Case study 142 - Chiari malformation type one The month of September is Chiari Malformation Awareness Month. Chiari Malformation is a serious neurological disorder affecting more than 300,000 people in the United States. Chiari Malformation is a congenital malformation in which the bottom of the brain, known as the cerebellum, is crowded in the skull cavity and forces the lower tips of the cerebellar hemispheres, or tonsils, into the hole in the bottom of the skull, or foramen magnum. #sundaycas