63 Vein of Galen Malformations

10.1055/b-0038-162192

63 Vein of Galen Malformations

Fabio Settecase, Vitor M. Pereira, Peter Dirks, and Timo Krings

Abstract

The vein of Galen malformations (VOGM) are defined as a congenital arteriovenous shunt into the precursor of the vein of Galen with an incidence of about 1 out of 25,000 deliveries. A number of studies have shown that the natural history of VOGMs is poor and complicated by congestive heart failure (CHF), hydrocephalus and brain parenchymal injury. Endovascular embolization of VOGM has emerged as standard of care in this patient population; however, long-term outcomes after endovascular embolization as well as predictors of good neurological outcomes are still poorly understood. In the present chapter, we describe management algorithms based on the authors experience in dealing with these cases.

Introduction

Vein of Galen malformations (VOGM) are rare (incidence 1:25000) nonhereditary cerebral arteriovenous (AV) malformations that develop during embryogenesis (6 to 11 weeks gestational age) from the choroidal arterial system. VOGMs represent about 30% of all pediatric vascular malformations. VOGM may present in the prenatal, neonatal, infant, and exceedingly rare in adult periods ( 1 , 2, 3 in algorithm ). With increased use of obstetric ultrasound, diagnosis in utero is becoming more frequent, most often in the third trimester. Treatment of vein of Galen malformations is among the most challenging of all neurovascular procedures.

**Algorithm 63.1** Decision-making algorithm for vein of Galen malformations.

Major controversies in decision making addressed in this chapter include:

Whether or not treatment is indicated.
The ideal timing for treatment.
Open versus endovascular treatment for vein of Galen malformations.

Whether to Treat

Neonate

In some cases, intervention has little or no likelihood of changing or improving the outcome, as prognosis is poor. If there are significant areas of encephalomalacia, diffuse brain volume loss, and/or disruption of subependymal germinal matrix on neonatal magnetic resonance imaging (MRI), there will be a poor outcome related to significant developmental delay and mental retardation irrespective of treatment ( 1 in algorithm ). In these cases, it is reasonable to discuss withholding treatment with family. If the above-mentioned changes can be seen on fetal MRI, or if there is evidence of in utero cardiac or multiorgan failure, therapeutic termination of pregnancy may also be discussed. Neonates presenting with congestive heart failure (CHF) and/or multiorgan failure should receive medical management first. If cardiac failure cannot be controlled by medical measures, embolization of the largest AV shunts should be considered ( 5 in algorithm ).

The Bicetre Neonatal Evaluation Score was developed by Pierre Lasjaunias and his colleagues to help with timing of endovascular management of VAGMs (▶ Table 63.1 ). Treatment is not recommended if the Bicetre score is less than 8/21 (indicative of severe multiorgan failure) due to poor outcomes and high mortality rates observed in this group of patients ( 5 in algorithm ). It is important to convey this information to parents and the medical team. Emergency endovascular intervention is suggested for scores of 8 to 12/21; neonates with a score of more than 12/21 may be managed medically for as long as possible, ideally until 3 or 4 months of age with close monitoring of psychomotor development, and cranial perimeter ( 5 in algorithm). Monthly MRIs may be performed. Delaying treatment until 3 to 4 months of age is advocated by our team as the optimal therapeutic window because the technical challenges and complications of embolization are lessened and the risk of cerebral maturation delay is still low ( 2, 6 in algorithm ). The Bicetre score may vary from day to day depending upon response to medical therapy.

**Table 63.1** Bicetre Score for evaluation of the management of vein of Galen malformations in neonates
Points	Cardiac function	Cerebral function	Respiratory function	Hepatic function	Renal function
5	Normal	Normal	Normal	—	—
4	Overload, no medical treatment	Subclinical, isolated EEG abnormalities	Tachypnea, finishes bottle	—	—
3	Failure, stable with medical treatment	Nonconvulsive intermittent neurologic signs	Tachypnea, does not finish bottle	No hepatomegaly, normal hepatic function	Normal
2	Failure, not stable with medical treatment	Isolated convulsion	Assisted ventilation, normal saturation Fio₂ < 0.25	Hepatomegaly, normal hepatic function	Transient anuria
1	Ventilation necessary	Seizures	Assisted ventilation, normal saturation Fio₂ > 0.25	Moderate or transient hepatic insufficiency	Unstable diuresis with treatment
0	Resistant to medical therapy	Permanent neurological damage	Assisted ventilation, desaturation	Abnormal coagulation elevated enzymes	Anuria

