From aneurysm to aneurysmal vasculopathies

Intracranial pediatric aneurysms: endovascular treatment and its outcome

OBJECT

The aim of this study was to analyze the location, clinical presentation, and morphological characteristics of pediatric aneurysms and the safety, feasibility, and durability of endovascular treatment.

METHODS

The authors conducted a retrospective study of all cases involving patients 18 years old or younger who underwent endovascular treatment for pediatric aneurysms at their institution between July 1998 and July 2010. The clinical presentation, aneurysm location, endovascular management, and treatment outcome were studied.

RESULTS

During the study period, 23 pediatric patients (mean age 13 years, range 2 months-18 years) were referred to the authors' department and underwent endovascular treatment for aneurysms. The aneurysms were saccular in 6 cases, dissecting in 4, infectious in 5, and giant partially thrombosed lesions in 8. Fourteen of the aneurysms were ruptured, and 9 were unruptured. Thirteen were in the anterior circulation and 10 in the posterior circulation. The most common location in the anterior circulation was the anterior communicating artery; in the posterior circulation, the most common location was the basilar artery. Saccular aneurysms were the most common type in the anterior circulation; and giant partially thrombosed and dissecting aneurysms were the most common types in the posterior circulation. Coil embolization was performed in 7 cases, parent vessel sacrifice in 10, flow reversal in 3, glue embolization in 2, and stent placement in 1. Immediate angiographic cure was seen in 21 (91%) of 23 patients. Complications occurred in 4 patients, 3 of whom eventually had a good outcome. No patient died. Overall, a favorable outcome was seen in 22 (96%) of 23 patients. Follow-up showed stable occlusion of aneurysms in 96% of the patients.

CONCLUSIONS

Pediatric aneurysms are rare. Their clinical presentation varies from intracranial hemorrhage to mass effect. They may also be found incidentally. Among pediatric patients with aneurysms, giant aneurysms are relatively common. Endovascular management is associated with low rates of complications and is a safe, durable, and effective treatment for pediatric aneurysms.

Pathomechanisms and treatment of pediatric aneurysms

Pediatric aneurysms are rare diseases distinct from classical adult aneurysms and therefore require different treatment strategies. Apart from saccular aneurysms that are more commonly found in older children, three major pathomechanisms may be encountered: trauma, infection, and dissection. The posterior circulation and more distal locations are more commonly encountered in children compared to adults, and there is an overall male predominance. Clinical findings are not only confined to subarachnoid hemorrhage but may also comprise mass effects, headaches or neurological deficits. In traumatic aneurysms, the skull base and distal anterior communicating artery are commonly affected, and the hemorrhage occurs often delayed (2-4 weeks following the initial trauma). Infectious aneurysms are mostly bacterial in origin, and hemorrhage occurs early after a septic embolic shower. Dissecting aneurysms are the most often encountered aneurysm type in children and can lead to mass effect, hemorrhage, or ischemia depending on the fate of the intramural hematoma. Treatment strategies in pediatric aneurysms include endosaccular coil treatment only for the "classical berry-type" aneurysms; in the other instances, parent vessel occlusion, flow reversal, surgical options, or a combined treatment with bypass and parent vessel occlusion have to be contemplated.

The aneurysmal wall. The key to a subclassification of intracranial arterial aneurysm vasculopathies?

SUMMARY

The pathogenesis of intracranial arterial aneurysms (AA) has been debated for many years and still remains unclear, although these entities might pose life-threatening risks to the patient and understanding the disease is of utmost importance for choosing treatment concepts. Apart from the "classical" berry-type aneurysm, there are different other types of intracranial AA such as infectious, dissecting or giant, partially thrombosed aneurysms. From the clinician's perspective, the hypothesis that some of these intracranial aneurysms might be due to abluminal factors has been put forward for many years. Alterations of the vessel wall, either due to luminal or abluminal factors may be employed for an etiological classification of aneurysmal vasculopathies as will be discussed in this article. Moreover, regarding certain aneurysmal vasculopathies as an abluminal disease might alter current therapeutic strategies since therapy should not only aim at the intraluminal repair of the artery but may also target the vessel wall.

Intracranial arterial aneurysm vasculopathies: targeting the outer vessel wall

The pathogenesis of intracranial arterial aneurysms (AA) remains unclear, despite their clinical importance. An improved understanding of this disease is important in choosing therapeutic options. In addition to the "classical" berry-type aneurysm, there are various other types of intracranial AA such as infectious, dissecting or giant, partially-thrombosed aneurysms. From the clinician's perspective, the hypothesis that some of these intracranial AA might be due to abluminal factors has been proposed for several years. Indeed, this hypothesis and the empirical use of anti-inflammatory drugs in giant intracranial aneurysms have been confirmed by recent studies reporting that an enzyme involved in the inflammatory cascade (5-lipoxygenase or 5-LO) promotes the pathogenesis of specific aneurysms in humans. 5-LO generates different forms of leukotrienes which are potent mediators of inflammation. Adventitial inflammation leads to a weakening of the media from the abluminal part of the vessel wall due to the release of proinflammatory factors that invade the media, thereby degrading the extracellular matrix, the elastic lamina of the vascular wall, and, finally, the integrity of the vessel lumen. This in turn results in a dilation of the vessel and aneurysm formation. Moreover, neoangiogenesis of vasa vasorum is found in close proximity to 5-LO activated macrophages. In addition to this biological cascade, we argue that repeated subadventitial haemorrhages from the new vasa vasorum play an important role in aneurysm pathogenesis, due to a progressive increase in size mediated by the apposition of new layers of intramural haematoma within the vessel wall. Intracranial giant AA can therefore be regarded as a proliferative disease of the vessel wall induced by extravascular activity. Considering certain aneurysmal vasculopathies as an abluminal disease might alter current therapeutic strategies. Therapy should not only be aimed at the intraluminal repair of the artery, but also cross the vessel wall to reach the vasa vasorum. Drug-eluting stents placed proximal to the lesion and targeted to the origin of the vasa vasorum could be considered as a potential future option. "Intelligent" MRI contrast agents (i.e., macrophage marking) could be used to detect vasa vasorum proliferation and weakening of the vessel wall in vivo.

Complete thrombosis of a giant distal middle cerebral artery aneurysm

SUMMARY

Complete thrombosis of a giant cerebral aneurysm is rarely reported and peripheral giant middle cerebral artery (MCA) aneurysms are similarly rare. We present a case of complete spontaneous thrombosis of a giant sylvian artery aneurysm that had previously been wrapped at surgery.