Ultrasound characteristics of carotid web

Abstract

Background and purpose: Carotid web (CaW) is a cause of recurrent ischemic stroke that remains underdiagnosed using Duplex ultrasound (DUS). Improved methods and description of its ultrasound's features could allow better detection of CaW. Ultrasound microflow imaging (MFI) is a blood flow imaging technique sensitive to slow flow that could increase CaW detection. This study aimed to describe ultrasound features of CaW using B-mode imaging and MFI.

Methods: In a retrospective monocentric study, patients with CaW on CT angiography who underwent DUS examination of carotid arteries were included. DUS was performed by two nonblinded experienced neurosonologists. The specificity of CaW ultrasound features was evaluated using a group of patients with carotid atherosclerotic plaque (AP).

Results: Twenty-four patients with CaW were included. Mean age (standard deviation) was 48 years (11). Seventeen (71%) were females. Fifteen (63%) CaWs were symptomatic. MFI was available for 22 patients. B-mode imaging demonstrated the characteristic CaW appearance in 19/24 (79%) patients as a protruding triangular iso-hypoechoic lesion on longitudinal view. CaW were detected on axial view in only 9/24 (38%) patients. MFI displayed slow blood flow above CaW during systole and allowed it delineation, appearing as a thin triangular endoluminal defect in 18/22 (82%) cases. Based on MFI and B-mode, 21/22 (95%) CaWs were visible, including three CaWs only with MFI. These ultrasound features were not found among 24 patients with AP.

Conclusion: We report the ultrasound features from a series of 24 CaW. The use of MFI in addition to B-mode imaging improved the detection rate of CaW.

Keywords: Doppler ultrasound; carotid web; microflow imaging.

FIGURE 1

Typical appearance of carotid web. Longitudinal (A) and axial (B) views of carotid web (CaW) on CT‐angiography. The CaW (arrow) delimits a nest (*). (C) Longitudinal view on B‐mode shows an isoechoic lesion protruding into the arterial lumen (arrow). (D) Corresponding axial view on B‐mode reveals a septum (arrow) delimiting a nidus (*). (E) Microflow imaging delineates the CaW during systole (E) with downstream low flow velocities during diastole (F)

FIGURE 2

Longitudinal view of carotid bifurcation showing carotid web (CaW) in four patients. The CaW appears as an iso‐ or hypoechoic lesion with a thin hyperechoic inferior edge (arrows)

FIGURE 3

Axial view of internal carotid artery showing a carotid web (CaW) in four patients. The CaW appears as a thin transverse septum (arrows) separating the nest (*) from the circulating lumen

FIGURE 4

Anechoic carotid web (CaW) revealed by microflow imaging (MFI) mode. The CaW cannot be demonstrated on B‐mode imaging (A) and is revealed by MFI. Longitudinal and axial view during systole (B and C) and during diastole (D and E). CaW appearance on CT‐angiography in the same patient: longitudinal (F) and axial (G) view. Arrow: carotid web; *: nest

FIGURE 5

Atherosclerotic plaque on microflow imaging (MFI). Atherosclerotic plaque on CTA (A and B) and MFI (C and D). The MFI‐mode during systole delineates a mostly anechoic plaque with a small calcification and without area of low flow on longitudinal view (C). The axial incidence shows a convex anechoic thickening of the artrial wall without nidus (D)