Vein of Galen Aneurysmal Malformation and Its Varied Outcomes: An Updated Literature Review

Abstract

Vein of Galen aneurysmal malformation (VGAM) is a rare congenital arteriovenous malformation of cerebral blood vessels with an incidence of approximately 1 in 25,000 live births. This embryonic malformation results from an abnormal arteriovenous connection between the primitive choroidal arteries and the median prosencephalic vein of Markowski. Though it occurs between the 6th and 11th weeks of gestation, prenatal diagnosis is possible only in the second or third trimester due to its slow growth. If left untreated, this significant shunting results in a substantial vascular steal phenomenon and also leads to cardiac failure, hydrops, and perinatal death. Prenatally diagnosed VGAM carries a poor prognosis when associated with cardiac failure or cerebral damage. Prenatal diagnosis is done by ultrasound complemented by magnetic resonance imaging of the fetal brain, while postnatal confirmation is by magnetic resonance angiography. Digital subtraction angiography is considered the gold standard for the evaluation of angioarchitecture. Though spontaneous resolution of VGAM has been rarely reported in the literature, the introduction of endovascular embolization techniques has paved the way to successful treatment of VGAM, with the potential of minimizing mortality and maximizing favorable neurodevelopment outcomes. In this study, we report three cases of prenatally diagnosed VGAM and their varied outcomes, wherein one infant had a spontaneous resolution of VGAM with normal neurodevelopment, another infant had a stormy postnatal course followed by endovascular embolization and normal neurodevelopment, while the third neonate succumbed to the effects of VGAM. We also provide a comprehensive review of literature elaborating the current understanding and management of VGAM, etiopathogenesis, classification, tools of prenatal detection, clinical characteristics, and available prenatal and postnatal treatment options.

Keywords

vein of Galen malformation - arteriovenous malformation - arteriovenous fistula - postnatal outcome - endovascular treatment

Introduction

The first case report of vein of Galen aneurysmal malformation (VGAM) was published in 1946 by Jaeger and Forbes, where the diagnosis was made by necropsy of a four and a half years old boy who had a history of a large head at birth, recurrent nose bleeds, dilated neck and forehead veins, and an enlarged heart.[1] VGAM is a rare congenital malformation of the cerebral blood vessels with a male predominance and accounts for less than 1% of fetal cerebral vascular malformations. However, they represent 30% of intracranial vascular malformations among the pediatric age group.[2] [3] Though ultrasound (US) imaging is crucial in the diagnosis of VGAM, prenatal diagnosis is possible only in less than 30%, especially before the third trimester.[4] [5] Development of cerebral vasculature occurs between 6 and 11 weeks of embryonic life through prechoroidal and choroidal phases. In the choroidal phase, the arterial supply to the developing brain is through choroidal arteries (CAs), and venous drainage is through the median prosencephalic vein (MPV) of Markowski.[6] The MPV has two segments: the anterior segment regresses while the posterior segment persists and is called the vein of Galen. Normally, there are communications between CAs and the MPV, which should regress after 11 weeks. The formation of certain arteriovenous (AV) shunts due to unexplained reasons leads to the persistence of abnormal communications between the CAs and MPV, forming a dilated venous sac. Thus, as proposed by Raybaud et al, the name “vein of Galen” is a misnomer, as the dilated venous sac is the MPV, not the vein of Galen.[7] [8] According to Lasjaunias, VGAM is classified into two types: viz., mural, where there are direct arterial connections into the wall of the venous aneurysm, and choroidal, where there is an interposition of an arterial network between the multiple feeders and the venous aneurysm[8] ([Fig. 1A, B]). Due to these large shunts, vascular steal phenomenon occurs and according to the degree of shunting, there is an increase in blood returning to the heart and a decrease in perfusion of the normal brain tissue. This leads to cardiac failure and cerebral damage, respectively. The cerebral effects are hydrocephalus, cerebral infarcts, and leukomalacia. Most babies are symptomatic in the neonatal period itself and, if left untreated, have very high morbidity and mortality. However, prenatal diagnosis allows for the delivery of the baby in a tertiary care center, and early intervention would significantly improve clinical and neurodevelopmental outcomes.[9] [10]

Fig. 1 Types of vein of Galen aneurysmal malformation (VGAM) based on Lasjaunias classification. (A) Mural - Characterized by direct, high-flow shunts on the wall of the venous sac. (B) Choroidal - Characterized by multiple fistulas with interposing arterial networks between the feeding vessels and the draining vein. Courtesy: Alfena Raj (Scientific illustrator, University of Massachussets, USA)

In our study, we discuss three prenatally identified VGAMs, their antenatal/postnatal course, management, and varied outcomes, along with a review of updated literature.

