Vein of Galen Malformations

Fig. 26.1 A choroidal vein of Galen aneurysmal malformation demonstrating the anterior nidal network of arterial feeders is shown by artist depiction (a) and after vertebral angiography (b).

Fig. 26.2 A mural vein of Galen aneurysmal malformation demonstrating direct arteriovenous fistulas to the wall of the median prosencephalic vein is shown by artist (a) depiction and after angiography (b).

VGAMs are distinct from anomalies such as vein of Galen aneurysmal dilation or vein of Galen varix that simply manifest with dilation of the true vein of Galen. VGAMs are characterized by arteriovenous shunting into a persistent median prosencephalic vein of Markowski, the embryologic precursor of the vein of Galen. This distinction between VGAM and vein of Galen aneurysmal dilation or varix is critical because there are implications for treatment. The median prosencephalic vein is an embryological remnant that continues to exist because of pathological arteriovenous shunting, and thus it can often be occluded without impairment of venous drainage in the surrounding brain. This is not generally true for the vein of Galen. The vein of Galen in a vein of Galen aneurysmal dilation or varix typically retains the essential role of draining the deep cerebral venous system and should not be occluded.

26.2 Patient Selection

26.2.1 Clinical Presentation

The presentation of patients with VGAMs is diverse and contingent upon lesion angioarchitecture, the presence of comorbidities and the age of the patient. Early, fulminant presentations suggest higher degrees of arteriovenous shunting and, as a result, portend more severe morbidity and increased mortality. ³^, ⁴ In neonates, the initial presentation is frequently congestive heart failure with cyanosis, respiratory distress, and electrocardiographic changes ( ▶ Fig. 26.3). Up to 95% of patients with antenatally diagnosed VGAM presented with systemic cardiac symptoms at birth. Severe pulmonary hypertension, systemic ischemia, and prenatal hydrops may be present. Such presentations may be further complicated by diastolic flow reversal in the descending aorta particularly in patients with right to left cardiac shunting due to a patent foramen ovale or ductus arteriosus. ⁵

Fig. 26.3 This newborn presented with evidence of congestive heart failure. Chest X-ray demonstrates cardiomegaly and pulmonary congestion (a). Noncontrast head computed tomography shows the presence of a vein of Galen aneurysmal malformation without significant hydrocephalus. (b)

The presentation of VGAMs in infants and young children are usually with lesser degrees of arteriovenous shunting and thus a more insidious clinical course. Hydrocephalus and increased head circumference, headaches, seizures, and developmental delay are commonly seen. Focal neurologic signs and symptoms or psychomotor delay due to vascular steal may also be seen in this age group. ⁵ Findings may include evidence of incipient heart failure, but more commonly, signs such as progressively increasing head circumference, dilated scalp and facial veins, and failure to achieve appropriate developmental milestones are noted. ⁴ Hydrocephalus may develop secondary to obstruction of the cerebral aqueduct, hemorrhage, venous sinus occlusion, or intracranial venous hypertension. Cranial bruits, proptosis, and recurrent epistaxis may also be observed in this population. ⁵

26.2.2 Preoperative Evaluation

The angioarchitecture of VGAMs can be complex. Several classification schemes have been reported. An understanding of the detailed angioarchitecture of a VGAM under consideration for treatment is critical for determining the optimal therapeutic approach. The historically interesting VGAM classifications by Litvak and, later, Yasargil have been simplified by Lasjaunias. ⁶

Lasjaunias classified VGAMs into choroidal and mural subtypes. ³^, ⁷^, ⁸ Choroidal VGAMs are characterized by arterial feeders from choroidal vessels forming a nidal network draining into the anterior aspect of the median prosencephalic vein ( ▶ Fig. 26.1). The multiple high-flow fistulas present in choroidal VGAMs typically result in early symptomatic expression during the neonatal period. Mural VGAMs are characterized by at least one direct arteriovenous fistula within the wall of the median prosencephalic vein ( ▶ Fig. 26.2). ⁸ The site of fistulous drainage is often at the inferolateral wall of this primitive vein. Mural VGAM tend to have lower flow through the fistulous connection and thus frequently present outside of the neonatal period with relatively milder but insidious symptoms. ⁹

Not all VGAMs fit nicely into either Lasjaunias choroidal or mural subtypes. Indeed, it is increasingly recognized that intermediate subtypes with features of both choroidal and mural VGAMs exist. ³

Effective management of VGAMs necessitates a multidisciplinary approach involving pediatric medical, surgical, and interventional specialists. Emergent intervention is not always required, allowing time for preoperative optimization of cardiac and pulmonary status in many cases. However, some patients in high-output cardiac failure may need to be treated immediately. Diagnostic workup should begin with a physical examination including weight, head circumference, assessment of peripheral perfusion, neurological testing, and cardiopulmonary evaluation. Hepatic and renal function should be assessed particularly in the setting of cardiac insufficiency and systemic ischemia. An echocardiogram should be performed either antenatally when a prenatal diagnosis is made or on the first day of life. Documentation of baseline cardiac function and identification of associated congenital cardiac malformations is of critical importance in this patient population. Electrocardiography should be performed to identify evidence of myocardial ischemia and any conduction abnormalities. ⁹^, ¹⁰ When indicated, respiratory support should be initiated with supportive oxygen therapy via nasal cannula, CPAP/BiPAP, or intubation as appropriate. Digitalis derivatives and/or diuretic therapy may have utility in the setting of volume overload. ¹^, ⁹

Radiographic evaluation should include noninvasive modalities when possible. In neonates transfontanelle ultrasound can be performed rapidly at the bedside to evaluate for hemorrhage, hydrocephalus, and gross VGAM characterization ( ▶ Fig. 26.4). Magnetic resonance imaging and angiography (MRI/A) provide abundant information about associated structural changes to the brain parenchyma including atrophy, infarcts, calcifications, ventricular size, and the angioarchitecture of the malformation ( ▶ Fig. 26.5 and ▶ Fig. 26.6). In older children and adults computed tomography (CT) may be employed as a screening tool and to rapidly diagnose associated subarachnoid or parenchymal hemorrhage. CT angiography (CTA) provides greater spatial resolution and shorter acquisition time than MRA with the downside of additional radiation exposure. ¹ In patients with depressed mental status without acute hydrocephalus or hemorrhage, electroencephalography serves as a useful diagnostic tool to rule out status epilepticus and for localization of seizure foci. Catheter angiography remains the gold standard for obtaining detailed anatomic characterization of VGAMs and is typically used once a decision has been made to proceed with endovascular intervention.

Fig. 26.4 Transfontanelle color Doppler ultrasound indicates the presence of a dilated midline venous collector in the region of the normal vein of Galen (a). Subsequent magnetic resonance venography confirms the structure to be a vein of Galen aneurysmal malformation (b).

Fig. 26.5 This adult patient with a partially treated vein of Galen aneurysmal malformation during infancy presented 20 years later with epilepsy, hemiparesis, and dementia. Chronic brain parenchymal changes including atrophy, gliosis, and dysplastic vascular proliferation are evident on magnetic resonance imaging and angiography (a–c). Interestingly, the patient showed dramatic cognitive improvement after further treatment and was able to find employment.

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