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Chiari Malformation

What is a Chiari malformation?

A Chiari malformation (pronounced key-ari mal-for-MAY-shun) means the cerebellum and/or the brainstem are not shaped properly and there is not enough space for these structures.

The cerebellum is a part of the brain that affects balance and coordination. The brainstem connects the spinal cord with the brain.

In a Chiari malformation, this back portion of the brain is pushed through a hole in the bottom of the skull and into the cervical spinal canal (the neck area). This limits the flow of cerebrospinal fluid to this area.

There are four different types of Chiari malformations. Because types III and IV are very rare, we discuss only types I and II here.

Chiari I malformation

This condition involves a too-small or poorly shaped back area of the skull called the posterior fossa. The brainstem and cerebellum are the posterior fossa. The bottom portion of the cerebellum comes down into the cervical spinal canal.

This crowding often limits the amount of CSF that flows from the brain to the spinal cord.

Quite often, a child with a Chiari I malformation has no symptoms. They may not appear until the child is a teenager or young adult. Symptoms may worsen with physical effort or straining, such as coughing. They can include:

  • Headaches in the back of the head
  • Neck pain
  • Dizziness
  • Numbness
  • Pain or tingling in the arms
  • Difficulty with small (fine) motor tasks such as writing or cutting with scissors
  • Decreased gag reflex

Chiari II malformation

A Chiari II malformation involves more of the brain than Chiari I. A significant portion of the cerebellum, the lower part of the brain stem and the brain’s fourth ventricle, are pushed down into the cervical spinal canal.

Chiari II symptoms are usually worse than those of Chiari I and other symptoms may be present, such as:

  • Trouble swallowing
  • An abnormal, high-pitched sound when breathing in called strider
  • Accidentally breathing tiny bits of food, fluids or saliva into the lungs (aspiration)
  • Arm weakness, numbness and tingling

Who gets a Chiari malformation?

Chiari malformations are most often present at birth (congenital). Some children can develop Chiari I malformations for complex reasons. Chiari I malformations may be diagnosed in children and adults.

Chiari II malformations occur in children with a myelomeningocele, and hydrocephalus. These three conditions occur together and are a complex birth defect.

Patients with a Chiari I or II malformation may have a collection of fluid in the spinal cord called a syringomyelia or syrinx.

What is your experience with Chiari malformations?

Surgeons at Children’s have a particular interest in Chiari malformations. Children from all over the United States come to us for treatment. We do about 40 Chiari operations a year.

We also follow many children with myelomeningocele and Chiari II malformations in a multidisciplinary clinic called the Neurodevelopmental Clinic.

What surgery do you use to treat Chiari malformation?

We base a child’s need for surgery on three things:

  1. MRI findings
  2. Symptoms
  3. Whether there is a syringomyelia, also called a syrinx

We can treat this complex problem in several ways. Together, your doctor and family will make the best choice for treatment.

Posterior fossa decompression

This special kind of craniotomy is the most common treatment for Chiari malformation. When operating on a Chiari malformation, the neurosurgeon removes a small portion of bone from the base of your child’s skull. Sometimes it is also necessary to remove part of the bones from the first one or two cervical bones (vertebrae) of the spine. The surgeon may open the brain’s tough cover (the dura mater) in the affected area and places a patch on the dura. The patch is usually from tissue outside the skull. Doing this creates more space for the effected brain structures.

The goal of surgery is to create more room for the cerebellum and the brain stem. This relieves some pressure on the cerebellum, allowing a more normal flow of CSF in the area. If your child also has a syrinx, this surgery usually allows it to drain.