Is arnold chiari malformation type one a neural tube defect?
The more accepted term is chiari malformation as arnold-chiari is an older term. This type of malformation is not a neural tube defect, but rather an abnormal migration of the cerebellar tonsils below the level of the foramen magnum (chiari type 1).
This defect is attributed to a congenitally small posterior fossa, thus allowing the cerebellar tonsils to migrate downward.
NEURAL TUBE DEFECT