Internal carotid artery blister aneurysm

An aneurysm arising from the anterior wall of the internal carotid artery (ICA) is a poorly understood entity. A small hemispherical bulge from the anterior wall of the ICA, which is called a “blood blisterlike aneurysm” (BBA), may be confused with a tiny berry aneurysm although the clinical features are distinctly different.

With the improvement in imaging techniques smaller aneurysms are better visualized. This, together with the knowledge that blister type internal carotid artery aneurysms cause subarachnoid haemorrhage and have an appearance that can change over days, should lead to easier diagnosis of this condition. Aneurysms, which are 2 mm or less in diameter and often have a more fusiform than saccular appearance, are referred to as blood blister-like aneurysms (BBA). They occur at non-branching sites of the supraclinoid internal carotid artery (ICA) although they may also be found at the anterior communicating artery ¹⁾.

Blister aneurysms are elusive and technically challenging rare lesions characterized by a hemispherical shape and fragile arterial walls for surgery and endovascular treatment.

The treatment of blister aneurysms of the supraclinoid internal carotid artery (ICA) is challenging and utilizes many therapeutic methods, including direct clipping and suturing, clipping after wrapping, clipping after suturing, coil embolization, stent assisted coil embolization, multiple overlapping stents, flow-diverting stents, covered stents, and trapping with or without bypass. In these therapeutic approaches, the optimal treatment method for BBAs has not yet been defined based on the current understanding of BBAs of the supraclinoid ICA. Therefore, in a study, Ji et al., aimed to review the literature from PubMed to discuss and analyze the pros and cons of the above approaches while adding there own viewpoints to the discussion. Among the surgical methods, direct clipping was the easiest method if the compensation of the collateral circulation of the intracranial distal ICA was sufficient or direct clipping did not induce stenosis in the parent artery. In addition, the clipping after wrapping technique should be chosen as the optimal surgical modality to prevent rebleeding from these lesions. Among the endovascular methods, multiple overlapping stents (≥3) with coils may be a feasible alternative for the treatment of ruptured BBAs. In addition, flow-diverting stents appear to have a higher rate of complete occlusion and a lower rate of retreatment and are a promising treatment method. Finally, when all treatments failed or the compensation of the collateral circulation of the intracranial distal ICA was insufficient, the extracranial-intracranial (EC-IC) arterial bypass associated with surgical or endovascular trapping, a complex and highly dangerous method, was used as the treatment of last resort ²⁾.

In case of ruptured blister aneurysms, Pipeline device has been used with success by administering an abciximab bolus (0.125mcg/kg) IV, approx. 10 minutes prior to device deployment ^{3) 4)}

Treatment of blood blister-like aneurysm (BBA) is a challenge due to its unfavourable morphology, small size and the friable neck of BBA. In the management of ruptured BBA, coil placement can be achieved by stent-assisted coil embolisation. Shinoda et al., propose to incorporate a new technique using a steam-shaped microcatheter to improve safety ⁵⁾.

Preoperative knowledge and careful surgical planning can prevent poor clinical outcomes. Surgical treatment remains an effective and safe option in this context ⁶⁾.

Szumuda et al aimed to define the currently optimal treatment of ruptured BBAs in terms of mortality, outcome, rebleeding, and recurrence.

An in-depth search of electronic databases, gray literature and internet resources for ruptured BBAs was performed and complemented by data retrieval during neurosurgical congresses. Clinical and radiological characteristics, intervention details, outcomes, and the impact factor of the source journal were pooled.

The pooled cohort comprised 311 patients. Neither surgical nor endovascular methods had an impact on clinical outcome, aneurysm regrowth, remote bleeding, or complication rate. By contrast, aneurysm clipping was a predictor of intraoperative bleeding (OR 6.5; 95% CI 1.2 to 34.3), and stent-assisted coiling increased the likelihood of a second treatment (OR 4.1; 95% CI 1.3 to 13.1), its conversion to another modality (OR 4.7; 95% CI 1.4 to 16.0), and incomplete aneurysm obliteration (OR 2.6; 95% CI 1.0 to 6.6). Higher impact journals were more likely to publish papers on endovascular techniques, particularly flow diverter stents.

None of the methods is unequivocally superior. Considering its inefficiency, stent-assisted coiling should be undertaken with caution. A time-delimited systematic review is needed to establish the most accurate treatment for ruptured BBAs ⁷⁾.

These fragile broad-based aneurysms have a propensity to rupture with minimal manipulation during surgical or endovascular explorations because, unlike saccular aneurysms, they lack all layers of the arterial wall. Aneurysm trapping with Extra intracranial bypass surgery is a safe and durable treatment ⁸⁾.

His grim prognosis is based on results that indiscriminately group all blister aneurysms together without taking into account the heterogeneous appearance of these lesions.

Internal carotid artery blister aneurysm case series.

A 59-year-old woman was diagnosed with subarachnoid hemorrhage (SAH) due to a ruptured BBA of the left internal carotid artery (ICA) at the C2 portion. For coil embolisation, Shinoda et al., selected the aneurysm sac using a three-dimensional shaping technique and the jailing method. Post-embolisation angiography revealed complete occlusion of the aneurysmal sac. For safe treatment and stability of BBA, the shape of the catheter tip and the distal portion of the microcatheter are two important factors to consider. The proposed technique could help resolve the problem of catheter shaping in the treatment of BBA ⁹⁾

A 29-year-old man presented with subarachnoid hemorrhage and a ruptured dorsal variant internal carotid artery aneurysm. Despite a technically successful treatment with a single FDS, a second catastrophic hemorrhage occurred during the course of his hospitalization.

This case highlights the risk of hemorrhage during the period after deployment of a single FDS. Ruptured aneurysms, especially of the blister type, are at risk for rehemorrhage while the occlusion remains incomplete after flow diversion ¹⁰⁾.

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Cezar-Junior et al., retrospectively reviewed 15 consecutive cases of patients harboring ruptured BBAs, microsurgically treated at the Department of Neurosurgery, Hospital da Restauração between 2014 and 2018. They performed an analysis of the clinical and surgical aspects, as well as post-operative angiograms and outcomes.

Fifteen patients were identified; 9 (60%) were female. The mean age of presentation was 43,8 years. Most patients presented in good clinical conditions (Hunt and Hess Stroke Scale 1-3 = 86%). The most common Fisher scale at presentation was 3 (60% of cases). All patients underwent digital subtraction angiography (DSA), revealing broad-based aneurysms at non-branching sites on the dorsal wall of the ICA. Intraoperatively, BBAs were confirmed in all cases. The lesions were approached through pterional (11-73%) or lateral supraorbital (4-27%) craniotomy. Direct clipping was performed in all but one lesion, in which case the clip-wrapping technique was used. Final angiographic control revealed complete occlusion in 14 cases. One patient required reoperation due to residual aneurysm filling. At discharge, a good outcome (Glasgow Outcome Scale [GOS] 4 or 5) was observed in 12 (80%) patients. Three patients were discharged with a GOS of 3.

Blood-blister-type aneurysms are rare and challenging lesions. Preoperative knowledge and careful surgical planning can prevent poor clinical outcomes. Surgical treatment remains an effective and safe option in this context ¹¹⁾.