Case 1

Thirty-two-year-old second gravida was referred at 37 weeks of gestation for a suspected VGAM in the routine third-trimester US. She was low risk for common aneuploidies in first-trimester screening, and her targeted anomaly scan at 20 weeks was normal.

USG revealed a supratentorial midline, pulsatile anechoic lesion measuring 21 × 21 mm superior to the thalamus. Multiple feeding vessels were seen entering a dilated sac, with the draining vessel emptying into a straight, dilated vessel identified as the straight sinus. Spectral Doppler confirmed turbulent flow with low vascular resistance. Additional findings included bilateral moderate ventriculomegaly (14 mm) and a prominent cisterna magna, without evidence of hemorrhage, necrosis, porencephaly, or cortical malformations ([Figs. 2] [3] [4] [5]). The features were suggestive of VGAM, and the fetal echocardiogram revealed mild cardiomegaly with a cardiothoracic ratio (CTR) of 0.52. Head biometry (biparietal diameter and head circumference) was more than the 99th centile, but the rest of the fetal parameters showed normal growth. There was polyhydramnios with an Amniotic Fluid Index (AFI) of 25 and Dopplers were normal. No other fetal anomalies were noted. Following the diagnosis, the couple received detailed counseling. A prenatal magnetic resonance imaging (MRI) was recommended to confirm the findings and assess for any additional intracranial abnormalities. The limitations of genetic screening at this advanced gestation were discussed. The need for delivery at a tertiary care center was emphasized, along with the importance of comprehensive postnatal evaluation and close follow-up. Multidisciplinary consultations with neonatology, pediatric cardiology, pediatric neurosurgery, and interventional radiology were advised.

Fig. 2 Vein of Galen aneurysmal malformation (VGAM) in two-dimensional (2D) and color Doppler imaging.

Fig. 3 Increased head biometry and bilateral moderate ventriculomegaly.

Fig. 4 Feeder vessels and draining straight sinus of vein of Galen aneurysmal malformation (VGAM).

Fig. 5 Spectral Doppler showing turbulent flow with low vascular resistance.

She went into spontaneous labor at 38 weeks and delivered a male baby weighing 3.82 kg, with an Apgar score of 8. The baby was admitted to the neonatal intensive care unit and was stabilized on continuous positive airway pressure and oxygen and was treated for cardiac failure. Treatment with phenobarbitone and acetazolamide was instituted. Head circumference (HC) was more than the 99th centile, and a cranial bruit was detected. VGAM was confirmed by transfontanellar neurosonogram. Cardiac anatomy and function were normal on echocardiography. Magnetic resonance angiography (MRA) at 1 month showed a VGAM with a maximum diameter of 2.3 cm, dilated straight sinus and confluence of sinuses, and obstructive moderate hydrocephalus. The feeding vessels were identified as from bilateral CAs and venous drainage into the straight sinus and to the posterior superior sagittal sinus ([Figs. 6] [7] [8]). Serial clinical surveillance was done with particular attention to head circumference and cardiovascular performance.

Fig. 6 T1-weighted sagittal image showing flow voids in the region of the vein of Galen aneurysmal malformation (VGAM) and straight sinus (white arrow).

Fig. 7 Magnetic resonance angiography (MRA) showing dilated vein of Galen aneurysmal malformation (VGAM) draining into the straight sinus (white arrow).

Fig. 8 T2-weighted coronal image showing hydrocephalus and thinned out parenchyma.

