What is Chiari malformation?

Chiari malformation (or Arnold-Chiari malformation) is a condition where part of the brain pushes down into the spinal canal, through which the spinal cord runs. People with a Chiari malformation usually have it from birth. Some people don’t have any symptoms. Others may have symptoms and may need surgery.

Normally, the lower part of the brain, known as the cerebellum, and part of the brain stem sit above an opening in the skull that allows the spinal cord to pass through it. If part of the skull is smaller than normal or misshapen, it may push the cerebellum into the spinal canal. This may cause a build-up of pressure on the brain stem and spinal cord. It can also block the flow of cerebrospinal fluid, which is a clear liquid that protects the brain and spinal cord.

What are the types of Chiari malformation?

There are 4 types of Chiari malformation depending on the part of the brain that is pushed down into the spinal canal.

Type 1

Type 1 occurs when the lower part of the cerebellum extends into the spinal canal. It is the most common type. People with type 1 may not have any symptoms or may develop symptoms when they are teenagers or adults.

Symptoms can include:

• headaches
• neck pain
• swallowing problems
• muscle weakness
• vomiting
• dizziness and balance problems
• ringing in the ear (tinnitus)

Type 2

Type 2 occurs when both the cerebellum and brain stem tissue extend into the spinal canal. People with type 2 usually also have a condition called myelomeningocele where the spinal canal and backbone do not close before birth.

Symptoms of type 2 are generally more serious than those of type 1 and are usually noticed in childhood. These may include:

• changes in the breathing pattern
• gagging
• involuntary, quick, downward eye movements

Type 3 and type 4

Type 3 and type 4 are rare but may be life-threatening. In type 3, some of the cerebellum and brain stem stick out through an abnormal opening in the back of the skull. In type 4, the cerebellum is not complete or underdeveloped.

What causes Chiari malformation?

Chiari malformation is usually present from birth. It is commonly caused by abnormal brain or spinal cord development of a baby in the womb. But it can also develop later in life due to injury, disease or infection.

How is Chiari malformation diagnosed?

There is currently no reliable screening test to tell if a baby will be born with a Chiari malformation. But sometimes ultrasound images of the baby in the womb can show they have the condition.

Chiari malformation is usually diagnosed through a magnetic resonance imaging (MRI) or CT scan.

Sometimes, if the condition does not cause any symptoms, it may be diagnosed only during an MRI or CT scan carried out for another reason.

How is Chiari malformation treated?

Treatment will depend on the symptoms. If you have Chiari malformation without any symptoms, your doctor may just monitor your condition.

If you develop symptoms or your symptoms worsen, you need to tell your doctor. You may need painkillers to relieve any headaches and neck pain. Depending on the severity of your symptoms, your doctor may recommend that you have surgery. The aim of surgery is to create more space for the cerebellum and relieve pressure on your spinal cord. You need to discuss with your doctor the risks and benefits of surgery.

Living with Chiari malformation

Many people who have surgery for a Chiari malformation experience an improvement in their symptoms. It is important to speak with your doctor about what you may expect after surgery.

Resouces and support

For more information and support, visit Brain Foundation.

There is a closed Australian Facebook group for people with Chiari malformation.