This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Congenital CNS malformations, Subject name: Pediatrics
[{'content': 'A neonate presents with features of hea failure. On examination anterior fontanelle was found to be bulging. On auscultation, a cranial bruit was heard. A CT angiography done showed the following: Which vessel is mainly involved in this abnormality? \nSelect and explain. \nA. Median prosencephalic vein, B. Vein of Galen, C. Entire circle of willis, D. Choroid plexus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: - History of features of hea failure, bulging anterior fontanelle, cranial bruit & image given suggests the diagnosis of VEIN OF GALEN MALFORMATION - Vessel involved is - Median prosencephalic vein of markowsky (precursor of vein of Galen) - Onset - 11-13 weeks of gestation', 'role': 'assistant'}]