Histopathological Examination of a Symptomatic Carotid Web: A Case Report

Abstract

Carotid webs cause ischemic stroke in young people and are associated with a high rate of stroke recurrence. Histopathological examination is crucial for clarifying the pathogenesis and mechanisms underlying the occurrence of carotid webs, although the mechanisms generally remain unclear. Here, we report a case of a symptomatic carotid web in a woman in her 50s who had a medical history of two ischemic strokes. She was diagnosed with a right carotid web and underwent carotid endarterectomy 18 days after the second stroke. Histopathological examination clearly revealed several phases of intimal hyperplasia. Furthermore, a thrombus attached to the carotid web showed invasion by fibroblasts and capillaries, and organization had begun. We presume that after the appearance of the carotid web, the thrombus formed by stagnant flow and became organized, causing the carotid web to grow and change in shape.

Keywords: carotid endarterectomy; carotid web; cerebral ischemia; stroke; stroke in young adults.

Fig. 1

(A) Diffusion-weighted magnetic resonance imaging demonstrated a high-intensity signal at the right caudate and putamen. (B) Magnetic resonance angiography showed right internal carotid artery occlusion. Digital subtraction angiography at presentation showed that the right internal carotid artery was (C) occluded and then (D) recanalized after mechanical thrombectomy. (E) A small protruding lesion (black arrow) was observed along the posterior wall of the right carotid bulb. (F) The contrast injection cleared the right internal carotid artery, whereas marked contrast stagnation (black arrowhead) was observed distal to the carotid web. (G) A tiny triangular filling defect was present along the posterior wall of the left carotid bulb (black arrow). (H) Diffusion-weighted imaging demonstrated an infarction in the right caudate and putamen after mechanical thrombectomy.

Fig. 2

(A, B) Computed tomography angiography demonstrated a carotid web (white arrowheads) in the right internal carotid artery visible as a septum on axial imaging and a defect of contrast material emerging from the posterior wall. (C, D) A protruding shelf-like lesion (white arrowheads) was observed on sagittal imaging in the left internal carotid artery. (E, F) Magnetic resonance imaging of the vessel wall revealed a curvilinear, intraluminal filling, isointense object along the posterior wall of the right internal carotid artery at its origin (white arrows).

Fig. 3

(A, B) The carotid web had a smooth contour, was in the posterior wall of the ICA, and had a superimposed thrombus (white arrow) over the web pocket. (C) The carotid web was dissected from the intima of the proximal ICA. After removal, the luminal contour became normal. ECA, external carotid artery; ICA, internal carotid artery; CCA, common carotid artery

Fig. 4

(A) Histopathological examination revealed that the carotid web consisted of intimal thickening composed of elastofibrotic tissue of various stages. ①The most proximal portion was composed of dense elastic fibers that were mainly arranged vertically. ②The middle of the web was mainly composed of brown collagen fibers, different from those in the proximal portion. ③The most distal portion of the web appeared to override the two aforementioned portions, where the elastic fibers were arranged horizontally. Localized loss of smooth muscle cells and irregularity in the elastic laminae of the media were observed (white arrow). A fresh thrombus was attached to the end of the web (black arrowhead) (Elastica van Gieson stain, original magnification ×1). (B) Magnification of the black framed area in (A). (C) The most proximal portion of the carotid web was composed of dense elastic fiber proliferation admixed with collagen fibers, and the distal portion had a similar tissue component but more prominent collagen fibers (periodic acid–Schiff–Alcian blue stain, original magnification ×400). (D) Alpha-smooth muscle actin-positive myofibroblasts were observed (original magnification ×400). (E) The thrombus had begun to organize (hematoxylin and eosin stain, original magnification ×400). (F) The thrombus obtained during mechanical thrombectomy revealed signs of organic consolidation mixed with red blood cells and fibrin (hematoxylin and eosin stain, original magnification ×400).