What is Chiari Malformation?

Chiari malformation is an abnormality in the back part of the head where the brain and spinal cord meet. It causes some of the brain tissue in the lower part of the brain to be pushed through the opening at the bottom of the skull and into the spinal canal. This can put pressure on parts of the brain and spinal cord, block the normal flow of spinal fluid in and around the brain, and lead to a buildup of spinal fluid within the spinal cord.

In most cases, Chiari malformation is present at birth (congenital).

What are the types of Chiari Malformation?

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

• Chiari malformation type I – This is the most common type of Chiari malformation. Part of the cerebellum dips down through the bottom of the skull. This type is most often congenital. In rare cases, it can develop after birth from a loss of spinal fluid due to an injury, contact with harmful substances, or an infection. Type I Chiari malformation is often not found until a child is a teen or young adult. People with type I Chiari malformation often have no symptoms and need no treatment.
• Chiari malformation type II – This type, also known as Arnold-Chiari malformation, develops before birth and is seen in babies born with spina bifida. Part of the cerebellum and the brain stem are pushed down through the opening at the bottom of the skull and into the spinal canal. Type II Chiari malformation can cause too much fluid in the brain (hydrocephalus). The extra fluid causes the pressure in the brain to increase and the skull bones to expand beyond normal size. Most children with type II Chiari malformation need surgery
• Chiari malformation type III – This is the most severe and rare type of Chiari malformation. The cerebellum, brain stem and possibly other parts of the brain are pushed down through the opening at the bottom of the skull. In rare cases, some parts of the brain may poke out through the back of the head or neck. A baby with type III Chiari malformation may not live long. Children who do survive will have severe disabilities.
• Chiari malformation type IV – This is a very rare type of Chiari malformation in which the brain doesn’t fully develop, or part of the brain is missing. Most babies with type IV Chiari malformation don't survive.

Because type III and type IV Chiari malformations are extremely rare, the information that follows focuses on diagnosis and treatment of type I and type II Chiari malformations at Children's Hospital of Philadelphia's Neuroscience Center.

Signs and symptoms of Chiari malformation

Most children with type I Chiari malformation often have no symptoms, or their symptoms develop slowly over time and aren’t recognized until their teen or early adult years. In many cases, they are diagnosed after having a magnetic resonance imaging (MRI) scan for another problem.

Symptoms of type I Chiari malformation may include:

• Headaches
• Pain in the back of the head or neck, especially when coughing, laughing or sneezing
• Trouble swallowing
• Balance issues
• Weakness or abnormal movements
• Rapid eye movements
• Hoarseness or trouble speaking
• Abnormal shape of the spine (scoliosis)
• Breathing problems, especially during sleep (sleep apnea)
• Trouble walking or pain in the arms or legs

Children with type II Chiari malformation are more likely to have the following symptoms:

• Build-up of fluid in the brain (hydrocephalus)
• Weak cry
• Trouble swallowing
• Breathing problems
• Problems with nerve function in the throat and tongue

Causes of Chiari malformation

Type I Chiari malformation 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 Chiari malformation most often occurs in children with the most serious form of spina bifida, called myelomeningocele. In this condition, the backbone and spinal canal don’t close before birth.

Testing and diagnosis for Chiari malformation

At Children's Hospital of Philadelphia's Neuroscience Center, your child’s care begins with a comprehensive, personalized assessment of their medical history and symptoms.

The diagnosis of Chiari malformation is made after a physical examination and one or more of the following imaging tests:

• Magnetic resonance imaging (MRI) exam – An MRI uses powerful radio waves and magnets to create a detailed picture of the brain, spinal cord or other organs. These pictures can identify many different types of abnormalities in the brain and help in the diagnosis of your child’s particular form of Chiari malformation. MRI is a safe, painless test that produces detailed 3D images of structural differences in the brain that may be contributing to your child’s symptoms. It can also provide images of the cerebellum and determine whether it extends into the spinal canal. MRI may require sedation in young children to help them stay still and comfortable. Your care team can discuss this further with you.
• Computed tomography (CT) scan ­– A CT scan uses a series of X-rays to create a cross-sectional image of the body. The CT machine makes images that are more detailed than a regular X-ray.

In a child with no symptoms, Chiari malformation may be diagnosed when imaging tests are done for other reasons.

Chiari malformation Treatment

At the Neuroscience Center, the goal of treatment is to stop symptoms from interfering with a child’s normal growth and development, with as few treatment-related side effects as possible. Treatment for Chiari malformation depends on the severity and characteristics of your child’s condition. Very severe Chiari malformations may be life-threatening.

• Medical Management – If your child has no symptoms, your doctor will likely recommend no treatment other than regular physical examinations and MRIs to monitor the growth and development of your child’s brain, spinal cord, skull and backbones. If headaches or other types of pain are the primary symptom, your doctor may recommend pain medication.
• Surgery – If your child has symptoms, they will likely need surgery to relieve pressure on the brain or to restore the normal flow of spinal fluid. The specific type of surgery your child’s doctor recommends will depend on:
  • Your child’s age, overall health and medical history
  • The severity of your child’s symptoms
  • The type of Chiari malformation

The most common surgery for Chiari malformation is posterior fossa decompression. During this procedure, the surgeon removes a small section of bone in the back of your child's skull. In some cases, the covering over the brain and spine is also opened.  This helps relieve pressure by giving the brain more room and reduces symptoms. The surgeon may also use an electrical current to shrink some of the tissue.

Learn more about our comprehensive treatment options in our Chiari Malformation FAQ Guide for Caregivers.