Infant

The goal of VOGM treatment in infants and children is to maintain hydrovenous equilibrium (see Pathophysiology section) to ensure normal brain development while excluding the lesion. Indications for endovascular embolization in infants include a neonate initially presenting with a Bicetre score greater than 12 who has reached 3 to 4 months of age; rapidly increasing macrocephaly based on monthly head circumference measurements, new diagnosis of VOGM with clinical manifestations; known VOGM with new hydrocephalus or MRI signs of increased intraventricular pressure; new brain MRI abnormalities related to brain injury, progressive venous stenosis, worsening cardiac failure, failure to thrive, or development delay ( 2, 6 in algorithm ). Evidence of severe brain damage or atrophy on MRI (usually seen in cases of delayed referrals) may preclude treatment with embolization.

Child

Urgent endovascular embolization should be undertaken if there is increasing macrocephaly, hydrocephalus or other MRI signs of increased intraventricular pressure, new brain MRI abnormalities related to brain injury, evidence of pial venous reflux, acute symptoms, or development delay ( 3, 7, 9 in algorithm ). In this age group, these changes are often due to presence of jugular venous stenosis or occlusion from long-standing increased dural venous pressures.

Older Children and Adults

Presentation or delayed diagnosis in this age group is characterized by subacute and chronic symptoms, such as failure to thrive, bone hypertrophy, mental retardation, seizures, cerebral calcifications, and psychiatric disorders. These symptoms cannot be reversed with treatment, as the optimal therapeutic window has passed.

Anatomical Considerations

Arterial supply to VOGM is typically from the choroidal arteries (posterior and anterior), the distal pericallosal artery (through a persistent limbic arch), circumflex (aka tectal or circumferential) arteries, splenial arteries, thalamoperforators, also known as, subependymal arteries (which are secondarily activated, not primarily involved, and will regress if the choroidal arterial supply is embolized), and dural branches of superior cerebellar arteries.

The venous drainage of VOGM is unique to this disease. Venous drainage of vein of Galen malformations is actually not the vein of Galen (which develops at 10 weeks gestational age) but its precursor, the median prosencephalic vein of Markowski (i.e., the median vein of the prosencephalon or MVP). In embryonic development, the choroidal veins initially drain into this transient vein. The presence of an AV shunt hinders however its regression. Persistence of fetal patterns of venous drainage, such as a persistent falcine sinus with straight sinus occlusion or hypoplasia, an occipital sinus, or a marginal sinus, is also usually seen. Whether communications exist between the MVP and the deep venous system is controversial. If present, these communications cannot be seen on angiography. Due to the presence of the AV shunt, the deep venous drainage of the brain needs alternate pathways to drain either through the lateral perimesencephalic vein or median parietal veins.

Pathophysiology/Classification

Two main angioarchitecture patterns for VOGM exist, mural and choroidal types (▶ Fig. 63.1 ), although many are of a mixed type, combining aspects of both. In the mural type (▶ Fig. 63.1a , no nidus is seen, and there will be one or many direct AV (fistulous) shunts into the MVP venous pouch. Mural type VGAM is often better tolerated and thus present in infants with no cardiac symptoms and higher clinical scores, unless multiple large shunts are present. In choroidal type (▶ Fig. 63.1b and ▶ Fig. 63.2 ) (56-76% of all VOGM), a network of abnormal vessels between the feeding arteries and the venous pouch is present. Neonates presenting with heart failure more often have the choroidal type. In neonates, heart failure may lead to respiratory failure, fluid overload, renal failure, liver failure, and a coagulopathy. Neonates with VOGM do not present with intracranial hemorrhage. Significant AV shunting into a VOGM can also cause arterial steal from normal brain. As a consequence, arterial oxygenation of cerebral tissue is impaired and this can eventually lead to melting brain syndrome (see Imaging section).

