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
Not true regarding Dandy Walker cyst ? 
Select and explain. 
A. Cerebellar Vermis hypoplasia, B. Hydrocephalus, C. Arachnoid Cyst, D. Posterior fossa cyst
C: Arachnoid Cyst
Answer: C: Arachnoid Cyst 
Explanation: 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