Presentation
A 22 year old primigravida with 8 months of amenorrhoea was referred for antenatal ultrasound examination. This was her first fetal ultrasound. The fetus corresponded to 31 weeks gestational age by fetal biometry.
Patient Data
Antenatal ultrasound of shows a supratentorial, midline, anechoic, cystic tubular structure which shows evidence of colour uptake and drainage into straight sinus giving the classic appearance of "comet tail" or "keyhole" sign. Feeding vessels are seen from the circle of Willis mainly from the right internal carotid artery and right posterior communicating artery.
Venous drainage is via the straight sinus and then by the transverse and sigmoid sinus and internal jugular veins, mainly through right side. The neck vessels, right internal carotid artery and internal jugular vein are dilated. Superior vena cava is also dilated. High velocity, low resistance flow is noted in the circle of Willis and the aneurysm with high volume venous flow through the draining sinuses and right internal jugular vein. The findings are diagnostic of vein of Galen aneurysmal malformation.
Case Discussion
The findings are diagnostic of vein of Galen aneurysmal malformation. There was no evidence of fetal cardiomegaly. No evidence of fetal skin oedema, pericardial effusion, pleural effusion or ascites to suggest hydrops fetalis which is the most severe complication of this condition.
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