­quire specific therapy, such as antiplatelet agents for emboli from large artery atherosclerotic plaque and anticoagulants for cardiac emboli.

Future advances in TCD technology will permit full automa­tion and better identification of the composition and size of circu­lating embolic materials, thus improving its value for patients with cerebrovascular disease.

Contact Colleen Douville, RVT, at colleen.douville@swedish.org or 206-320-4080, for more information about TCD for detec­tion of cerebral microemboli.

 

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