**Fig. 63.1** Illustrations depicting the two different types of vein of Galen malformation. **(a)** mural type and **(b)** choroidal type. (Used with permission from the Barrow Neurological Institute.)

**Fig. 63.2** This male baby was born with severe cardiac insufficiency and pulmonary hypertension and transferred to our institution at his 6th day of life for advanced cardiac and neurointerventional care. He was hemodynamically unstable despite the best medical treatment since birth. Treatment was carried out on his 7th day of life with the plan being to reduce the flow on the VGAM and consequently reduce the cardiac overload. **(a,b)** MRI T2 sequences, axial views. Note the choroidal vessels within the perimesencephalic cisterns and the venous pouch protruding inside the 3rd ventricle. An emergency procedure was performed **(c–f) (c)** Rt ICA DSA lateral view. **(d)** Left vertebral DSA injection lateral view: multiple choroidal feeders are seen being connected to the inferior portion of the venous pouch and there is a large venous dilatation draining into a remnant falcine sinus. **(e)** Microcatheter injection in one of the posterior choroidal fistulous components of this complex VGAM. **(f)** AP non subtracted view—Glue cast after embolization. Blood pressure improved considerably during the procedure. Patient had a good clinical evolution and became hemodynamically stable. The second and third sessions were scheduled when he was 3 months old. **(g–j) (g)** Left vertebral AP view. **(h)** DSA AP view—Glue injection of a posterior choroidal fistulous component of the vascular malformation. Note the “mushroom” cast with the stem corresponding to the arterial portion of the fistula and the cap within the venous portion. **(i)** Right ICA demonstrating a residual retrograde pericallosal feeder, which was secondarily recruited into the VGAM. **(j)** Glue cast after embolization of the pericallosal feeder demonstrating the expected distal arterial and proximal venous deposition of glue. **(k,l)** MRI T2 sequences after three embolization sessions showing occlusion of most of the fistulous connections and reduction of the size of the venous pouch. The patient reached all developmental milestones on last follow-up, is no longer on cardiac medication, and remained neurologically intact.

If a neonate with a VOGM survives without arterial steal or cardiac failure, hydrodynamic disorders (macrocephaly, hydrocephalus) are typically seen as a presenting symptom in infants. Hydrodynamic disorders result from increased pressure in the venous system. As CSF is absorbed via medullary veins, a high venous pressure in the setting of pronounced AV shunting will lead to impairment of CSF absorption. There is little effect on the brain itself as long as the sutures are open and the brain can grow. As a result, macrocephaly may not necessarily progress to hydrocephalus. If the sutures stop growing or medullary vein reabsorption decreases or venous system compliance fails, hydrocephalus and intracranial hypertension ensue. Clinical manifestations include irritability, altered level of consciousness, changes in head circumference, decrease in brain volume with increase in fluid spaces, and developmental delay. Ventricular shunting does not treat the underlying cause of the hydrocephalus and may lead to new neurologic deficits, seizures, hemorrhages, subdural effusions or increase in the venous pouch. Spontaneous stabilization of increasing head circumference can occur with cavernous sinus capture of the Sylvian veins, which occurs after 3 months of age. With cavernous capture, brain venous drainage (and CSF absorption) improves via superior and deep middle cerebral veins and sometimes results in increased prominence of facial veins).

High pressure in venous sinuses can result in intimal proliferation at the jugular bulb, incomplete development of the sigmoid sinuses, and abnormal skull base development, leading to varying degrees of jugular bulb stenosis and dysmaturation. Dysmaturation of the jugular bulb involves bony stenosis of the jugular foramen, which may progress to jugular bulb occlusion. Although jugular bulb stenosis reduces cardiac congestion, it increases cerebral venous congestion. Secondary effects of jugular bulb stenosis and occlusion include venous reflux, which in turn can lead to hydrodynamic disorders, neurological deficits, seizures, prominence of facial veins, and epistaxis (related to facial venous congestion), tonsillar herniation related to infratentorial venous congestion, as well as intracranial hemorrhage due to pial venous reflux.

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