Intermittent dizziness due to a diaphragm of the common carotid artery successfully treated by stenting

Abstract

Carotid diaphragm is considered a form of fibromuscular dysplasia (FMD) that may result in the narrowing of blood vessels, potentially increasing the risk of stroke. More than 50 cases of carotid diaphragm have been reported, most cases of which are located in the internal carotid artery. Patients are usually middle-aged and initially manifest as syncope, tinnitus, and ischemic stroke. In this paper, we report a rare case of septal aneurysm in the common carotid artery (CCA). This is the fourth case reported in the literature.

Introduction

Fibromuscular dysplasia (FMD) is a noninflammatory disease of medium and large arteries, characterized by abnormal development of the arterial wall. It mainly affects the carotid artery, renal artery, and mesenteric artery [1]. Although many ultrasound studios may misdiagnose carotid artery FMD as carotid artery plaques, with the advancement of ultrasound examination technology and the widespread application of triplex ultrasound (US), carotid artery ultrasound remains the most common screening tool for carotid artery FMD [2].

Case report

The patient, a 62-year-old Han Chinese man, came to the hospital due to intermittent dizziness and his symptoms improved after resting. The patient denied any history of smoking, alcohol abuse, diabetes, or hyperlipidemia, and had hypertension for 2 years (the highest blood pressure was 150/90 mmHg). Carotid US was performed and showed 2 diaphragm-like echoes in the distal and middle segments of the right CCA in B-mode. The CCA between the 2 diaphragms was locally widened, with an inner diameter of about 10 mm (Fig. 1). The diaphragms did not swing with the blood flow. Flow on color Doppler was seen at the aperture of the 2 diaphragms. Spectral Doppler showed that the blood flow velocity at the distal diaphragm increased significantly, with a peak velocity of 286 cm/second (Fig. 2), while it was within the normal range at the proximal diaphragm. The blood flow spectrum of the ipsilateral internal carotid artery showed low velocity and low resistance (Fig. 3), indicating severe stenosis of the upstream CCA. No obvious abnormality was found in the remaining carotid arteries. To confirm the diagnosis, the patient underwent further examination. CT-angiography (CTA) showed local aneurysm in the right CCA (Fig. 4), magnetic resonance angiography (MRA) showed local diaphragm-like abnormal signals in the right CCA (Fig. 5), and digital subtraction angiography (DSA) confirmed severe stenosis of the right CCA (Fig. 6). None of the above imaging examinations revealed the presence of ischemic brain lesions in the patient. To relieve the symptoms, carotid artery stenting was performed. An ev3ProtegeRX40 mm × 9 mm self-expanding stent was placed in the right CCA. The contrast agent passed smoothly, and the cerebral vessels were well visualized (Fig. 7). At a follow-up of 6 months postoperatively, the patient did not experience any further neurological symptoms. Repeated triplex US showed unobstructed blood flow in the stent and normal spectrum of the ipsilateral internal carotid artery (Fig. 8, Fig. 9).

Fig. 1.

B-mode US demonstrated 2 diaphragms (arrows) in the right CCA with an accompanying aneurysm in between (lumen between calipers).

Fig. 2.

Triplex US showed severe stenosis at the distal diaphragm. The peak velocity was 286 cm/second, associated with color Doppler aliasing artifacts.

Fig. 3.

Triplex US showed low velocity and resistance of the blood flow spectrum of the downstream ipsilateral internal carotid artery.

Fig. 4.

CTA showed local aneurysm in the right CCA (arrow).

Fig. 5.

MRA showed focal diaphragm-like abnormal signals (arrow) in the right CCA.

Fig. 6.

DSA confirmed local aneurysm of the right CCA (arrow) with focal severe stenosis at its distal tip.

Fig. 7.

Repeated DSA showed that the stent expanded well. The contrast agent passed smoothly, and the cerebral vessels were well visualized.

Fig. 8.

Repeated triplex US at 6-month follow-up showed that the blood flow in the stent was unobstructed.

Fig. 9.

