What is a Chiari malformation?

Chiari malformations, also known as Arnold-Chiari malformations, are structural defects in the cerebellum, which controls balance, according to WebMD. Although some people with a Chiari malformation have no symptoms, other people experience dizziness, numbness, muscle weakness, headaches and problems with balance and coordination.

More common in women than in men, the condition affects at least 1 in every 1,000 births, reports WebMD. Chiari malformations usually occur before birth but can develop after birth due to infection, injury or exposure to a toxic substance. There are four types of Chiari malformations. The second type is most commonly seen in children with spina bifida.