At 3 months, the baby presented with an increasing head size (> 99th centile), a bulging anterior fontanelle, and a sunset sign. Repeat MRA showed ventricular obstruction with moderate hydrocephalus. Endovascular embolization was planned. Before the procedure, digital subtraction angiography (DSA) was done to evaluate the VGAM angioarchitecture and provide access to endovascular management of the lesion. A left vertebral artery angiogram was done, which showed the VGAM with a large collector sac and feeder vessel from bilateral posterior CAs and venous drainage into the straight sinus and posterior superior sagittal sinus. Endovascular embolization of the collector sac was performed with N-butyl 2-cyanoacrylate gel (80% NBCA). The post-embolization angiogram showed a significant reduction in flow through the malformation with an extremely slow filling of the collector vein ([Figs. 9] and [10]).

Fig. 9 Digital subtraction angiography showing early and late globular filling of vein of Galen aneurysmal malformation (VGAM) (black arrows).

Fig. 10 Posttreatment digital subtraction angiography showing absent filling.

A ventriculoperitoneal shunt was placed 5 days after embolization in view of persistent hydrocephalus. The child was started on antiseizure medication and has been under regular follow-up with a pediatric neurologist, interventional radiologist, rehabilitation therapist, and neurodevelopmental pediatrician, with neurodevelopmental assessments conducted every 6 months.

The child is currently 3 years old, with a stable head circumference, no seizure recurrence, and age-appropriate developmental milestones, demonstrating substantial overall improvement.

Case 2

A 31-year-old primigravida presented with a dichorionic diamniotic (DCDA) twin pregnancy conceived through in vitro fertilization. First-trimester screening revealed a nuchal translucency measurement at the 96th centile in fetus B, with a low-risk result for aneuploidies. The targeted anomaly scan showed no structural abnormalities. At 35 weeks, US demonstrated a 15 × 12 mm midline cystic lesion with internal vascularity near the thalamus in fetus B, suggestive of VGAM. No associated cardiac or cerebral abnormalities were detected. Weekly follow-up scans documented stable cardiovascular status without evidence of hyperdynamic circulation ([Figs. 11] and [12]). This included a search for cardiomegaly, AV valve regurgitation, and changes in the ductus venosus flow velocity waveform.

Fig. 11 Vein of Galen aneurysmal malformation (VGAM) in gray scale (A) and color Doppler imaging (B).

Fig. 12 Spectral Doppler showing turbulent flow with low vascular resistance.

An elective lower segment cesarean section was performed at 37 weeks' gestation, delivering twin male infants weighing 2.8 and 2.7 kg, both with good Apgar scores. Initial transfontanelle neurosonography in fetus B revealed a tubular, dilated anechoic area measuring 15 × 12 × 11 mm in the posterior midline with intense color Doppler flow, consistent with VGAM. As the baby was clinically asymptomatic and showed no signs of cardiac failure, the baby was closely monitored for increasing head circumference and signs of cardiac failure. A repeat neurosonogram at 1 month demonstrated a stable oval cystic midline lesion measuring 14 × 11 × 10 mm caudal to the splenium, with internal vascularity and turbulent flow ([Figs. 13] and [14]).

Fig. 13 Postnatal neurosonography (NSG): Vein of Galen aneurysmal malformation (VGAM) gray scale and color Doppler showing internal vascularity.

Fig. 14 Spectral Doppler showing turbulent flow with low vascular resistance.

The baby remained clinically asymptomatic and was followed up every 3 months. Postnatal MRI at 4 months of age demonstrated a microbleed in the basal ganglia and a chronically thrombosed VGAM. Follow-up MRI at 1 year of age showed complete resolution, with no evidence of VGAM. MRI images are shown in [Fig. 15A to C]. At present, the child is 2 years old, with normal neurodevelopment and ongoing follow-up. This case illustrates the rare occurrence of spontaneous resolution of VGAM.

Fig. 15 (A) Susceptibility-weighted imaging (SWI) showing basal ganglia microbleed (black arrow) suggestive of chronic and thrombosed vein of Galen aneurysmal malformation (VGAM). (B) T2-weighted axial imaging showing thrombosed VGAM (black arrow). (C) T2-weighted sagittal imaging showing a linear hypointense area with no flow void (white arrow) suggestive of thrombosed VGAM.

