Vein of Galen malformations (VGMs) constitute 1% of all intracranial vascular anomalies. They are formed between the 6-11th week of gestation. VGMs involve the presence of one or more arterovenous fistulas directing bloodflow toward a persistent, dilated, proximal part of median prosencephalic vein (MProsV).
They are one of the more frequent arterovenous malformations diagnosed in children pre- and postnatally. Nomenclature is quite imprecise, as this anomaly does not involve the great cerebral vein (vein of Galen), but its embryonic precursor – the median prosencephalic vein (MProsV).
Embryologically in the course of normal development of intracranial vasculature, the MProsV undergoes involution as middle cerebral veins develop. Its proximal fragment vanishes completely, while the distal part is transformed into the vein of Galen. In the presence of VGMs, formation of arterovenous connections with MProsV not only hinders its regression but lead to significant dilatation of the preserved vessel. It appears as a dilated structure in the midline of the brain.
Prognosis in VGMs depends on two main factors. The first one is the severity of heart failure (secondary to right ventricular volume overload) which is directly related to the size of arterovenous shunt and the second is the extent of cerebral ischemia caused by increased venous pressure and so-called cerebral steal.
Treatment of choice involves performing transarterial embolization in the postnatal period and its efficacy depends largely on the size of malformations and developed complications.
Fetal Echo Assessment should involve assessment for the following:
AV valve regurgitation
Ventricular systolic and diastolic function
Cardiac output (large AVMs can cause elevated CO and high output CHF)
Abnormalities in MCA flow (often elevated peak systolic velocities)
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