Ultrasound imaging of carotid web with atherosclerosis plaque: a case report

Carotid webs with atherosclerotic plaques are one cause of stroke; however, misdiagnosis and missed diagnosis of this disease are frequent. Its diagnosis is a challenge for radiologists and sonographers because it is rare and relevant reports are scarce, which in turn affects the treatment and management of the disease. Although previous reports of carotid web exist [1‐18], carotid webs with atherosclerotic plaque formation have not been mentioned in previous studies. Thus, establishing the image characteristics of this disease is vital to improve treatment and outcomes. In this report, we aim to present a case of and provide further information on a carotid web with an atherosclerotic plaque; pathological findings were confirmed after carotid endarterectomy (CEA).

A 61-year-old Han man presented to our hospital with intermittent dizziness and slurred speech for 1.5 years and numbness of both upper limbs for 4 months. After resting, he showed improvement and had intermittent attacks without any treatment. A computed tomography angiography (CTA) examination indicated stenosis at the beginning of the left internal carotid artery. Because of recurrent symptoms, he sought admission to our hospital for further treatment. Moreover, he had diabetes for 17 years and was treated with an orally administered antidiabetic medication. He also had hypertension for 10 months (blood pressure up to 220/120 mmHg) and was treated with an orally administered antihypertensive drug. He had 20-pack years of smoking history.

To understand carotid webs with plaque formation, we should first fully understand a carotid web. The term “web” was first used to describe this disease by Momose and New in 1973 at the Massachusetts General Hospital [7]. They analyzed 7000 carotid angiograms for 8 years and found 4 cases with web-like tissue in the lumen in the cervical portion of the internal carotid artery [7]. Subsequently, relevant studies on carotid webs were reported [1‐5], which suggested that carotid webs are thin membrane structures protruding into the lumen; they are more common in the posterior or lateral posterior wall of the internal carotid bulb, and are approximately eight times more common in patients with stroke than in controls. Moreover, carotid webs are strongly associated with ischemic stroke [3, 8], and they are one of the causes of cryptogenic stroke in young patients [1, 4, 10, 15]. However, they are often missed [11] and could be an underappreciated risk factor for stroke [4, 9]. In addition, carotid webs may contribute to recurrent ischemic stroke [6, 9, 10], despite antithrombotic use and antiplatelet therapy. It is worth emphasizing that the image characteristics of a carotid web with atherosclerotic plaque formation could be easily confused with plaque surface ulceration, especially in geriatric patients. Both radiologists and sonographers may not consider the possibility of this disease and thus make the wrong diagnosis, that is, plaque surface ulcer formation. However, the two diseases are treated differently. Carotid webs with or without atherosclerotic plaques should be treated with antiplatelet therapy, and the most effective and radical treatment is surgical intervention, whereas the treatment of atherosclerosis plaque surface ulceration may include plaque stabilization therapy. Thus, accurate diagnosis is key to preventing strokes and treating the disease. We consider that ultrasound has absolute diagnostic advantages, although reports on the disease diagnosed by ultrasound examination are rare. However, Kliewer and Carroll [13] and Perren F et al. [14] described carotid webs using DUS in 1991 and 2004, respectively, and another case of carotid web by DUS was reported in 2015 [11]. While almost all diagnoses and reports on this disease were based on CTA or digital subtraction angiography, a study in 2017 using DUS reported on a carotid web with a short segment filling defect [15]. Thus, DUS could make an accurate diagnosis and may have the ability to diagnose carotid web. However, an accurate diagnosis depends on the full understanding and careful observation of the image characteristics. In our case, we found that the carotid web with a plaque had similar image characteristics to plaque surface ulcer formation due to the cavity structure; however, substantial differences between the two diseases were noted. The top of ulcer cavities has no membranous structure, while the plaque attached to the base of the carotid web did have a membranous structure on the cavity surface.

Moreover, DUS could show the carotid web and the plaque clearly, that is, the structural and positional relationships between the carotid web and plaque could be clearly displayed on ultrasound. However, slight adjustment of the probe direction is needed to trace the direction and angle change of the membrane structure, and careful observation on multiple angles is necessary. Moreover, high suspicion of the disease may be helpful for the diagnosis. In our case, a minor niche shadow on the lateral wall at the beginning of the internal carotid artery was identified with CTA (Fig. 1) and the carotid web was not found. Therefore, the absence of any suspicion and insufficient recognition of this disease may be the reasons for the misdiagnosis with CTA. After CEA, we observed the fresh tissue and histopathology features of the disease and summarized the image characteristics based on DUS and made a CTA image reconstruction. Interestingly, the manifestations of the carotid web with plaque based on DUS and CTA image reconstruction were similar (Figs. 5, 6, 10, and 11). The filling defect was membrane-like or shelf-like and a cavity was found between the web and the plaque, which could be easily confused with plaque surface ulceration. However, the disease differs from plaque surface ulceration as the surface of the ulcer is eroded and damaged and does not have intact smooth endothelium, whereas the surface of the carotid web with an atherosclerotic plaque is smooth and intact.

Clinicians, including radiologists and sonographers, should be aware that carotid webs with atherosclerotic plaques could occur not only in young patients with stroke but also in elderly patients with stroke. Because the pathogenesis of carotid webs alone versus carotid webs with atherosclerotic plaques are similar, accurately distinguishing the two diseases presents a diagnostic and therapeutic challenge. Thus, careful examination of the diseases is vital to decrease missed diagnosis and misdiagnosis. A previous study reported that early and correct diagnosis of carotid webs is crucial not only to establish the probable cause of stroke but also to prevent the risk of recurrence [2]; thus, adequate understanding of this disease for early diagnosis is critical for the prevention of stroke and recurrence, and for the clinical management of the disease.

However, currently, carotid webs are challenging because of their small and thin characteristics. The low detection rate may be due to a lack of experience, insufficient scanning skills, and limited understanding of the image characteristics. To reduce the rate of missed diagnosis and misdiagnosis, both radiologists and sonographers should increase their familiarization of the image features of the disease. Moreover, acoustic beam direction should be traced along the direction of the carotid web, the whole length evaluated, and the basilar part of the carotid web carefully observed to detect whether the base is attached to the plaque or has thrombus formation. Lastly, high suspicion of the disease could aid in the diagnosis.

In conclusion, DUS could show the morphology of the carotid web with or without plaques; however, improvement in scanning skills is vital. CTA was considered the gold standard for the diagnosis of this disease; however, without adequate knowledge, it could lead to misdiagnosis and missed diagnosis. Early diagnosis of the disease could guide the clinical management of the disease, thereby reducing the incidence and recurrence of stroke.