Case 3

A 27-year-old primigravida at 36 weeks + 5 days of gestation was referred to our center following the antenatal detection of VGAM. Antenatal ultrasonography revealed a supratentorial midline cystic lesion measuring 30 × 15 mm, located superior to the thalamus. Color Doppler demonstrated multiple feeder vessels draining into the lesion, which in turn drained into a straight vessel identified as the straight sinus. Spectral Doppler showed high-velocity, low-resistance flow, consistent with VGAM. Additional findings included mild cardiomegaly (CC/CT ratio: 0.59) and increased umbilical artery resistance.

An elective lower-segment cesarean section was performed at 37 weeks, delivering a male neonate weighing 3 kg. The infant cried at birth but exhibited poor respiratory effort and a heart rate of 100 beats per minute. Echocardiography revealed moderate pulmonary arterial hypertension, a small atrial septal defect, a small patent ductus arteriosus, and normal biventricular function.

Postnatal neurosonography demonstrated a midline posterior fossa cystic structure measuring 19 × 15 × 16 mm, with internal venous and arterial waveforms on color Doppler, likely representing a dilated MPV. Prominent CAs were seen connecting with the venous sac, which drained into a dilated straight sinus—features suggestive of VGAM. On the third postnatal day, the infant underwent endovascular coil embolization, reducing shunted flow by approximately 40 to 50%. However, the neonate succumbed on the third day following the procedure. Prenatal and postnatal ultrasonography images are shown in [Figs. 16] to [18].

Fig. 16 Vein of Galen aneurysmal malformation (VGAM) in gray scale (A) and three-dimensional (3D) power Doppler imaging (B).

Fig. 17 Postnatal neurosonography (NSG): Vein of Galen aneurysmal malformation (VGAM) in gray scale and color Doppler showing internal vascularity.

Fig. 18 Spectral Doppler shows turbulent flow with low vascular resistance.

Discussion

Etiopathogenesis

The underlying cause of VGAM is thought to be ischemia-induced hypoxic injury in the CAs. This injury triggers the release of angiogenic factors, which in turn leads to venodilatation. VGAM generally occurs sporadically and is not linked to any specific chromosomal aneuploidy or syndrome, and familial occurrence is extremely rare. However, recent exome sequencing studies have shown that approximately 10% of VGAM cases result from de novo mutations in the EPH receptor B4 (EPHB4) gene and genes involved in chromatin modification. Other genetic variants implicated in VGAM include mutations in the RAS p21 protein activator 1 (RASA1) gene and the endoglin (ENG) gene.[11] [12] [13] [14]

Classification

Several classification systems have been proposed to define VGAM based on its complexity, type of feeder arteries, location of the fistula, or degree of venous ectasias. The two systems that gained popularity and are being used in current practice are the Lasjaunias and the Yasargil systems, whose morphological features are explained in [Table 1].[15] [16]

Table 1 Classification of VGAM (modified from refs. 15 and 16)

Classification	Morphology
Lasjaunias	Mural - where there are direct, high-flow shunts located within the wall of the venous aneurysm Choroidal - where there is an interposition of an arterial network between the feeders and the venous aneurysm
Yasargil	Type 1 - Arteriovenous (AV) fistula between the posterior cerebral arteries or the pericallosal arteries and the vein of Galen Type II - AV fistula between the thalamoperforating arteries and the vein of Galen Type III - A mix between types I and II Type IV - AV fistula that drain into the vein of Galen and directly dilate it

Abbreviation: VGAM, vein of Galen aneurysmal malformation.

