A 5-month-old boy has a history of cardiac failure since birth, which has been controlled sufficiently with diuretics, and he is feeding well orally. MRI is performed. His psychomotor development is normal on follow-up visits, and he is now scheduled for angiography and embolization. His physical and neurologic examination findings at admission are normal.

Fig. 56.1 Coronal T2-weighted MRI reveals a midline dilated vascular structure at the vein of Galen region.

Fig. 56.2 DSA. Left VA angiogram in (A) AP and (B) lateral views. (C) DSA after embolization demonstrates a “mushroom” configuration of the glue cast with minimal penetration into the proximal venous pouch. (D) On left VA angiogram in lateral view after embolization, improved visualization of the posterior fossa veins suggests regression of venous congestion.

Mural type of vein of Galen aneurysmal malformation Treatment

• Standard 4F access (puncture needle, 4F vascular sheath)
  
• Standard 4F multipurpose catheter (Cook Medical, Bloomington, IN) with continuous slow drip and a 0.035-in hydrophilic guidewire (Terumo, Somerset, NJ)
  
• A 0.018-in flow-directed microcatheter (BALTACCI; Balt International, Montmorency, France) with a steam-shaped 90-degree curve
  
• A 10% glucose solution
  
• Histoacryl/Lipiodol/tantalum powder (2 mL/0.1 mL/1 vial)
  
• Contrast material (maximum number of milliliters, 4 × body weight in kilograms)

Vein of Galen aneurysmal malformations are arteriovenous malformations of the choroidal system that develop in the early embryonic stage. They account for ~30% of all vascular malformations in the pediatric population. Cardiac failure, the most common presentation in neonates, may progress to multiple-organ failure if left untreated and is probably related to the lower cardiovascular volume of these patients. A clinical presentation with hydrodynamic disorders, such as hydrocephalus and macrocrania, is more commonly seen in older infants. Only rarely is this disorder diagnosed in older children, who are more likely to present with neurologic symptoms such as seizures, neurologic deficits, and even intracranial hemorrhage. These cases are associated with a poor outcome, which is likely related to the degree of brain damage caused by the vein of Galen aneurysmal malformation. Certain angioarchitectural characteristics are specific for vein of Galen aneurysmal malformations. The arterial supply always involves the choroidal arteries, including the anterior choroidal artery, posterior choroidal artery, and subforniceal artery (anterior cerebral artery [ACA] branch). The subependymal arteries and limbic arterial arch (between the PCA and ACA branches) constitute the remainder of the supply. Secondary supply from transcerebral branches of the middle cerebral artery (MCA) typically represents sump effect and arterial steal. Two types of nidi are seen in vein of Galen aneurysmal malformations: a mural type, consisting of direct arteriovenous fistulae within the wall of the median vein of the prosencephalon, and a choroidal type, which corresponds to a more primitive condition. In the choroidal type, a network is interposed between the nidus and the opening into the large venous pouch. Venous drainage is toward the dilated median vein of the prosencephalon, which is the forerunner of the vein of Galen. Although it has been previously reported that no communication between this vein and the deep venous system exists, many case reports have actually documented a connection, typically at the posterior aspect of the dilated venous segment. Several embryonic sinuses often persist in vein of Galen aneurysmal malformations, including a falcine sinus, which may occur with absence of the straight sinus and of the medial occipital and marginal sinuses.

• A dilated median vein of the prosencephalon is seen as an anechoic tubular midline structure located superior to the cerebellum. Increased flow on color Doppler images helps to confirm the diagnosis.
  
• Prenatal ultrasound is most sensitive for the detection of vein of Galen aneurysmal malformations after the 26th week of gestation.

• MRI is the best imaging modality for the evaluation of vein of Galen aneurysmal malformations and can also be done prenatally to assess the brain parenchyma.
  
• A dilated midline venous pouch, representing a dilated median vein of the prosencephalon, can be seen on CT scan and as a flow-void structure on MRI.
  
• Parenchymal changes are best seen on FLAIR images and T2-weighted MR sequences and can be classified as focal encephalomalacia or diffuse loss of brain volume.
  
• Focal encephalomalacia is more likely related to the presence of arterial steal, which is a result of the high-flow sump effect of the vein of Galen aneurysmal malformation. It is characterized by leptomeningeal collateralization of the cortical branches of the MCA or the ACA to the PCA territories, further contributing to the arteriovenous shunt of the vein of Galen aneurysmal malformation, and is best seen on contrast-enhanced CT or as flow-void structures on T2-weighted MRI.
  
