Chiari malformations are defects in the back of the skull where the brain meets the spinal column. It allows a part of the cerebellum, the lowest portion of the brain, to protrude downward into the spinal column.
This causes pressure and sometimes limits the flow of cerebrospinal fluid (CSF) between the brain and spinal column. This sometimes leads to hydrocephalus. Depending on how restricted the flow of CSF is, it can cause such symptoms as headaches, dizziness and balance issues, chest pain, numbness and weakness.
Chiari malformations can accompany other birth defects such as spina bifida. There are four different types of Chiari malformations, with I being the mildest and IV the most severe. Mild cases do not require intervention and can simply be watched. More severe malformations may require a surgical solution.