Peer-Review ReportArterial and Venous Aneurysms Associated with Arteriovenous Malformations
Introduction
Patients with arteriovenous malformations (AVMs) present with a higher incidence of intracranial aneurysms than the general population. Aneurysms associated with AVMs account for 7%–23% in large AVM series 21, 29, 32, 37, but the quoted rates could be even higher using superselective catheterization for digital angiography 11, 25, 29, 38. Several classifications have been proposed for aneurysms associated with AVM 8, 23, 30, 32. They can be grossly divided in prenidal and intranidal and postnidal aneurysms. The former are exclusively arterial lesions and may be subdivided into 1) flow unrelated (UR) type, 2) flow-related remote (FR) type, and 3) flow-related adjacent (FA) type; the latter are exclusively intranidal and postnidal venous lesions (V type) (Figure 1). The natural history of aneurysms associated with AVMs and the proper management strategies are not yet well delineated because the pathophysiology of the different aneurysm types is poorly understood. For instance, data are lacking about the real nature of so-called venous aneurysms and pseudoaneurysms 3, 4, 5, 13, 20, 26, 29, 32. It is now recognized that AVMs usually bleed at the level of the draining veins. These veins frequently have anomalies such as pouches and varices, which may be near or in the nidus of the ruptured AVMs and which are often inappropriately termed “venous aneurysms” 23, 31. These venous dilations are known to carry high potential of rupture. Practically, wrong terminology and misinterpretation of the angiographic findings may lead to the erroneous attribution of elevated bleeding risks to aneurysms associated with AVM rather than to intranidal venous dilations. Such errors can be avoided using superselective angiography, which can provide differentiation between aneurysms adjacent to the AVM nidus (e.g., aneurysms arising on perforators or pseudoaneurysms originating from the rupture of thin-walled vessels) (31) and intranidal venous dilations (Figure 2) (32).
In the present study, from our global series of 400 consecutively treated AVMs, we extrapolated 34 patients harboring 45 aneurysms associated with AVMs. These cases were retrospectively reviewed, and the main features, angiographic patterns, treatment modalities, and outcomes were analyzed and correlated.
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Clinical Data
Over a period of 15 years, 400 consecutive patients underwent treatment for cerebral AVMs at the Department of Neurosurgery of the Niguarda Cà Granda Hospital, Milan, Italy. In this series (9), 199 patients (49.7%) presented with hemorrhage, which was related to aneurysm rupture in 30 cases (15%). The global AVM series also included 4 patients (1%) with associated aneurysm but without any history of cerebral hemorrhage. Accordingly, 34 patients (8.5%) with aneurysms associated with AVMs could
Clinical Outcome and Follow-up
The overall results are summarized in Table 1. Rankin Scale 0–1 was reported in 24 patients (70.6%); 2–3, in 7 patients (20.6%); and 4–5, in 2 patients (5.9%). There was 1 death (2.9%)—the aforementioned patient who died because of the rupture of a residual V type aneurysm while she was waiting for radiosurgery. Severe morbidity was reported in 2 patients (5.9%) and consisted of treatment-related hemorrhages in both cases: 1 case of postoperative hemorrhage requiring reoperation but not
Pathophysiology of Aneurysms Associated with AVM
The term “aneurysm” correctly refers just to a circumscribed dilation of an artery. The term “venous aneurysm” is not nosologically correct and merely refers to a venous varix. However, venous aneurysm entered the common medical jargon and is commonly used in clinical practice 11, 23, 31.
The pathogenesis of AVMs is not completely understood, particularly in regard to associated aneurysms. A role is likely played by the vessel stress owing to overload caused by the arteriovenous shunt. Three
Conclusions
This retrospective analysis of our series showed that the association of aneurysms and AVMs is not exceptional. Most of these aneurysms manifested with hemorrhage, and when hemorrhage occurred, the bleeding lesion was always the aneurysm. Different types of aneurysms associated with AVM carry different hemorrhagic risks. The UR type and the FR type have the same risk as other cerebral aneurysms. In other words, bleeding risk should be considered taking into account their location, size, and
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2019, Journal of Clinical NeuroscienceCitation Excerpt :Cerebral arteriovenous malformations (AVMs) are complicated lesions representing a wide spectrum of pathology. They are frequently associated arterial aneurysms and venous varices, the latter of which carry a particularly high risk of rupture [1]. AVM rupture commonly results in hydrocephalus, but there are a rare number of cases in which hydrocephalus develops as a result of an unruptured AVM [2].
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2018, World NeurosurgeryCitation Excerpt :These “flow-related” aneurysms have been shown to correlate with the presence of hemorrhage, as well as an infratentorial location.3 Flow-related feeding artery aneurysms represent up to 30% of AVM-associated aneurysms and carry a significantly higher risk of bleeding.1,4 Treatment of these aneurysms consists of both microsurgical and endovascular interventions and may be combined with multiple treatment options that address the AVM.5-10
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2018, World NeurosurgeryCitation Excerpt :Hemodynamic aneurysm (HA) associated with arteriovenous malformation (AVM) is generally considered a risk factor for intracranial hemorrhage.1-6
Fistula and Infratentorial Location, Characteristics That Contribute to Cerebral Arteriovenous Malformations, Lead to the Formation of Associated Aneurysms in Patients
2016, World NeurosurgeryCitation Excerpt :cAVMs that are of a high grade or a large size often require multiple procedures before they are obliterated completely, and asymptomatic patients without risk factors for hemorrhage often have been inclined to be treated conservatively. Therefore, a residual or unchanged size of cAVM is observed more frequently, and during the time from diagnosis to the complete obliteration of the cAVM, the residual lesion usually is accompanied by a secondary hemorrhage, which already is a concern for many neurosurgeons.4,10,14-17 This mechanism of hemorrhage in the residual lesion, however, is unclear; it may form a new or recurrent AA, which is deemed a risk factor for hemorrhage.17
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2015, Clinical Neurology and NeurosurgeryCitation Excerpt :The presence of associated aneurysm is noted in 15% of all patients in our series and it causes bleeding in 8% of all patients. These findings support other series in the literature [7,36]. However, incidence of associated aneurysm could be higher than reported in our series, as they are frequently not seen on CTA, particularly intranidal aneurysms.
Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.