In Lasjaunias classification, VGAMs are classified based on the origin and insertion of the feeder vessels and the clinical presentation. The choroidal type frequently presents with high-output cardiac failure, macrocephaly with loud cranial bruits, and dilated orbital veins due to multiple high-flow fistulas and less restricted outflow. In the mural type of VGAM, there are fewer AV fistulas (AVFs) and more restricted outflow, resulting in greater dilatation of the median vein of the prosencephalon but a lesser chance of high-output cardiac failure. Choroidal type manifests prenatally while mural-type VGAM usually manifests late in infancy as macrocephaly, hydrocephalus, seizures, delayed developmental milestones, and failure to thrive.[16]

Yasargil classified VGAM based on the exact origin of the feeding arteries, and it also differentiates true AVFs, which is type 1 to 3, from AV malformation (AVM), which is type 4 and its subtypes. Based on his classification, VGAMs are a group of AVMs with or without AVFs, and thus, the term vein of Galen aneurysm is slowly being replaced by VGAM.[16]

There is a separate entity called the vein of Galen aneurysmal dilations (VGADs), which represents the enlargement of the true vein of Galen. VGADs occur due to malformations of the pial or dural shunts draining into the true vein of Galen or its tributary, thus causing dilation of the vein of Galen. Another entity is the vein of Galen varix, where there is dilation of the vein of Galen in the absence of an AV shunt. VGADs and vein of Galen varix are separate entities from VGAMs and are not to be confused.[3]

Prenatal Diagnosis

Prenatal diagnosis of VGAM is possible in the late second and early third trimester with two-dimensional ultrasonography supplemented by color Doppler and pulsed Doppler, with a detection rate of 73%.[17] The 3D power Doppler imaging helps in better delineation of anatomic details by removing angle dependence and aliasing irregularities. Though the defect develops in the early first trimester, the aneurysm becomes sonologically apparent, usually in the third trimester.[18] VGAM is a supratentorial midline translucent elongated cyst with active AV flow within the cyst, demonstrated by the color Doppler (Comet tail /Keyhole appearance). In 90% of cases, it is associated with high-output cardiac failure with secondary hydrops.

In a prenatally diagnosed VGAM, a detailed neurosonography should be done including measurement of the orthogonal diameters of VGAM (craniocaudal, anteroposterior, and mediolateral), volume of VGAM (using the ellipsoid formula), noting the presence/absence of other brain abnormalities like straight sinus dilatation, ventriculomegaly, secondary brain lesions like ischemia, leukomalacia, porencephaly, schizencephaly, or cortical malformations. A detailed fetal echocardiography is also warranted to look for evidence of cardiac overload: cardiomegaly, CTR, presence of tricuspid regurgitation, or reversal of blood flow across the aortic isthmus. The presence of tricuspid regurgitation, supraventricular extrasystoles, and tachycardia are associated with adverse outcomes.[19] Differential diagnosis for midline cystic lesions behind the third ventricle includes arachnoid cyst, cavum vergae, porencephalic cyst, choroid papillomas, intracerebral hematomas, and tumors. However, color Doppler would help differentiate VGAM from these lesions. Prenatal MRI is considered the gold standard in diagnosing VGAM and is superior to the conventional Doppler assessment. It helps assess the number and type of arterial pseudo feeders, the exact fistula position, evaluate venous drainage, and identify venous thrombosis. Additionally, fetal MRI can identify significant complications like cardiac failure, fetal hydrops, and brain injury secondary to the hemodynamic alterations of VGAM, thus helping in the prognostication and planning of intervention.[20]

Postnatal diagnosis is typically made using transfontanellar ultrasonography, supplemented by MRA. DSA offers a more detailed assessment of the VGAM angioarchitecture and plays a key role in planning the endovascular management of the malformation.[21]

Prenatal Prognostic Predictors

Prenatal US and MRI parameters have been extensively evaluated to predict adverse outcomes in infants with VGAM. Key US predictors include VGAM volume calculated by the ellipsoid method, dilation of the straight sinus, ventriculomegaly > 10 mm, and cerebral lesions such as porencephalic cysts, leukomalacia, or other signs of ischemic brain injury. Cardiac variables assessed include CTR, presence of tricuspid regurgitation, and reversal of blood flow through the aortic isthmus. In a two-center series of 49 cases, Paladini et al concluded that three prenatal variables were most strongly associated with poor outcomes—major brain lesions leading to neonatal death or late termination, tricuspid regurgitation, and VGAM volume ≥ 20,000 mm³.[22]

Arko et al[23] stratified neonates with VGAM into two prognostic groups:

• Neonates at high risk (NAR): at significant risk for neonatal death or requiring emergency intervention.

