Vein of Galen Aneurysmal Malformation

23 Vein of Galen Aneurysmal Malformation

Lee-Anne Slater, Brian Drake, Peter Dirks, and Timo Krings

Abstract

Vein of Galen aneurysmal malformations (VGAM) are a challenging pediatric neurovascular shunting disease that require a multidisciplinary treatment approach in a specialized center accustomed to treating these rare malformations. Clinical and radiological features of VGAM, their association with outcome, and decision algorithms of when and how to treat are presented based on the pertinent literature and the authors’ experience. In our experience, treatment is offered based on clinical presentation of the child and is typically done through a transarterial approach employing undiluted glue employing a staged approach to permit normal neurological development and a stepwise reduction of the shunt.

Keywords: pediatric vascular malformations, vein of Galen aneurysmal malformations, embolization, interventional neuroradiology, endovascular treatment

Key Points

Vein of Galen aneurysmal malformations (VGAM) are arteriovenous fistulas involving the median vein of the prosencephalon.
In our practice, children who are not presenting with heart failure or hydrocephalus are medically managed in the first weeks of life and endovascular treatment is performed when the child is around 3 months of age.
Pretherapeutic clinical and imaging evaluation of the child is critical to determine both the appropriateness and timing of endovascular treatment.
Melting brain and multi-organ failure are contraindications to treatment.

23.1 Introduction

Vein of Galen aneurysmal malformations (VGAM) are high-flow intracranial arteriovenous shunts that develop early in the embryonic period involving the choroidal circulation and the median prosencephalic vein (MPV), the embryonic precursor to the vein of Galen. They account for up to 37% of all pediatric vascular malformations. The use of routine antenatal ultrasound (US) for screening has resulted in an increase in the number of these cases being diagnosed in utero and as a result, physicians are now required to counsel parents regarding the condition and potential management strategies. Although overall VGAM are believed to be associated with poor outcomes, a better understanding of this disease, centralization of cases in high-volume centers, and better material have led to a significant number of patients with good clinical outcome. An understanding of the clinical, imaging, and angiographic features of this condition may assist in prediction of outcome and thus permit the physician to appropriately select patients that may benefit from treatment. Scoring systems have been proposed to try and assist in predicting outcome and the appropriateness and best time for treatment if indicated.

This chapter aims to present the clinical and radiological features of VGAM and demonstrates how they can be used to predict outcome. In addition, the rationale for deciding if and when treatment is indicated will be presented along with an introduction to the management and endovascular treatment of this condition.

23.2 Materials and Methods

This chapter presents a combination of previously published articles, information obtained from institutional experience, and the personal experience of the authors. Clinical cases are used to illustrate the principles of treatment decision making as well as the endovascular management of VGAM.

23.3 Results

The analysis of previously published articles, institutional and personal experience, and clinical cases demonstrates the importance of recognizing VGAM and the clinical features and using them to help guide management decisions as well as the timing of treatment. In our practice, endovascular treatment of VGAM is performed, where possible, when the child is 3 months old with medical management and strict clinical follow-up of the child maintained in the interim. Failure of medical management, failure to thrive, a deviation in head circumference, or cognitive development should prompt earlier treatment. Conversely, if a child has a poor clinical score, or melting brain syndrome on magnetic resonance imaging (MRI), treatment should not be offered because in these patients intervention is likely futile.

23.4 Discussion

23.4.1 Introduction

VGAM account for up to 37% of all pediatric vascular malformations.¹ They occur early in the embryonic period and involve multiple shunts between the choroidal circulation and the MPV, the precursor to the vein of Galen. There are two types: the choroidal and mural types. The mural type is characterized by a few high-flow shunts into the anterior wall of the MPV. The choroidal type is characterized by multiple, often smaller, shunts through an arterial network prior to entering the MPV. Combinations of choroidal and mural types are possible.²

23.4.2 Presentation

With the widespread use of antenatal screening US, the prenatal diagnosis of VGAM is increasing. The diagnosis is made by identifying the dilated MPV; however, despite VGAM developing early in the embryonic stage at around 7 to 8 weeks of gestational age, there is usually insufficient dilatation to be detected until the third trimester.³^,⁴^,⁵^,⁶^,⁷^,⁸^,⁹^,¹⁰ There is no evidence that in the absence of multi-organ failure or brain parenchymal changes, an antenatal diagnosis of VGAM is more likely to be associated with a poor outcome and as such does not necessarily constitute an indication for therapeutic abortion. However, a prenatal diagnosis does permit preparation for appropriate neonatal postdelivery care. The most common presentation in the neonatal group is high-output cardiac failure.⁸ Hydrodynamic disorders such as hydrocephalus and increasing head circumference are typically seen as the presenting feature in infancy.²

23.4.3 Natural History

VGAM, if left untreated, are associated with a poor outcome, and only a minority of untreated children with VGAM will do well.³^,¹¹^,¹² Lasjaunias et al proposed a clinical scoring system to assist in determining the timing of treatment called the Bicêtre Neonatal Evaluation Score (► Table 23.1).³^,¹¹^,¹³ This scoring system assesses cardiac, cerebral, respiratory, hepatic, and renal systems with points lost for decreasing function in any of these categories. The maximum score is 21 and it is suggested that in neonates with scores less than 8, treatment should be withheld given they are unlikely to do well despite aggressive intervention. Subsequent to the development of this score, radiological and angiographic features suggested to be associated with poor outcome have included encephalomalacia, intraparenchymal calcifications, and angioarchitecture consisting of choroidal type nidus or jugular stenosis without cavernous drainage. Geibprasert et al evaluated clinical, imaging, and angiographic features that may predict outcome in VGAM patients and found that neurological symptoms at presentation, a medium to low overall neonatal score (< 12/21), a very poor score (< 2/5) in one or more categories of the Bicêtre neonatal evaluation score, focal parenchymal changes, calcifications, tonsillar herniation, arterial steal, or more than two groups of multiple arterial feeders were significantly associated with a poor outcome.²