Vein of Galen aneurysmal malformation

Q: What is Markowski's median prosencephalic vein? show answer

A: Markowski's prosencephalic vein, a precursor to Galen's, undergoes a natural process of regression and persistence. Typically, its anterior portion regresses before birth and forms the internal cerebral veins, while its posterior portion persists as Galen's vein.

Q: What are some characteristics of vein of Galen aneurysmal malformation (VGAM)? show answer

A: VGAM is a congenital vascular malformation characterized by high flow-low resistance shunting of the choroidal or quadrigeminal arteries into an enlarged cerebral vein dorsal to the tectum, Markowski's median prosencephalic vein (MPV). Therefore, the aneurysmal venous sac probably represents Markowski's embryonic median prosencephalic vein, not Galen's. Usually, this embryonic vein involutes by the 11th week of gestation, and its remnants form the vein of Galen.

Q: What are the clinical manifestations of vein of Galen aneurysmal malformations? show answer

A: The presentation varies with the type of malformation. The clinical manifestations are often with features of left-to-right and high-output cardiac failure in the neonatal period. VGAM tends to present during early childhood and is the most common antenatally diagnosed intracranial vascular malformation. Newborns without treatment may develop rapidly deteriorating high-output heart failure and are at risk for severe neurological outcomes. In less severe forms, the disease may manifest later in infancy and childhood, with macrocephaly, hydrocephalus, developmental delay, headaches, and seizures. Low-flow aneurysms may remain undetected into adulthood.

Q: What are the pathology features of Galen aneurysmal malformations? show answer

A: VGAM is a congenital arteriovenous fistula between primitive choroidal and quadrigeminal arteries and the median prosencephalic vein (MPV) - a vein of Markowski, a precursor of the vein of Galen. This arteriovenous fistula, with its abnormal flow through the multiple arterial feeders, retards the involution of the vein of Markowski, leading to a grossly dilated deep cerebral vein, which prevents the formation of the vein of Galen. The MPV drains into the sagittal sinus, usually via a persistent falcine vein. The condition has a genetic background, including RASA1 (RASp21 Protein Activator 1) and EPHB4 (Ephrin type -B receptor 4) anomalies, genes related to vascular development.  

Q: What are the two standard classifications of vein of Galen aneurysmal malformation?   show answer

A: The two standard classifications of vein of Galen aneurysmal malformations are Yasargil classification (types I to IV) and Lasjaunias classification (choroidal and mural types).

Q: What are the antenatal ultrasound characteristics of the vein of Galen's aneurysmal malformation? show answer

A: The dilated median prosencephalic vein (MPV) appears as an anechoic structure in the midline posteriorly and demonstrates prominent flow on Doppler examination. 

Q: How can magnetic resonance imaging (MRI) and MR angiography help diagnose VGAM? show answer

A: MRI and MR angiography are invaluable tools in analyzing these lesions. They depict all the arterial feeders, drainage features, and the anatomy of the fistula point. These methods are also essential for the follow-up of incompletely eliminated lesions.