Chiari Malformation

What is Chiari malformation?

Chiari malformation is an abnormality in the back of the head where the brain and spinal cord meet. It causes some of the brain tissue at the base of the skull to be pushed into the spinal canal. This can cause pressure on the brain and block the normal flow of spinal fluid in and around the brain. Sometimes this leads to a buildup of spinal fluid within the spinal cord, called a syrinx.

What are the types of Chiari malformation?

There are four types of Chiari malformation. They are categorized by which parts of the brain are pushed into the spine and the severity of the condition:

  • Chiari malformation type I is the most common. It’s the only type that can also develop after birth. People with type I often have no symptoms and need no treatment.
  • Chiari malformation type II almost always affects children who have spina bifida and develops before birth. Most children with type II Chiari malformation need surgery.
  • Chiari malformation type III is very serious, but rare. In this type, some parts of the brain may protrude from the skull. It usually causes severe disabilities.
  • Chiari malformation type IV is also very serious and very rare. In this type of Chiari malformation, part of the brain is not developed or is missing.

Because type III and type IV Chiari malformations are so rare, we will focus only on type I and type II on this website.

What are the symptoms of type I Chiari malformation?

Children with type I Chiari malformations often have no signs or symptoms. In many cases, they are diagnosed after having a magnetic resonance imaging (MRI) scan for another problem.

When symptoms do occur, they most often start in the teen years or early adulthood. These may include:

  • headaches, especially when coughing, sneezing, or straining
  • neck pain
  • balance problems
  • dizziness
  • trouble swallowing
  • numbness or tingling in the arms or legs
  • vision problems
  • breathing problems, especially during sleep
  • loss of bowel or bladder control
  • a curve of the spine, called scoliosis

What are the symptoms of type II Chiari malformation?

Children with type II Chiari malformations are more likely to have symptoms. These may include:

  • a build-up of fluid in the brain (hydrocephalus)
  • a weak cry
  • trouble swallowing
  • breathing problems
  • problems with nerve function in the throat and tongue

What are the causes of Chiari malformation?

  • Type I: This type occurs if the skull is too small or if the brain grows more quickly than the skull, causing the bottom of the brain to push into the spinal canal.
  • Type II: Almost all children with a type II malformation have a form of spina bifida called myelomeningocele, when the backbone and spinal canal don’t close before birth.

How we care for Chiari malformation

At Boston Children’s Hospital, our team of experts in the Department of Neurosurgery has years of experience helping infants, children, and teens who have been diagnosed with a Chiari malformation.