This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Not true regarding Dandy Walker cyst ? \nSelect and explain. \nA. Cerebellar Vermis hypoplasia, B. Hydrocephalus, C. Arachnoid Cyst, D. Posterior fossa cyst', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans is \'c\' ie Arachnoid cyst "The Dandy-Walker malformation consist of a cystic expansion of the fouh ventricle in the posterior fossa, which results from a development failure of the roof of the 4th ventricle during embryogenesis. Approximately 90% of pts. have hydrocephalus A significant number of children have associated anomalies including agenesis of the posterior cerebellar vermis and corpus callosum" - Nelson', 'role': 'assistant'}]