• Diffuse loss of brain volume is usually associated with hydrocephalus and may be reversible following treatment.
  
• Hydrodynamic disorders caused by vein of Galen aneurysmal malformations include macrocrania, hydrocephalus, and venous congestion.
  
• Acute venous congestion can result in brain edema, seen as hypodensity on CT or T2 hyperintensity on MRI, and in tonsillar prolapse infratentorially. Chronic venous congestion usually results in parenchymal calcifications, which are better seen on unenhanced CT than on gradient-echo MRI.
  
• Diffusion-weighted abnormalities tend to indicate a poor prognosis, and therapeutic abstention may be chosen if the diffusion-weighted imaging changes are rapidly progressive.

• Early filling of the dilated median vein of the prosencephalon with enlargement of the arterial feeders can be seen on both CTA and MRA. These techniques are able to determine whether a mural or choroidal type of shunt is present.
  
• CTV and MRV may be helpful in the evaluation of the venous outflow restrictions, usually caused by dysmaturation or stenosis of the jugular bulb, and to evaluate whether cavernous capture has taken place (bulging of the cavernous sinuses).

• Angiography is the gold standard for the detailed evaluation of the angioarchitecture of a vein of Galen aneurysmal malformation and must be done within the same session as the endovascular treatment to avoid multiple punctures to the femoral arteries.
  
• In neonates, the restricted amount of contrast (maximum, 4 mL/kg) is a major limitation for a complete study.
  
• One VA and one ICA are evaluated to identify the major feeder and determine how the normal brain drains.

• The therapeutic strategy is to ensure normal development; therefore, the cardiac overload and venous congestion must be reduced, and oral feeding has to be ensured.
  
• The initial management of a neonate with a vein of Galen aneurysmal malformation and congestive heart failure consists of medical stabilization of the heart failure, typically with digoxin (increase inotropy), diuretics (decrease preload), dopamine (increase cardiac output), mechanical ventilation (less oxygen needed), or inhaled nitric oxide. These therapies are aimed at allowing the baby to feed orally so that he or she gains weight. If medical therapies fail, endovascular therapies are indicated.
  
• The best position for the baby is a 20- or 30-degree head-up position in the bed to optimize venous drainage without kinking of the jugular veins.

• Surgical removal of the lesion is no longer advised because of the hemodynamic instability of these patients and the deep location of the lesion, which result in a high mortality rate.
  
• Ventricular shunting should be avoided because it does not treat the hydrovenous disorder responsible for the ventricular enlargement. In fact, ventricular shunting frequently worsens the size of a vein of Galen aneurysmal malformation and leads to subcortical calcifications.
  
• Surgery is reserved for the evacuation of intracranial hematomas in rare cases that bleed and the treatment of severe hydrocephalus that does not decrease after embolization.

• Transarterial embolization is the treatment of choice for vein of Galen aneurysmal malformations, and the optimal timing of embolization is at 4 to 5 months of age; this waiting period is not long enough for permanent brain damage to develop yet offers enough benefit concerning arterial access and contrast limitation problems. More urgent treatment may be considered for patients with a Bicétreneonatal score of 8 to 11, deteriorating or severe congestive heart failure, evidence of arterial steal, and/or progressive occlusion of the venous outflow without permanent brain damage on MRI or CT.
  
• A femoral arterial access is routinely used in our practice; however, in a newborn up to 3 days of age, an umbilical artery access may be used.
  
• In the authors’ experience, pure glue (2 mL of Histoacryl/0.1 mL of Lipiodol with tantalum powder) is the preferred embolic material for high-flow, muraltype fistulae. The microcatheter is placed against the wall of the feeding artery, and the pure glue is rapidly injected to produce a “mushroom” appearance of the glue cast, which minimally penetrates the proximal venous pouch. A more diluted concentration of glue or other liquid embolic materials, such as Onyx, may be considered with the choroidal type of nidi but tend to be associated with prolonged injection times and radiation exposure, which is a strong concern in pediatric patients.
  
• Multiple arterial feeders are often encountered; the largest are usually embolized first to allow normal cardiac and neurologic development. Multiple sessions may be required to achieve the desired clinical effect. The goal of the treatment is a child who can develop normally rather than an impaired child who is cured. Progressive thrombosis of a vein of Galen aneurysmal malformation is not infrequent, even after partial treatment with some glue penetration into the venous pouch.
  
