What Is a Chiari Malformation?
A Chiari malformation (pronounced key-AR-ee mal-for-MAY-shun) is a problem in the way parts of the brain are shaped. In children who have a Chiari malformation, the cerebellum, the brainstem or both structures are pushed down because the back of the skull is smaller than normal.
The cerebellum affects balance and coordination. The brainstem connects the spinal cord with the brain. In a Chiari malformation, this back portion of the brain pushes through a hole in the bottom of the skull into the neck area (cervical spinal canal). This limits the flow of cerebrospinal fluid (CSF) to the area.
There are four different types of Chiari malformations. Because types 3 and 4 are very rare, we discuss only types 1 and 2 here:
- Chiari 1 involves a too-small or poorly shaped back area of the skull (posterior fossa). The bottom portion of the cerebellum comes down into the neck area. This crowding often limits the amount of cerebrospinal fluid that flows from the brain to the spinal cord.
- Chiari 2 malformation involves more of the brain than Chiari 1. A portion of the cerebellum, the lower part of the brain stem and the brain’s fourth ventricle are pushed down into the neck area.
Chiari Malformation in Children
Often, Chiari malformations are present when a child is born (congenital). Some children can develop Chiari 1 malformations after birth. Sometimes, doctors may not find Chiari 1 malformations until children have grown to adulthood.
Chiari 2 malformations often happen in children who also have two other conditions: myelomeningocele and hydrocephalus. Together, these three conditions form a complex birth defect.
Children with a Chiari 1 or 2 malformation also may have a collection of fluid in the spinal cord called syringomyelia (pronounced se-ringo-my-EEL-e-ah).
Chiari Malformation at Seattle Children’s
Children from across the United States come to Seattle Children's for treatment of Chiari malformations. Our neurosurgeons perform about 40 operations on children with these conditions each year. In our Neurodevelopmental Clinic, we work closely with experts in many medical areas to care for children with Chiari malformations.