Elsevier

World Neurosurgery

Volume 83, Issue 2, February 2015, Pages 188-196
World Neurosurgery

Peer-Review Report
Arterial and Venous Aneurysms Associated with Arteriovenous Malformations

https://doi.org/10.1016/j.wneu.2014.05.037Get rights and content

Objective

To identify prioritization based on hemorrhagic risk and indications for treatment of arterial and venous aneurysms associated with arteriovenous malformation (AVM).

Methods

From a global series of 400 consecutively treated AVMs, 34 patients (8.5%) with 45 arterial or venous aneurysms were extrapolated. These 45 lesions were classified as unrelated aneurysms (n = 5 cases; 11.%), flow-related aneurysms (n = 18 cases; 40%), and intranidal and postnidal venous aneurysms (n = 22; 49.%). The 18 flow-related aneurysms were further divided into remote (n = 6 cases) and adjacent (n = 12 cases) types. Of 45 aneurysms associated with AVMs, 15 were unruptured with a 5-year mean follow-up. Various possible risk indicators were considered and measured by univariate and multivariate analyses.

Results

During the follow-up period, 1 of 15 unruptured aneurysms bled, and the patient died. A significantly different bleeding incidence was found between unrelated aneurysm and flow-related aneurysm types (P = 0.002). Bleeding was significantly less probable in flow-related remote aneurysm type than in venous and flow-related adjacent aneurysm types (P = 0.007). The location of the aneurysm was the only true risk factor for bleeding; the other parameters had no influence on bleeding.

Conclusions

In this series, different subtypes of aneurysms associated with AVMs had different clinical behaviors. The bleeding risk of the unrelated aneurysm and the flow-related remote aneurysm types should be considered almost the same as any other unruptured aneurysm. In other words, bleeding risk should be considered taking into account the parameters established by the International Study of Unruptured Intracranial Aneurysms (location, size, and morphology). Conversely, flow-related adjacent aneurysm and venous aneurysm types have significantly higher bleeding potentials.

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.

Section snippets

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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    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.

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