Tectal breaking is seen in
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.
Dandy - Walker malformation
Arnold - Chiari malformation
Aqueductal stenosis
Third ventricular tumour
Brain 