Contrast enhanced computed tomographic images
A 7-month-old infant presented to the pediatric outpatient services with sudden loss of consciousness. He had an episode of seizure a day before and increasing head size since birth. He had no history of fever, trauma, any skin lesions or family history of neurocutaneous syndromes.
CT contrast study of the head revealed aneurysmally dilated midline venous pouch which showed early filling (in arterial phase) representing dilated vein of Galen measuring 5 x 4.5 cm in maximum diameters. It was seen joining the straight sinus via falcine sinus and eventually draining into the superior sagittal sinus. The straight sinus, transverse sinus and the superior sagittal sinuses were significantly dilated. Also, there was associated partial thrombosis of the confluence of sinuses in the form of incomplete contrast filling. Multiple dilated and tortuous venous channels were noted throughout. Also, a tuft of dilated arterial channels were present in the region of peri-mesencephalic cistern.
Moderate to gross dilation of the supratentorial ventricles was seen s/o non-communicating hydrocephalus.
There was an area of intraparenchymal haemorrhage in the left frontal lobe with cerebral oedema.
Subdural hypodense collection was seen along bilateral cerebral convexities.
Vein of Galen aneurysmal malformations (VGAM) constitute rare congenital vascular malformations; present during infancy with signs of congestive cardiac failure . They are characterized by shunting of arterial flow into an enlarged cerebral vein dorsal to tectum.
Embryologically, VGAM develops after development of circle of Willis, between 6th and 11th weeks of gestation. An arteriovenous connection forms between the primitive choroidal vessels and the median prosencephalic vein. There is abnormal flow through this connection which hampers the normal involution of this embryonic vein. Thus, there is underdevelopment of VOG. As the brain develops further, the shunt persists, with the persistent median vein draining into the sagittal sinus; this is commonly associated with a persistent falcine vein and absence of straight sinus . Anomalous dural sinuses and sinus stenoses are also often seen in relation to VGAM [2,3]. To accommodate the significantly increased blood volume associated with the shunt, alternative pathways of venous drainage typically develop [2,5].
Many classification systems have been described for VGAM (Yasargil classification, Lasjaunias classification, etc). The Lasjaunias system is more commonly used and divides them into two types- choroidal and mural .
The choroidal type are characterised by multiple feeders including thalamoperforating, choroidal and pericallosal arteries. They present earlier (neonate) and commonly results in high output cardiac failure.
The mural type are characterised by fistulae in the subarachnoid space in the wall of the median prosencephalic vein and associated with absence or stenosis of dural sinuses.They present later in life (infant) ;hydrocephalus is a consistent feature.
Ultrasound, Doppler, Computerized tomography (CECT) and Magnetic imaging resonance (MRI) are useful radiological diagnostic tools for vein of Galen malformations . Though MRI provides us with minute details of the malformation and vascular anatomy, CT angiography provides significant information for treatment planning and can be the imaging modality of choice.
Some extremely rare non-developmental syndromes like superior vena cava syndrome (SVCS), thrombosis of the lateral / superior sagittal sinus, internal jugular vein, or Vein of Galen itself can be encountered.
The structure of the malformation decides treatment planning . A ventriculoperitoneal shunt may be required if there is hydrocephalous. Blocking the feeding fistulous arteries reduces the blood flow into the Vein . Open surgery is not a suitable choice since the malformation is highly complicated; endovascular procedures are very useful . Multiple treatment options include catheter guided balloons or coils placement at site of the malformation and radioablation surgery .
Written informed consent for publication has been obtained from the father.
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