Chiari Malformation

A Chiari malformation (kee-AHR-ee  mal-for-MAY-shun) is where the back of the brain (called the cerebellum) goes down below the base of the skull and into the upper spinal canal. Children may be born with this malformation or can develop it later in childhood. In many instances, a fluid collection is found in the spinal cord because of the Chiari malformation. This fluid collection is called a syrinx.

There are four types of Chiari malformation:

  • Chiari I is the most common type
  • Chiari II, often called the Arnold-Chiari malformation, is mostly found in children with spina bifida
  • Chiari III and IV are very rare and may be life-threatening

It is not clear why Chiari malformations develop.  Doctors think one of the causes may be that the part of the skull that holds the back part of the brain is smaller. The small skull means there is not enough room for the brain and possibly the spinal cord.

A Chiari malformation may cause a variety of symptoms.  chiari-malformation1

Symptoms in infants and young children often include:

  • Trouble feeding and swallowing, which may lead to gagging, drooling and vomiting
  • Abnormal breathing (may have slow or noisy breathing that sounds like snoring)
  • Irritability, head banging and night-time awakening (may all be signs of headache in young infants)

Symptoms in older children commonly include:

  • Headache
  • Spinal curvature
  • Clumsiness
  • Difficulty controlling bladder function, in rare cases

An MRI scan is the best way to diagnose a Chiari malformation. You can see the brain and upper spinal cord from many angles, which helps to make an accurate diagnosis. chiari2

Other tests may also help in evaluating patients with Chiari malformations:

  • An MRI scan of the entire spine can see if the spinal cord is too low in the spinal canal. This problem is known as a tethered cord. It is found in a small number of patients with a Chiari malformation. There may also be a fluid-filled cavity (called a syrinx) within the spinal cord.
  • A swallowing test can tell how well the child is able to drink liquids or swallow thickened food. This test is helpful for children who have gagging or excessive drooling.
  • A sleep study can look at a child’s breathing pattern and tell if there is enough oxygen getting to the brain during sleep. This test is helpful for children who have a history of noisy sleeping or snoring.

Sometimes children have a Chiari malformation diagnosed by an MRI scan but have no symptoms. These children usually do not need surgery. A follow-up MRI scan may be recommended to see if the Chiari malformation changes.

What is the best treatment for Chiari malformations?

Surgery is the best treatment for children with Chiari malformations. The surgery makes more space for the brain and the spinal cord. Without surgery, a child would continue to have symptoms that may get worse over time.

What happens during surgery?

Surgery will increase the space at the bottom of the brain, where it connects to the spine. 

  • First, a small cut is made at the back of the head. 
  • The muscle is gently moved out of the way.
  • A small piece of bone is removed from the bottom of the skull to create the extra space. 
  • The doctor may use a machine that is like an X-ray to see if the space is big enough. If the space is OK, the surgery is over and the cut is sewn up. 
  • The muscle and tissue in this area will protect the brain

If more space is needed:

  • The doctor makes a cut in the covering of the brain, called the dura mater. 
  • The doctor may need to sew a patch over the opening to keep spinal fluid from leaking.  
  • There is also some brain tissue, called brain tonsils, found at the back of the head near the spinal opening. Brain tonsils do not have any purpose. 
  • Sometimes, the doctor may shrink the brain tonsils to make more room.

Children having this surgery need regular follow-up visits to make certain the symptoms do not return.


Last Updated 07/2013