• Infantile treatment (IT) group: lower risk, suitable for planned intervention after 1 month of age.

Among several vascular MR imaging parameters assessed—including maximal diameters of the prosencephalic varix, basilar artery, internal carotid arteries (bilaterally), sigmoid sinuses (bilaterally), and the maximal mediolateral diameter of the straight or falcine sinus—the most robust predictor of adverse outcome was the mediolateral width and cross-sectional area of the straight or falcine sinus at its narrowest craniocaudal point. A measurement > 8 mm at this constricted segment reliably distinguished high- from low-risk neonates. Deloison et al, in a retrospective study on the “hidden mortality” of prenatally diagnosed VGAM, reported that the presence of associated cardiac or cerebral anomalies significantly increased the risk of adverse outcomes.[24]

Postnatal Management

A systematic review and meta-analysis (2022) evaluating the outcome of neonates diagnosed with VGAM concluded that, though the incidence of Intra Uterine Demise (IUD) is relatively low (1.5%), approximately 24% succumb during the neonatal period, 29.7% were free from neurological impairment after birth, and 61% had abnormal brain findings on postnatal imaging.[25] This should be considered while counseling the parents regarding the short- and long-term prognosis. High mortality rates were encountered prior to the endovascular treatment era, and morbidity and mortality have reduced significantly with the introduction of surgical and endovascular treatment methods, even with their innate risks.[26] The initial goal is to stabilize the infant's cardiac status, followed by definitive treatment. The commonly followed mode of evaluation of the newborn with VGAM is based on the Bicêtre score developed by Lasjaunias, Ĥopital de Bic ̂etre in France, to decide on the prospective treatment options.[27] [28] This 21-point scale assigns points based on the severity of symptoms and signs related to five systems: cardiac, pulmonary, neurological, hepatic, and renal.

Treatment

Medical management in the neonates is mainly directed toward stabilization of the cardiac status till a definitive surgery is performed. In neonates with acyanotic cardiac failure, medications used are diuretics and/or inotrope therapy, and if pulmonary hypertension is noted, additional treatment with β-agonists, phosphodiesterase inhibitors, digoxin, and prostaglandin infusions is advocated.[29] Historically used treatment methods like open surgery and bilateral internal carotid artery ligation by transtorcular approach have met with adverse outcomes and thus are considered unsafe treatment options. The advent of endovascular embolization essentially changed the outcomes of children diagnosed with VGAM and is the most preferred option today. This treatment method, along with advanced neonatal critical care, has reduced the mortality from 100 to 50%.[30] Though this procedure had been developed in the 1980s, literature is limited to case reports and case series due to its rarity. The preferred treatment time is between 4 and 6 months when the child is considered stable for intervention, thereby ensuring optimal outcomes.

Endovascular embolization aims to occlude the AVF and can be done by two approaches: the transarterial and the transvenous. The transarterial approach is done through the femoral artery, and the transvenous is done through the femoral vein or jugular venous approach. NBCA glue is the embolic material of choice.[28] [31] Detachable microcoils are also an acceptable alternative, though they carry an increased risk of vessel rupture and longer procedure duration. Generally, transarterial embolization is preferred, with the best outcomes seen when there are fewer arterial feeders. However, in cases of multipedicular vein of Galen aneurysms, a transvenous approach is often more effective. When numerous small arterial pedicles are present, a transvenous technique or a combined transvenous–transarterial approach (kissing microcatheter technique) is considered more appropriate.[31] [32] If hydrocephalus is present, it is usually addressed after embolization with ventriculoperitoneal shunting. Surgical intervention is reserved for cases where endovascular treatment fails or in the event of intracranial hemorrhage.

