Balloon-assisted coil embolization of an internal carotid artery pseudoaneurysm in a patient with post-traumatic orbital symptoms

A 37-year old male presented with persistent right-sided vision loss and orbital swelling following a vehicular accident four months prior. On ophthalmologic examination, no light perception was elicited from the right eye. Bruit, proptosis, lower lid retraction, and chemosis were also observed in the right orbit.

Conventional angiography showed a direct type of carotico-cavernous fistula [CCF] arising from the proximal cavernous segment of the right internal carotid artery [ICA] (Figure 1). There was early opacification of the right cavernous sinus. Reflux of contrast material into the dilated posterior segment of the superior ophthalmic vein was observed, but not further distally to its anterior segment. Endovascular treatment of the CCF was offered to the patient.

Two weeks after the initial angiography, the patient was scheduled for embolization. However, repeat angiography showed spontaneous occlusion of the CCF. Instead, a pseudoaneurysm was now visualized in the proximal vertical portion of the cavernous ICA, corresponding to the previous fistula site (Figure 2). Its sac measures 4.6 x 3.8 mm, while its base measures 4.5 mm. The pseudoaneurysm was then embolized with detachable coils, assisted by balloon catheter inflation across the aneurysm base during coil deployment (Figure 3).

Intracranial pseudoaneurysms are rare, accounting for only 1% of all intracranial aneurysms [1]. The most common cause is trauma, while other etiologies include infection, radiation necrosis, malignancy, connective tissue disease, and iatrogenic events. They occur when the vessel wall is disrupted, with subsequent formation of a contained hematoma in communication with the lumen of the ruptured artery. Unlike the more common true aneurysms, they lack true arterial walls and are bound only by fragile connective tissues. As such, they are more prone to rupture, and mortality has been reported to reach as high as 50% in untreated cases [1].

Clinical presentation varies depending on the aetiology, location, and size of the pseudoaneurysm [2]. Its most common presentation is intracranial haemorrhage, either delayed or immediately following the initial injury [1]. Pseudoaneurysms in the cavernous ICA can erode into the sphenoid sinus and present with epistaxis. Due to their proximity to the cavernous sinus and cavernous cranial nerves, they can also present with cranial nerve deficits, unilateral blindness, or CCF [1,3]. Other presentations include headache, seizure, bruit or thrill, acute cerebral ischemia, recurrent cerebral embolism, and other cerebrovascular events [1,2].

Digital subtraction angiography (DSA) is the gold standard for the diagnosis of intracranial pseudoaneurysms, while CT and MR angiographies are alternative, less invasive techniques but less sensitive for small pseudoaneurysms [1,4]. The typical appearance is a globular sac with no discrete neck. On DSA, delayed filling and stagnation of contrast material may be seen. Investigation protocols vary according to institutional practice, although repeat angiography is often warranted in post-traumatic cases when the initial imaging is negative due to the possibility of delayed development of the pseudoaneurysm [1,4].

Early treatment of ICA pseudoaneurysms, whether ruptured or unruptured, is important due to their high morbidity and mortality. In the past, surgery was the treatment of choice; however, with improvement in endovascular techniques, this approach has become increasingly popular and provides a less invasive option [2,5]. Endovascular options include coil embolization with or without balloon or stent assistance, covered stenting, flow diversion stenting, and parent artery occlusion. The choice of treatment depends on several factors, which include the age and clinical status of the patient, aetiology, location and size of the lesion, and presence of collateral circulation [1,2,5].

In the case of our patient, coil embolization was performed to occlude the pseudoaneurysm sac, and balloon assistance was employed due to its wide neck to prevent coil dislodgement. Balloon assistance was preferred over stenting due to the need for long-term antiplatelet therapy in the latter, something we wanted to avoid given our patient’s age and lack of comorbidities. Parent artery occlusion is usually reserved for distal pseudoaneurysms with good arterial collaterals and was not considered in our case due to the possible ischemic complications when performed in the ICA [1]. One disadvantage of coil embolization is the intraprocedural risk of perforation, especially in the acute phase when the pseudoaneurysm wall is still fragile. There is also concern for post-procedural recanalization and rebleeding due to the possibility of coil impaction [1,2].