Chiari malformation is a condition in which brain tissue in the lower back part of your skull is forced into the spinal canal. Most of the time, this happens because of a structural problem –- a misshaped or smaller-than-normal part of the skull. A Chiari malformation is a problem in which a part of the brain (the cerebellum) at the back of the skull bulges through a normal opening in the skull where it joins the spinal canal. This puts pressure on parts of the brain and spinal cord, and can cause mild to severe symptoms. In most cases, the problem is present at birth (congenital).
Chiari malformations are structural defects in the base of the skull and cerebellum, the part of the brain that controls balance. Normally the cerebellum and parts of the brain stem sit above an opening in the skull that allows the spinal cord to pass through it (called the foramen magnum). Jan 11, · Chiari malformations are structural defects that occur in the cerebellum, the part of the brain that controls coordination and muscle movement. Previous estimates were that malformations occur in about one in every 1, births, but increased use of diagnostic imaging indicates that the disorder may be more common than once thought.