Complications and Outcomes

Overall, post-embolization mortality and complication rates for VGAM are approximately 12% and 35%, respectively.[33] Reported complications include cerebral hemorrhage (37%), cerebral ischemia (6%), hydrocephalus, and nontarget embolization. Over time, clinical outcomes have improved significantly.[34] In 2006, Lasjaunias reported treating 216 children with endovascular glue embolization. Despite or because of the procedure, 23 patients (10.6%) died. Of the 193 survivors, 20 (10.4%) had severe developmental delay, 30 (15.6%) had moderate delay, and 143 (74%) had normal neurological development at follow-up. He concluded that most treated children survive with normal neurodevelopment, emphasizing the importance of careful patient selection and timing.[28] Savage et al, in a systematic review of 35 studies including 307 participants, found that good clinical outcomes were achieved in 68% of cases. They noted that incomplete embolization or early neonatal embolization was associated with higher mortality and poorer outcomes, with an overall all-cause mortality of 16%.[35] Progressive fetal cardiac dysfunction is considered a grave prognostic sign, often indicating that the high-flow lesion may not respond to any treatment.

Spontaneous Resolution of VGAM

There have been reports of thrombosis of VGAM in literature resulting in spontaneous resolution and thus deferring postnatal treatment.[36] [37] [38] This has been identified as more common in mural type and is attributed to the ongoing myointimal proliferation of the VGAM due to turbulent blood flow and increased venous pressure. Other possible mechanisms postulated to lead to spontaneous thrombosis are compression from adjacent hematoma/intra-aneurysmal clot, posthemorrhagic edema, arteriosclerosis of the vessel walls, vascular spasm, and gliosis resulting from microbleeding.[39] Our study also witnessed the spontaneous complete resolution of VGAM in one of the DCDA twins without any postnatal treatment. Research is warranted to understand the complex mechanisms leading to spontaneous thrombosis so that this subgroup is identified to prevent unnecessary interventions with their associated risks.

Role of Prenatal Endovascular Treatment

Though postnatal VGAM management has advanced by strides due to the efficient perinatal intensive care and endovascular treatment methods, there exists a considerable risk for mortality and neurological morbidity associated with postnatal treatment due to the irreversible cardiac and cerebral changes and hence the need for evaluating the role of prenatal endovascular treatment. Orbach et al proposed that performing fetal intervention before the onset of acute postnatal cardiovascular and cerebrovascular stress could reduce both mortality and morbidity. They introduced a novel ultrasound guided transuterine fetal cerebral embolization of VGAM using microcoils, resulting in a normal postnatal outcome without cardiac support and postnatal embolization.[40] Subsequently, Naggara et al successfully managed a case of VGAM through prenatal embolization, using a transuterine transfontanellar approach to insert microcoils into the large AVM. However, this baby needed a postnatal endovascular treatment procedure to occlude the feeder vessels. Postnatally, at 11 months of age, the baby is said to have achieved typical milestones.[41] The common feature in both these cases that prompted the authors to perform the prenatal intervention procedure was the increased width of the fetal falcine sinus > 8 mm, which predicted a very high risk for neonatal decompensation. There have been few anecdotal reports which have been unsuccessful in prenatal endovascular embolization.[42] As there is a lack of standardized protocol regarding the optimal patient selection criteria, the choice of method of endovascular treatment, and their safety profiles, Samaha et al have proposed a global registry where physicians can share their knowledge, techniques, and patient specifics, which will open the doors for an optimal, patient-friendly treatment for VGAM.[43]

Conclusion

Although rare, VGAMs are associated with significant morbidity and mortality. US and MRI play a crucial role in diagnosis, prognostic assessment, and guiding parental counseling, thereby improving management outcomes. Prenatal detection allows for planned delivery at a tertiary care center, where multidisciplinary expertise can provide optimal care. It is important to identify the subset of VGAMs that may resolve spontaneously to avoid unnecessary interventions. Currently, postnatal endovascular treatment performed at 4 to 6 months after initial neonatal stabilization remains the preferred approach. While some prenatal endovascular procedures have shown success, larger prospective studies are needed to establish standardized protocols and guidelines, ensuring the selection of the most appropriate fetal therapy to achieve the best possible neonatal outcomes.

Conflict of Interest

None declared.

Acknowledgment

The authors are grateful to Alfena Raj (Scientific Illustrator, University of Massachusetts, USA) for providing the illustrations for this article.

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Publication History

Article published online:
12 November 2025