Carotid Web as a Cause of Ischemic Stroke in Sub-Saharan Africa: A Preliminary Monocentric Descriptive Study of 6 Cases Collected at the Fann Teaching Hospital (Senegal)

Introduction: Carotid web (CW), a rare and probably unknown arterial cause of ischemic stroke (IS), is commonly reported in young black patients, al-though most of the published cases resided in a non-African country. We describe the features of the first six Senegalese cases diagnosed at the Neurology Department of the Fann Teaching Hospital in Dakar. Patients and Method: It was a preliminary retrospective and prospective study conducted at the Neurology department of Fann teaching hospital (Dakar-Senegal). The symptomatic CW diagnosis was based on angioCT-scan of the neck arteries. The National Institute of Health Stroke Scale (NIHSS) and the modified-Rankin Scale (mRS) were used to assess the severity of the IS and the functional disability after the event, respectively. Results: CW was causing a left sylvian infarction in 4 patients. The mean age of the patients at the IS diagnosis was 41 ± 6 years with a sex ratio of 1. The mean time to diagnosis of CW was 13 months. Smoking (1/6), hypertension (1/6), and obesity (1/6)


Introduction
Stroke, a major public health burden, occurs in 25% of cases in people aged less than 65 years [1] [2]. In our low-income countries, where stroke units and specific revascularization treatments (thrombolysis, mechanical thrombectomy) are not very developed, secondary prevention is a major issue in the management of ischemic stroke (IS), which represents 85% of strokes.
Carotid web (CW), an atypical form of fibromuscular dysplasia (FMD), is a rare and probably unknown arterial cause of IS in young patients [3] [4]. It is frequently observed in black patients, but most of published cases have been reported in a non-African country [3]- [9].
Our study aim was to describe the diagnostic and therapeutic aspects of Senegalese patients living in Senegal, affected by IS secondary to a CW.

Patients and Method
This was a preliminary retrospective and prospective observational study, which was conducted over 12 months (April 2020-March 2021), at the Neurology department of Fann Teaching Hospital (Dakar-Senegal). Patients were recruited through the post-stroke neurovascular registry. Patients with ischemic stroke before the beginning of the study, were called for a re-reading or to perform an angioCT-scan of the cervical arteries in order to identify an unrecognized CW. Prospectively included patients had systematically an angioCT scan to detect a potential WC.
The diagnosis of symptomatic CW was confirmed if it was homolateral to the cerebral ischemic lesion, in the absence of ischemic sequelae in other vascular territories and of any other evident cause after an adapted minimal etiological evaluation including cardiac, vascular and biological examinations ( Table 2). Patients were excluded if their imaging was not of good quality.
Epidemiological, clinical, radiological, therapeutic, and outcome characteristics were collected in Microsoft Office Excel® 2019. The National Institute of Health Stroke Scale (NIHSS) and modified-Rankin Scale (mRS) scores at 3 months were used to assess IS severity and functional disability, respectively. The means, standard deviations, and medians were calculated with Epi Info 3.5.4 software. Medical record confidentiality and patient identity were strictly respected.

Results
Between April 1, 2020, and March 31, 2021, 6 cases of CW were collected, causing left sylvian infarction in 4 patients (67%) and right in 2 others (33%). CW was unilateral in 3 patients and bilateral in 3 others. The clinical and radiological characteristics of the patients are summarized in Table 1, Figure 1 and Figure 2.
The average age of the patients at the ischemic stroke diagnosis was 41 ± 6 years and the median age was 43 years (32 -46) with a sex ratio of 1. The average time to CW diagnosis was 13 months with extremes of 1 day and 33 months. Half of the patients had no known vascular risk factors before the neurovascular event. One patient was a smoker, one had essential hypertension, and one was obese. The mean initial NIHSS was 15 ± 6 (8 -22). Half of the patients had a severe infarction (NIHSS ≥ 15). The etiological workup performed for each patient is listed in Table 2. On admission, the mean LDL cholesterol level was 1.52 g/L ± 0.49.
None of the patients had received intravenous thrombolysis or later radical CW treatment (endarterectomy or carotid stenting). For secondary prevention, half of the patients were treated with aspirin and the other half with acenocoumarol. Two angio CT-scan were performed in four patients (67%). After a mean     follow-up time of 18 ± 17 months (2 -40), the mean mRS score was 2 ± 1 (1 -3).
No clinical ischemic recurrence was observed.

Discussion
The worldwide prevalence of CW is higher in countries with a majority of African descendants [4] [5] [6] [8] [9] [10]. Therefore, this prevalence could be similar or even higher in sub-Saharan Africa where stroke has a significant socioeconomic impact by affecting younger subjects than in developed countries [11].
In the literature, we did not find any clinical cases or series of patients with CW published in sub-Saharan Africa. A case of internal carotid artery dissecting aneurysm secondary to focal dysplasia has been reported in Côte d'Ivoire [12]. Thus, we report the first CW series in sub-Saharan Africa. It concerns 6 cases of ischemic stroke in young subjects for whom no other cause was identified apart from a web-carotid, despite a first-line etiological investigation that was well conducted in our work context. More and more, CW is recognized as a cause of IS, mainly if it occurs in a relatively young person, with few or no vascular risk factors, like in our series [4] [5] [6] [8] [9] [10] [13] [14] [15]. However, we did not find a female predominance, in contrast to what is commonly described in the literature [16].
The relative rarity of CW is due to the fact that it is most likely under diagnosed because of its potentially misleading morphology and the lack of familiarity of clinicians and radiologists with this carotid disease. It is responsible for ipsilateral recurrent IS despite the use of anti-platelet aggregation [5] [17]. Its diagnosis is therefore the key to effective secondary prevention.
The angio CT-scan of cervical arteries has the advantage of allowing a fine analysis of the lesion on the three views (sagittal, coronal and axial). It is on the axial views that the web appears as a complete cleavage of the lumen, thus separated into 2 parts on either side of the membrane. This is a specific sign of CW, named "hamburger sign" by some authors [15]. Therapeutically, only radical treatment by endarterectomy or stenting would be definitively efficient without ischemic recurrence or postoperative complications [4] [9] [18]. In Senegal, only endarterectomy is performed, so far only for symptomatic atheromatous carotid stenosis. For secondary prevention, all 3 patients prospectively included were on acenocoumarol. Our therapeutic attitude could be justified by the lack of radical treatment and by the pathophysiological mechanisms underlying arterio-arterial embolization during CW [13] [16] [19] [20].
Our study has several limitations including the very small population size and the lack of histological evidence of CW. In additional, the mean follow-up over 18 months is relatively short to detect all possible IS recurrences, particularly as 3 patients were diagnosed prospectively, with a maximum 2 months follow-up.
Thus, further studies with more patients and longer follow-up are ongoing.

Conclusion
At the end of this preliminary study, which is ongoing, we confirm that CW is an unrecognized cause of IS in young black patients. It is crucial to make the diagnosis early and to propose an adequate multidisciplinary management in or-