This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Brain , Subject name: Anatomy
Tectal breaking is seen in 
Select and explain. 
A. Dandy - Walker malformation, B. Arnold - Chiari malformation, C. Aqueductal stenosis, D. Third ventricular tumour
B: Arnold - Chiari malformation
Answer: B: Arnold - Chiari malformation 
Explanation: The normal tectum has a rounded or, sometimes, a squared appearance of the colliculi and a sho cranial-caudal length. In the Chiari II malformation, variable degrees of fusion of the colliculi and upward deflection of the tectum result in prominent beaking and elongation of the tectum.Arnold Chiari malformation consists of a downward displacement of the cerebellar tonsils through the foramen magnum resulting in obstructive hydrocephalus.Dandy-Walker malformation is characterized by agenesis or hypoplasia of the cerebellar vermis, cystic dilatation of the fouh ventricle, and enlargement of the posterior fossa.