Benefit of echocontrast-enhanced transcranial color-coded duplex ultrasound in the assessment of intracranial collateral pathways

Background and Purpose-Although clinically important, proper assessment of intracranial arterial collateral pathways by transcranial color-coded duplex sonography (TCCD) in patients with internal carotid artery (ICA) high-grade stenosis or occlusion is occasionally made difficult by an insufficient temporal bone window, an unfavorable insonation angle, or low flow velocity or volume. In these cases, echocontrast could be helpful to increase the diagnostic confidence or to make the diagnosis at all. Methods-We investigated 50 temporal windows of 44 patients with ipsilateral high-grade (greater than or equal to 70%) ICA stenosis or occlusion and insufficient native transtemporal insonation conditions before and after the application of the echo enhancer Levovist with an infusion pump. Results-Compared with the precontrast scans, echocontrast allowed for more segments to be evaluated by pulsed Doppler sonography (P<0.0001) and for longer lumen segments to be displayed on color mode (P<0.0001). Also, collateral flow via the anterior and posterior communicating artery could be demonstrated in 25 and 32 scans, respectively, compared with only 1 demonstration of each collateral pathway before the application of contrast medium (both P<0.0001). Similarly, with the help of contrast medium, now velocity in the middle cerebral artery could be measured in 45 cases compared with only 26 cases before contrast was applied (P<0.0001). Conclusions-In patients with poor precontrast visualization of intracranial arteries, echocontrast-enhanced TCCD is very helpful in the assessment of intracranial collateral pathways recruited downstream to ICA stenoses and occlusions.