The Train-Line Pattern on Duplex Ultrasound Helps Differentiate Intramural Thrombus from Atheromatous Plaque in Common Carotid Artery Dissection

Abstract

Background/Objectives: Common carotid artery dissection (CCAD) can result in severe neurological sequelae; however, its diagnosis may be challenging due to consciousness disturbance and aphasia. The objective of this article is to propose a new imaging feature to assist in the identification of CCAD. Methods: This retrospective case series enrolled 139 patients with discharge diagnoses of aortic dissection who underwent carotid ultrasound during admission over a period of three years. Results: Among these patients, 23 had type A aortic dissection, and 113 had type B aortic dissection or related conditions. Notably, among the 23 patients with type A aortic dissection, eight had associated common carotid artery dissection (CCAD), and a total of nine CCAD events were identified. Meanwhile, a B-mode ultrasound revealed six double lumens with intimal flaps and three intramural thrombi. The 'train-line' pattern in ultrasonography was discerned by detecting a hypoechoic thickened wall, which was characterized by a margin formed by two parallel linear reflections in close proximity. This distinctive "train-line" pattern was identified in three intimal flaps and two intramural thrombi. Conclusions: While double lumens and intramural thrombus are prevalent findings, the latter may be misinterpreted as atherosclerotic plaque. The "train-line" pattern may aid in distinguishing intramural thrombus from atheromatous plaque, offering an additional diagnostic tool alongside the identification of double lumens with intimal flaps.

Keywords: aortic dissection; carotid duplex sonography; common carotid artery dissection; neuroimaging; stroke diagnosis; train-line pattern.

Figure 1

Study design flow chart of patients enrolled and reasons for exclusion. Abbreviation: CCAD, common carotid artery dissection.

Figure 2

Double lumen with intimal flap with train-line pattern (A–C) and without train-line pattern (D–F). The ultrasound image was obtained using a 4× magnification setting. Yellow arrows indicate the “train line”. The train-line pattern is characterized by two closely positioned, hyperechoic parallel linear reflections overlying a thickened vessel wall. Symbols such as “×”, “+”, arrows, and arrowheads were generated by the ultrasound machine and used by sonographers to mark regions of interest (ROIs) where the intimal flap was located.

Figure 3

Intramural thrombus with train-line pattern (A,B) and without train-line pattern (C). The ultrasound image was obtained using a 4× magnification setting. Yellow arrows indicate the train line. White arrows indicate intramural thrombus. Symbols such as “×” and “+” were generated by the ultrasound machine and used by sonographers to mark ROIs.