This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diagnosis in obstetrics, Subject name: Gynaecology & Obstetrics
Banana sign on USG is seen in : 
Select and explain. 
A. Arnold Chiari malformation, B. Holoprosencephaly, C. Dandy walker malformation, D. Anencephaly
A: Arnold Chiari malformation
Answer: A: Arnold Chiari malformation 
Explanation: Compression or flattening of the posterior cerebellar surface making a crescentic appearance (banana sign) is seen in open spina bifida and Arnols Chairi's malformation. Reference: Dutta's Textbook of Obstetrics 7th edition page no 647