Chiari malformations. Type i is associated with a portion of the cerebellum called the tonsils, downwardly displaced through the foramen magnum at the base of the skull. Most are asymptomatic. Type ii is usually associated with a failure of the spinal cord to close and is often associated with hydrocephalus.
Several things. Type 1 chiari is usually found in later life and the cerebellar tonsils descend below the skull. Type 2 is usually found early on in life and associated with lower back defects in the spinal canal. The brain stem is also descended in type 2 chiaris and hence these patients are more symptomatic than type 1 patients. Please ask your md for more.