Giant Basilar Artery Aneurysm in the Adolescent Patient: Case Report and Literature Review

Common risk factors for the development and rupture concerning all intracranial aneurysms, counting basilar artery aneurysms,2 include female sex, family history, connective tissue disease, past SAH and hypertension. Vertebrobasilar aneurysms account for 10% to 18% of all intracranial aneurysms, and 50% to 65% of these lesions occur in the basilar bifurcation. Although not as common as aneurysms of the anterior circulation, lesions of the posterior circulation seem to be associated with higher risks and worse prognosis. Another large meta-analysis examining both patient and aneurysm characteristics as risks for rupture found an increased relative risk of rupture 2.5 for aneurysm’s in the posterior circulation, one of the valuable predictors for rupture class with increasing size and symptomatic lesions [25, 26].

This has been borne out for both unruptured and ruptured aneurysms in several studies. Regarding the former, the International Study of Unruptured Intracranial Aneurysms (ISUIA) found that posterior circulation aneurysms of all sizes had a higher 5-year rate of rupture compared with similar size of cavernous and anterior circulation aneurysms. A Japanese single institution series also found a hazard ratio of 2.9 for unruptured aneurysms of the posterior circulation, a similar trend demonstrating the increased risk of rupture for this location [27].

The use of flow-diverting stents is likely to further improve the outcome of patients with giant aneurysms, but data on long-term outcomes for these devices are still pending, and their use may not be the optimal treatment modality in all cases. [28, 29] Despite significant advancements in the neurovascular field, the substantial information and reported outcomes for the safe and total obliteration of giant aneurysms remain from surgical cases.

Nevertheless, it has been proposed that the outcomes of cerebral flow diversion may not be applicable to children due to basic differences between intracranial aneurysms in adults and children [30]. Although endovascular treatment with flow diverters has shown good angiographic results, high complete occlusion rates [31, 32] and acceptable overall procedure-related morbidity in adults, there is a higher risk of unfavorable outcomes in posterior circulation aneurysms and giant aneurysms, which are more frequently encountered in the pediatric population [33].

Based on our results, we believe that flow diverters can significantly enhance the endovascular treatment of cerebrovascular disorders. However, in present case, the discrepancy in stent size—since there was no equivalent stent-size available at the time of the operation—caused the proximal part of the stent to migrate into the aneurysm cavity. So, we do not have in order sufficient length of the stent to be hooked into the current vessel.

Therefore, several issues still require further clarification.

The first issue is children’s growth. The ongoing growth of cerebral vessels in children has been identified as a potential pitfall by some authors [34, 35] or even as a contraindication for cerebral stent placement or flow diversion in this age group [36]. According to Waitzman et al, cranial growth is rapid during the first year of life, slows markedly in later years, and is almost complete by age 6 [37]. Arat et al 28 showed that by 48 months of life, 81%–99% of adult diameters were attained in intracranial arteries; however, only 59% of adult diameters were attained for the common iliac artery [38]. Later, similar findings regarding children were also reported by He et al. From a morphometric standpoint, these studies suggest the following: The size range of current intracranial stents or flow diverters is sufficient to cover the pediatric population, and intracranial arterial diameters in children do not undergo striking growth, especially after early childhood. Thus, the implication that stent placement could cause in intracranial stenosis or similar complications later in life is not supported by the current literature [39].

The second issue that concerns us the most is the pre-/post-procedural antiplatelet medication protocols as there is no standard antiplatelet/anticoagulant therapy for children undergoing intracranial placement of vascular scaffolds (ie, stents, stent grafts, or flow diverters). Reviewing 35 case reports on the placement of cerebral vascular scaffolds in children, we discovered that the use of antiplatelet agents for endovascular treatment was extremely variable [35]. There are neither guidelines published on antiplatelet therapy (APT) in children with cerebrovascular diseases 25 nor conclusive trials on pediatric APT regimens [40, 41].

In this case, due to the constitutional characteristics of the patient weighing >60 kg and the child being >14 years of age, we decided to use 180 mg Ticagrelor per day prior to surgery as with the adult dosage.

Endovascular coiling has been deemed the most effective treatment for aneurysms of this location due to its better patient outcomes than surgical treatment as had shown in randomized clinical trials [41]. However, endovascular coiling alone is not always feasible for complex and/or fusiform aneurysms, even if stent-assisted coiling or balloon-assisted coiling is performed [42]. If endovascular coiling fails, surgical treatment with bypass surgery and aneurysm trapping is a possible treatment modality for these complex BA cases, but it requires surgical experience and has a high rate of complications [43].

But in this case, localization in the posterior circulation presented a great difficulty in the form of a high risk of possible complications. Our clinic uses a trapping method for giant aneurysm of ICA’s. [44] Due to the presence of both posterior communicating arteries, we decided to direct trapping of the middle third of the basilar artery.

Drake et all. performed trapping of the involved segment of the basilar artery in two of 13 patients with aneurysms of the giant basilar trunk [46]. 7 cases in his series were treated with Gunther ligation of the basilar artery due to basilar artery aneurysms with or without rupture, and 5 cases experienced 50% success in aneurysm thrombosis without a significant neurological deficit.