this precursor is actually the dilated channel The vein of Galen is the dilated channel when the arteriovenous connections drain directly into the vein of Galen, which is considered a separate entity A number of different classification schemes have been used to describe these lesions.32,33 VGAMs may consist of a network of vessels or direct arterial feeders into the median prosencephalic vein of Markowski Associations of VGAMs with RASA1 and ACVRL1 gene mutations have been reported.34,35 In addition, a familial association of VGAMs has been described.36 The clinical manifestations are variable and depend on the age at presentation, whether in the neonatal period, infancy, childhood, or adulthood (less common) Due to increasing sophistication of prenatal imaging, fetal presentation is being reported more commonly It is not uncommon for neonates and infants with VGAMs to be misdiagnosed or diagnosed late due to the rarity of this lesion Neonates generally present with the severest form of the disease, with tachypnea, fatigue, poor feeding, and poor growth Systemic organ hypoperfusion can manifest if there is significant runoff in the aorta and can lead to signs of intestinal, renal, or hepatic ischemia In severe cases, cardiorespiratory compromise may ensue if left untreated Neurologic compromise can manifest as seizures, developmental delay, and headaches in patients who present late.37,38 Physical examination reveals a dynamic cardiac precordium and bounding pulses from runoff in the aorta due to the arteriovenous shunting Signs of pulmonary hypertension with a loud pulmonary component of the second heart sound may be present Macrocephaly from hydrocephalus can be present.37,38 A characteristic cranial bruit may be heard on auscultation Chest radiographs reveal cardiomegaly (Fig 50.1) in symptomatic patients, particularly neonates Cardiac chamber enlargement or hypertrophy can be seen on electrocardiograms Transthoracic echocardiography confirms cardiac chamber enlargement, which is usually of the right side of the heart (Fig 50.2) but may progress to enlargement of all chambers and, if left untreated, eventually impacts ventricular function Signs of pulmonary hypertension may be apparent by transthoracic echocardiography Doppler ultrasound is a useful screening tool in neonates and can detect the dilated venous sac (Fig 50.3) and hydrocephalus However, CT and MR with angiography (Fig 50.4) are needed to evaluate for cerebral atrophy, abnormalities in venous drainage pathways (e.g., thromboses), intracranial hemorrhage, and the details of the arteriovenous connections.39,40 Conventional angiography via the carotid arteries is generally reserved for interventional purposes Fetal cardiac diagnostic features of VGAMs by ultrasound consist of an enlarged cardiothoracic ratio, reversal of diastolic flow across the aortic isthmus, and significant tricuspid regurgitation velocity and severity; significant tricuspid regurgitation in the fetus with VGAM is considered a poor prognostic indicator.41 FIG 50.1 Chest radiograph (posterior-anterior projection) of a neonate with a vein of Galen aneurysmal malformation Massive cardiomegaly is noted FIG 50.2 In the same neonate shown in Fig 50.1, this two-dimensional transthoracic echocardiogram in the four-chamber view demonstrates a severely dilated right atrium and right ventricle FIG 50.3 Neonatal head ultrasound or a neonate with a vein of Galen aneurysmal malformation showing the dilated venous channel (the median prosencephalic vein of Markowski) by two-dimensional imaging (A, arrow) and with Doppler color flow mapping (B)