are structural defects in the cerebellum, the part of the brain that controls balance. When the indented bony space at the lower rear of the skull is smaller than normal, the cerebellum and brainstem can be pushed downward. The resulting pressure on the cerebellum can block the flow of cerebrospinal fluid (the liquid that surrounds and protects the brain and spinal cord) and can cause a range of symptoms including dizziness, muscle weakness, numbness, vision problems, headache, and problems with balance and coordination. Treatment may require surgery. Many patients with the more severe types of Chiari malformations who undergo surgery see a reduction in their symptoms and/or prolonged periods of relative stability, however paralysis is generally permanent despite surgery.
There are four types of Chiari malformations. The types tend to correspond with the degree of severity, with type 1 being the most common and least severe. Some people with type 1 have no symptoms and do not require treatment.
Chiari malformation type 1 Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.
Chiari malformation type 2
Chiari malformation type 3
Chiari malformation type 4