Extracranial carotid artery aneurysm (thereafter – ECAA) is a rare vascular disease that constitutes 1.5–4% of all cerebral aneurysms (1, 2). Early diagnosis and treatment of ECAA are important as many cases remain asymptomatic until thromboembolic events, cranial nerve compression, or a rupture of an aneurysm. Treatments for this condition represent 0.2–5% of carotid procedures according to the institutional reports (3). Carotid cavernous fistulas (thereafter – CCF) are abnormal communication of the cavernous sinus and the previously normal carotid arterial system (4). The combination of CCF and ECAA is an extremely rare condition that often requires neurosurgical intervention. In this report, we present two clinical cases of this rare combination of pathologies in patients, highlighting the challenges involved in diagnosing and treating this complex condition.

Although some reports about ICA aneurysms with CCF exist (5), and literature on CCF and ECAA separately (6, 7), to our knowledge, this is the first study to present cases of CCF and ECAA combination occurring in a patient. Trauma is the most common cause of direct CCF and dissecting aneurysm. In two cases presented here, patients reported a history of trauma, confirming the recommendation to ask cases of single-hole dural fistula about trauma in case of suspicion of direct CCF (8). A treatment protocol for the two pathologies combination is not established.

In the presented cases, CCF was treated first. It reduced the risk of CCF resulting in hemorrhage from dual antiplatelet therapy. The resulting blood thinning could make the occlusion of CCF slower and more difficult with more materials used due to slow thrombosis. CCF treatment would relieve patients’ acute symptoms.

Different options for CCFs treatment are available, such as conservative management and embolization. Conservative management can be effective in approximately 30% of indirect CCF and 17% of direct CCF cases, but most of these cases had mild clinical presentations (9).

Detachable balloon occlusion is a cost-effective and straightforward option for treating CCFs, but it can lead to complications such as cerebral infarction or CCF recurrence (10). Embolization with the ethylene-vinyl alcohol copolymer Onyx is another treatment option for CCFs. However, using a combination of dimethyl sulfoxide and Onyx can be toxic and pose a potential risk for trigeminocardiac reflex-induced bradycardia (11).

Placement-covered or flow-diverting stents are also used as an alternative method for the treatment of CCFs. Despite dramatic initial improvement, delayed thrombosis remains a problem with the use of currently available covered stents in the cerebral circulation. In the cases presented, balloon-assisted embolization was chosen as the treatment method due to its advantages, such as the lack of complications, practicality, and ability to keep the ICA unobstructed.

The second surgical intervention was ECAA treatment. Surgical approaches include microsurgical resection of the aneurysm, with arterial reconstruction, and endovascular stenting (12, 13). In presented cases, the basis for choosing the latter was the prevention of cranial nerve injuries, which can occur during open surgical repair. Aneurysms near the neck often form from dissection, therefore; stent placement is optimal for the increase of vessel endothelialization. From the self-expandable carotid stent and flow diverter, the former was chosen due to its higher stent cell density, and cost-effectiveness, and demonstrated equal outcomes to the flow diverter (14).

The main limitation of this study is the lack of enough cases. We cannot provide controlled clinical research to demonstrate the availability and efficacy of our strategy. However, follow-up results show a good outcome after 6 months.

The presented cases showed that aneurysm-associated CCF is a complex and risky pathology. Evaluation of the fistula and aneurysm angioarchitecture and digital subtraction angiography is essential. This case report suggests a treatment plan, and multi-step endovascular surgery when encountering CCF and ECAA combination in a patient.

The original contributions presented in the study are included in the article/Supplementary material, further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by The Institutional Review Board of the National Centre for Neurosurgery. The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

All authors contributed to the study’s conception and design. Material preparation and data collection were performed by CN and YM. CN and AK wrote the first draft of the manuscript. SA wrote the final version of the manuscript. All authors commented on previous versions of the manuscript. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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