Other Applications of Extracranial Duplex Screening

Duplex technology can determine if stroke patients have carotid lesions other than atherosclerosis. Examples include carotid thromboembolism, dissection, fibromuscular dysplasia, and radiation injury. These lesions have distinctively different appearances on B-mode ultrasound,

Figure 1 High-risk plaque types and artery-to-artery embolization. (Upper left and middle panels) Hypoechoic plaque on B-mode is marked by arrows; 1, shadows produced by calcified aspects of the predominantly echolu-cent plaque; 2, hypoechoic area with a thin cap near the vessel lumen indicates possible intraplaque hemorrhage or soft and vulnerable part; 3, hypoechoic area on the near wall. Source: Courtesy of Dr. Eva Bartles-University of Gottingten, Germany. (Upper right panel) Ulcerated plaque in a young woman with recurrent episodes of left-sided weakness. Insert shows color flow image that demonstrates slow reversed flow in the crater of an ulcer. Source: Courtesy of Drs. Disya Ratanakorn and Charles Tegeler-Wake Forest University, Winston Salem, NC. (Lower panel) PMD-TCD demonstration of real-time, artery-to-artery embolization in the MCA distal to a severe carotid stenosis. Velocity increase indicates improvement in the residual lumen with thrombus departure and propagation. Diffusion-weighted image demonstrates ischemic foci due to embolic shower. Abbreviations: ACC, common carotid; ACI, internal carotid arteries; MCA, middle cerebral artery; PMD-TCD, power-M-mode-transcranial Doppler.

Figure 1 High-risk plaque types and artery-to-artery embolization. (Upper left and middle panels) Hypoechoic plaque on B-mode is marked by arrows; 1, shadows produced by calcified aspects of the predominantly echolu-cent plaque; 2, hypoechoic area with a thin cap near the vessel lumen indicates possible intraplaque hemorrhage or soft and vulnerable part; 3, hypoechoic area on the near wall. Source: Courtesy of Dr. Eva Bartles-University of Gottingten, Germany. (Upper right panel) Ulcerated plaque in a young woman with recurrent episodes of left-sided weakness. Insert shows color flow image that demonstrates slow reversed flow in the crater of an ulcer. Source: Courtesy of Drs. Disya Ratanakorn and Charles Tegeler-Wake Forest University, Winston Salem, NC. (Lower panel) PMD-TCD demonstration of real-time, artery-to-artery embolization in the MCA distal to a severe carotid stenosis. Velocity increase indicates improvement in the residual lumen with thrombus departure and propagation. Diffusion-weighted image demonstrates ischemic foci due to embolic shower. Abbreviations: ACC, common carotid; ACI, internal carotid arteries; MCA, middle cerebral artery; PMD-TCD, power-M-mode-transcranial Doppler.

and their hemodynamic significance is determined using Doppler spectral data. When found, these lesions point to a specific stroke mechanism other than large-vessel atherosclerosis, and determination of such a mechanism can change treatment options for stroke patients.

Another role of extracranial duplex scanning is to determine the presence of vertebral arterial lesions in patients with neurologic symptoms that refer to the posterior cerebral circulation. Duplex ultrasound allows segmental assessment of the vertebral artery flow between transverse processes and visualization of the vertebral artery origins (24,25). These segments should be thoroughly evaluated in patients with stroke or TIA in the posterior circulation. The spectrum of vertebral pathology detectable by duplex scanning includes vertebral artery stenosis (origin, V2, V3, and V4 segments), vertebral artery occlusion or absence of flow due to congenital aplasia, hypoplastic vertebral artery, and subclavian steal.

On duplex, a finding of significant (greater than 50%) vertebral stenosis or occlusion with evidence of plaque formation indicates that the mechanism of cerebral ischemic symptoms is likely large-vessel atheromatous disease. Infrequently, duplex examination may show vertebral artery dissection (26), and further testing is required to determine if it is an isolated vertebral dissection or an extension of aortic arch dissection. Further consideration should be given as to whether this dissection is spontaneous or trauma related.

Finally, the finding of subclavian steal, most often a harmless hemodynamic phenomenon, indicates the presence of atherosclerotic stenosis or occlusion in the subclavian artery. Occasionally, subclavian steal can produce symptoms related to transient hypoperfusion in the basilar artery (27,28).

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