What is Chiari malformation?

Chiari malformation is where the bottom of your brain pushes into your spinal canal. Your spinal canal is the space where your spinal cord sits.

This may cause a build-up of pressure on your brain stem and spinal cord. It can also block the flow of cerebrospinal fluid. Cerebrospinal fluid is a clear liquid that protects your brain and spinal cord.

People with a Chiari malformation usually have it from birth.

What are the types of Chiari malformation?

There are 4 main types of Chiari malformation. These affect different parts of your brain.

1. Type 1 — the lower part of the brain (cerebellum) extends into the spinal canal. This is the most common type.
2. Type 2 (or Arnold-Chiari malformation) — both the cerebellum and brain stem tissue extend into the spinal canal.
3. Type 3 — some of the cerebellum and brain stem stick out through the back of the skull. Type 3 is very rare and can cause life-threatening complications in infancy.
4. Type 4 — the cerebellum is not complete or underdeveloped. Type 4 is also very rare and is usually fatal (causes death) in infancy.

What are the symptoms of Chiari malformation?

Some people don’t have any symptoms. Others may have symptoms and may need surgery.

Symptoms of Type 1 Chiari malformations often start during infancy. Although in some people the symptoms may not start until adolescence or adulthood.

Severe headaches is one of the main symptoms of Chiari malformation.

The headache normally happens after coughing or straining. The pain is at the back of the head towards your neck. The pain generally goes away after about 5 minutes.

Other symptoms can include:

• neck pain
• dizziness and balance problems
• muscle weakness
• numbness or tingling in your arms or legs
• swallowing problems
• nausea and vomiting
• hearing loss or ringing in the ear (tinnitus)

Some babies may also have hydrocephalus (too much cerebrospinal fluid in their skull).

What causes Chiari malformation?

The exact cause of Chiari malformation Type 1 is unknown.

Type 1 malformation may be caused by:

• your skull not being big enough for your brain
• a tethered spinal cord
• hydrocephalus (too much fluid on your brain)
• some types of brain tumour

Chiari malformations can sometimes run in families.

When should I see my doctor?

If you are concerned that you may have symptoms, you should see your doctor.

You should also see your doctor if you have a diagnosis of Chiari malformation and your symptoms worsen.

How is Chiari malformation diagnosed?

Your doctor will examine you and ask about your symptoms. They may check your:

• balance
• reflexes
• motor skills
• memory

Your doctor may also organise imaging, such as an:

• MRI scan
• CT scan

Chiari malformations are usually present from birth. However, they tend to be diagnosed only when symptoms appear.

Sometimes, if you have no symptoms, Chiari malformation is only diagnosed when you have a scan for another reason.

There is currently no reliable screening test to tell if a baby will be born with a Chiari malformation. Some malformations can be seen on ultrasound images before birth.

How is Chiari malformation treated?

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

You may need pain-relief medicines to relieve any headaches and neck pain.

Depending on the severity of your symptoms, your doctor may recommend that you have surgery.

Decompression surgery

The aim of surgery is to create more space for your cerebellum. It’s called decompression surgery. This relieves the pressure on your spinal cord.

A cut is made at the back of your head. Your doctor will remove a small piece of bone from the base of your skull.

Sometimes they will also take a small piece of bone from the top of your spine.

This is done under general anaesthetic, so you won’t feel anything.

You should discuss with your doctor the risks and benefits of surgery. It’s important to understand what improvements you may expect after surgery.

The aim of surgery is to stop your symptoms getting any worse.

Living with Chiari malformation

Many people who have surgery for Chiari malformation experience an improvement in their symptoms.

Can Chiari malformation be prevented?

Researchers are looking at the best ways to diagnose, treat and prevent Chiari malformations.

Complications of Chiari malformation

You may develop syringomyelia (where a fluid-filled cavity develops in your spinal cord).

Babies with very serious malformation types may have life-threatening complications.

Resources and support

For more information and support, visit the Brain Foundation.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.