Scientific Papers

Carotid free-floating thrombus stemming from carotid web: co-occurrence of two rare causes of ischemic stroke | BMC Neurology

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We report the case of an otherwise healthy young woman who presented with multi-embolic strokes caused by a CFFT stemming from an underlying CaW. The co-occurrence of these two conditions has been reported anecdotally, and the presence of thrombus superimposition on CaW was suggested to be a contributing factor to stroke recurrence [7,8,9,10]. However, there is scarce and heterogenous evidence regarding the effectiveness of antithrombotic and/or interventional treatment as secondary prevention strategies [7,8,9,10]. CaW is a congenital variation in carotid geometry that predisposes to artery-to-artery thromboembolism by disrupting arterial laminar flow and leading to endothelial stress, blood stagnation, and downflow platelet aggregation. This rationale is supported by computational fluid dynamics analysis, which reveals an augmented recirculation zone downstream of the CaW resulting in increased wall shear stress [11]. Additionally, it is corroborated by diagnostic angiography findings, which demonstrate contrast pooling or thrombus detection downstream of the CaW [12]. CFFT, instead, is an acquired condition stemming from either systemic thrombophilia or local vascular wall dysfunction caused by atherosclerosis as well as fibromuscular dysplasia, vasculitis, dissection, and trauma [5, 6]. Hence, chronic endothelial stress withstood by the carotid section distal to the CaW arguably represented a suitable ground for CFFT formation in our patient.

Radiological differentials for CaW encompass atherosclerotic plaque with plaque rupture, carotid artery dissection, and fibromuscular dysplasia (FMD). However, the regular morphology of the filling defect, lack of calcium deposits and signs of intramural hemorrhage make atherosclerotic plaque unlikely in our patient. Furthermore, neither CTA nor DSA revealed the presence of an intimal flap, and no other stenotic segments were identified in our imaging studies, reducing the probability of carotid artery dissection and FMD.

CTA has shown superior diagnostic accuracy compared to carotid US in diagnosing CaW [13]. It is thus expected yet remarkable that the carotid Doppler ultrasound failed to identify the condition in our patient. A plausible explanation could be that the CFFT masked the contiguous congenital anomaly or that lack of knowledge of the possible co-occurrence of the two conditions limited the interpretation of the study. In line with this rationale, we argue that CaW may be a possible undiagnosed cause of CFFT when a complete radiological assessment is not undertaken, especially in young adults without traditional cardiovascular risk factors. Collectively, several radiological CTA and DSA signs helped to discriminate CaW from CFFT in our case. The CaW was located in the posterior part of the internal carotid bulb, below the origin of the CFFT. The linear filling defect was projected perpendicularly to the vessel flow direction in CaW, in contrast with CFFT. The CFFT was partially resolved at DSA, whereas the CaW was still present. Finally, contrast agent stagnation was detected in the carotid web during the DSA venous phase.

As a secondary prevention, our patient was successfully treated with CAS and transitory DAPT. Evidence of the best management is currently lacking in the literature. Indeed, secondary prevention strategies for CaW and CFFT are based on small case series and expert consensus, as no specific guidelines or clinical trials have been designed to date. Concerning CaW prevention, current strategies aim to avoid long-term complications arising from the high stroke recurrence rates. Although chronic pharmacologic management with anti-platelet agents would fall within current guidelines [14] also anticoagulant agents seem an attractive option from the pathophysiological standpoint. Nevertheless, small case series have demonstrated high recurrence rates in patients receiving solely medical treatment [3]. Accordingly, many patients are treated invasively with CAS or endarterectomy (CEA) with satisfactory results [9, 12, 15]. Although CEA was initially the primary proposed invasive treatment option, there is a growing trend towards CAS, particularly in situations involving high surgical risk or anatomical contraindications to CEA [9, 12, 15]. However, it’s worth noting that the relatively young age of many CaW patients introduces challenges, particularly regarding the necessity for long-term antiplatelet therapy [3, 4, 12]. Conversely, CFFT represents a time-sensitive finding with early and urgent management implications where both antithrombotic agents and surgical treatment have been used [5, 6]. Therapeutic implications stemming from the co-occurrence of the two conditions need thus to take into account both the urgent timeframe set by CFFT and the long-term window encompassed by CaW.

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