Chiari malformation is a congenital anomaly that is divided into four types depending on the severity of the condition. Chiari malformation type II is also known as Arnold Chiari malformation, and is one of the most common types.

Chiari malformation is divided into four types: I, II, II, IV. Of which, Chiari malformation type I is common and has a milder degree than the other types.

Arnold Chiari syndrome forms during fetal development, it is a congenital malformation that causes excessive distortion of the brain due to mismatch in size or deformation of a certain area of the skull.