There is no an agreement about pathogenesis of Chiari Malformations (CM) and CM`s associated with syringomyelia. Dozens of theories are inadequate for explaining some features of CM. Development of them, except Type 1 CM, are congenital; however, Type 1 is not a homogenous group. Conversely, a few evidence suggested that subgroups of type 1 may be an acquired disease. Clarifying of pathogenesis provide improve of the treatment modalities.