Vein of Galen Aneurysmal Malformation (VGAM) Fetal MRI

Step-by-step decision

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Full pathway

1. [Decision] Diagnosis + heart failure/brain injury prognostic markers
   Diagnosis confirmation + heart failure/brain injury prognostic markers (fetal MRI)? (VGAM = a choroidal-type AVM (6–11 weeks), arteriovenous fistulas draining into the median prosencephalic vein of Markowski (precursor of the vein of Galen), causing a dilated midline venous sac. US: midline anechoic/cystic mass (behind the third ventricle, below the CC/CSP) + color Doppler high-flow turbulence. Fetal MRI: a T2 flow-void midline tubular/cystic structure (behind the third ventricle) + drainage into a dilated straight/falcine sinus + surrounding flow voids.)
   • Confirmed VGAM, no heart failure/brain injury, normal cardiac function → Currently stable · serial monitoring
   • High-output heart failure (cardiomegaly, jugular/SVC dilation, edema) or brain injury (melting brain/hydrocephalus) → Heart failure/brain injury · poor prognosis
2. [End] Currently stable · serial monitoring
   Confirmed VGAM, no high-output heart failure or brain injury yet: low intrauterine systemic resistance may compensate temporarily; serial fetal MRI/ultrasound monitoring of cardiac function, venous sac size, brain parenchyma (ischemia/hemorrhage), ventricles; multidisciplinary prenatal counselling, plan delivery at a center with pediatric neurointervention capability, postnatal staged embolization.
3. [End] Heart failure/brain injury · poor prognosis
   High-output heart failure (cardiomegaly, jugular/SVC dilation, edema/ascites) or brain injury (melting brain parenchymal destruction/hemorrhage, hydrocephalus): indicates high flow, poor prognosis; fetal MRI to assess the extent of brain injury (key to prognosis); multidisciplinary counselling (postnatal Bicetre score guides embolization timing); severe brain injury/multi-organ failure has a very poor prognosis.

Source guidelines & references

• Vein of Galen aneurysmal malformation fetal MRI prognostic markers (heart failure/brain injury; AJOG 2020)

This pathway is our own synthesis of the decision logic in the guidelines above (not the guideline verbatim); thresholds and workflows change as guidelines update — in practice follow the latest guideline, your institution's protocol and the individual patient.

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