Repeated triplex US at 6-month follow-up showed that the spectrum of the ipsilateral internal carotid artery returned to normal.

Discussion

MEDLINE/PubMed/Embase databases were comprehensively searched for using the keywords “diaphragm,” “septum,” “web,” “common carotid artery,” and “atypical fibromuscular dysplasia,” and only 3 reports of the diaphragm in the CCA were identified [[3], [4], [5]]. The carotid diaphragm represents a nonatherosclerotic cause of ischemic stroke and is considered a subtype of FMD, predominantly affecting the internal carotid and vertebral arteries. The diaphragm is fibrous and presents as a shelf-like intimal flap, which originates from the intima of the common carotid artery [6]. This condition is notably more prevalent among African or African American populations who are under the age of 55 [7]. A recent meta-analysis revealed that the incidence of carotid artery FMD in young patients (under 60 years old) was approximately 13% [8]. FMD is characterized by abnormal muscular development of the arterial wall, potentially leading to aneurysm, dissection, stenosis, or occlusion [9]. All previously reported cases of CCA diaphragms [[3], [4], [5]] were diagnosed by US. In previous studies on the carotid artery diaphragm, US showed lower accuracy than examinations such as CTA [6,10], possibly because most diaphragms are located in the bulb of the internal carotid artery, which is at a relatively high position and is obstructed by the mandible. This case involves a rare diaphragm located in the middle segment of the CCA. Due to the relatively shallow middle segment of the CCA, US can display the 2-dimensional echo of the diaphragm, distinguish arteriosclerotic plaques by observing the morphology of the diaphragm in detail, and distinguish it from carotid artery dissection by observing floating intimal echo. In this case, aneurysmal dilatation can be seen between the 2 diaphragms, extracranial carotid artery aneurysms secondary to the carotid diaphragm are rare [4], potentially attributable to increased intraluminal pressure resulting from severe stenosis of the distal CCA segment caused by the diaphragm. This condition may be misdiagnosed as a dissecting aneurysm of the CCA. Compared with previous studies, this case comprehensively evaluated both intracranial and extracranial vessels through comparative analysis of different imaging modalities, which helped to make a more precise diagnosis and provide a theoretical foundation for future research. Asymptomatic patients are usually treated with antiplatelet therapies (aspirin or clopidogrel bisulfate) [11]. Previous observational data have shown that, despite medical management, symptomatic patients with a diaphragm may have a 20% risk of stroke recurrence in 2 years [12]. Therefore, carotid artery stenting and endarterectomy have become reliable and long-term effective treatment methods [6]. Although there remains a disagreement between carotid artery stenting and endarterectomy to date, carotid artery stenting is regarded as a minimally invasive alternative to revascularization [10]. In this report, the patient presented with dizziness, and US indicated abnormal blood flow distal to the diaphragm. Therefore, less invasive stent implantation was selected. As expected, the stent effectively opened the diaphragm tissue, alleviated carotid stenosis, and no perioperative complications occurred. Follow-up revealed unobstructed blood flow within the stent and no recurrence of neurological symptoms. Our report reaffirms the feasibility of stenting and provides insights into the management of this condition.

Conclusions

This is a case of carotid artery diaphragm with a rare localization in the right CCA. To our knowledge, this is the fourth reported case in this location. This case highlights the multimodal imaging manifestations of this condition and the successful treatment of intermittent symptoms related to significant flow decrease by stenting. Radiologists should be aware of such a rare carotid condition and the role of triplex US in depicting its hemodynamic repercussions.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Patient consent

Written informed consent for the publication of this case report was obtained from the patient.

CRediT authorship contribution statement

All authors contributed to the study conception and design. Writing - original draft preparation: Jingchao Wang; Writing - review and editing: Heping Deng, Jinglin Cao; Conceptualization: Jingchao Wang; Methodology: Jingjie Bai; Formal analysis and investigation: Cong Wang, Yanyang Wang; Funding acquisition: Jingchao Wang; Resources: Jinglin Cao; Supervision: Heping Deng, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.