• A transvenous route may also be used but carries a higher risk for complications, including venous perforation and occlusion of the deep venous drainage with fatal brain hemorrhage. It has also proved to be much less efficient than transarterial glue embolization in reversing high-output cardiac failure.

• Puncture site complications with thrombosis or dissection of the artery and, in the worst case scenario, loss of the lower limb
  
• Pulmonary emboli
  
• Migration of the embolic agent into the posterior aspect of the dilated venous pouch, causing occlusion of the deep venous drainage with subsequent venous infarctions/hemorrhage
  
• Perforation of the arterial feeders
  
• Re flux of the glue into normal arteries, resulting in ischemic stroke

Before the advent of embolization, patients with vein of Galen aneurysmal malformations had a dismal prognosis. In the early surgical series, the mortality rate was 99 to 100%. Outcomes improved with advances in endovascular embolization techniques and neonatal care, which led to a 0 to 50% mortality rate (with a 28–68% overall poor outcome). Although the outcome of patients has been improving over the years, the overall outcome was still considered poor in up to 50% of patients in the larger series published by Lasjaunias et al. Approximately 10 to 20% of patients with vein of Galen aneurysmal malformations were considered to be in too poor condition to be treated or expired before treatment. In the largest series reported so far by Lasjaunias et al, in 2006, ~60% of the 233 patients who were treated with endovascular embolization had a good outcome. In their total cohort of 317 patients, spontaneous thrombosis of the shunt occurred in 2.5% (8/317). In a recent series of the Toronto experience by Geibprasert et al, 47% of the patients treated had a good outcome, and 5 of 6 patients in a subgroup of carefully selected patients had a good outcome with conservative management and close follow-up. The criteria for the selection of these patients were as follows: (1) a high neonatal score (> 17); (2) clinical symptoms of only mild congestive heart failure well controlled with medication and no neurologic symptoms; (3) imaging findings indicating no parenchymal loss, calcifications, hydrocephalus, tonsillar herniation, or evidence of arterial steal; and (4) angioarchitectural findings of low-flow shunts (i.e., two or fewer enlarged arterial feeder groups, lack of deep venous drainage, lack of jugular bulb stenosis). The management of patients with a vein of Galen aneurysmal malformation remains challenging and should be based on an assessment of the individual patient and the operator’s personal experience.

• Vein of Galen aneurysmal malformations are choroidal arteriovenous malformations that develop during the early embryonic stage and drain into the median vein of the prosencephalon, which is the precursor of the vein of Galen.
  
• Factors associated with a poor outcome are the following: neurologic symptoms at presentation, a Bicétre neonatal score of less than 12 of 21, a very poor score of less than 2 of 5 in one (or more) categories, focal parenchymal changes, calcifications, tonsillar herniation, arterial steal, and multiple arterial feeders.
  
• The management decision is challenging and must be made on an individual basis. The optimal treatment time is at 4 to 5 months of age; however, urgent treatment should be considered for those who have deteriorating congestive heart failure or evidence of arterial steal or progressive occlusion of the venous outflow without evidence of permanent brain damage on CT or MRI.

Alvarez H, Garcia Monaco R, Rodesch G, Sachet M, Krings T, Lasjaunias P. Vein of Galen aneurysmal malformations. Neuroimaging Clin N Am 2007;17(2):189–206

Geibprasert S, Krings T, Armstrong D, Terbrugge KG, Raybaud CA. Predicting factors for the follow-up outcome and management decisions in vein of Galen aneurysmal malformations. Childs Nerv Syst 2010;26(1):35–46

Lasjaunias PL, Berenstein A, terBrugge KG. Surgical Neuroangiography. Vol 3: Clinical and Interventional Aspects in Children. 2nd ed. New York, NY: Springer; 2006

Lasjaunias PL, Chng SM, Sachet M, Alvarez H, Rodesch G, Garcia-Monaco R. The management of vein of Galen aneurysmal malformations. Neurosurgery 2006;59(5 Suppl 3):S184–S194, discussion S3–S13

A 7-year-old previously healthy boy has had significant headaches over the past 2 weeks. His parents confirm that he has never had any headaches before. Outside CT has demonstrated dilated vessels, and he is referred to our institution for further workup.

Fig. 57.1 (A–C)