What is a Chiari II malformation?

A Chiari malformation is a structural defect in which a part of the brain at the rear of the skull bulges through a normal opening (foramen magnum) in the skull where it joins the spinal canal. This puts pressure on parts of the brain and spinal cord. It can cause mild to severe symptoms. In most cases, the problem is present at birth (congenital).

There are 4 main types of Chiari malformations: types I, II, III, and IV. In some cases, you may see type IV referred to as cerebellar hypoplasia and not included as one of the Chiari malformation types. Type I is the most common. This article is about type II. In this type, two parts of the brain (the cerebellum and brainstem) bulge through the foramen magnum.

This problem can happen in newborns who have spina bifida or spinal myelomeningoceles. A myelomeningocele is when part of the spinal cord and meninges grow outside the body instead of inside.

A common problem with type II malformations is too much spinal fluid in the brain (hydrocephalus). The extra fluid puts more pressure on the brain. The bones of the skull expand to a larger-than-normal size.

What causes a Chiari II malformation?

Chiari II malformations are present at birth (congenital). Medical experts don’t know what causes this malformation. They think that something happens to the fetus while it is growing that causes the brain to form abnormally. Experts are doing research to determine if the causes may be genetic. Most often, no cause is known.

What are the symptoms of a Chiari II malformation?

Symptoms of Chiari II malformations depend on the age of your child. Newborns may have:

• Spinal myelomeningocele or spina bifida

• Noisy breathing

• Trouble swallowing

• Problems with breathing food or fluid into the lungs (aspiration)

• Short periods of not breathing (apnea)

• Weakness in the arms

Older babies and children may have:

• Hydrocephalus that gets worse over time

• Abnormal shape of the spine (scoliosis)

• Eyesight problems

• Hearing loss

• Trouble using their hands to pick up and use small objects

Children may also have extra fluid in the brain stem or spinal cord (syrinx). This may cause pain in the arms or legs or make it hard for your child to walk.

How is a Chiari II malformation diagnosed?

The diagnosis is often done at birth. This is because a Chiari II malformation usually occurs with other birth defects. The healthcare provider may also be able to find the defect during pregnancy with a fetal ultrasound.

The healthcare provider uses imaging tests to find Chiari malformations. Your child may need the following tests:

• MRI. This test uses a combination of large magnets, radio waves, and a computer to create detailed pictures of organs and structures within the body. It does not use X-rays. MRI is the best test for diagnosing Chiari malformations. If an MRI can’t be done, the provider may order a high-resolution CT scan.

• CT scan. This test uses X-rays and a computer to make detailed pictures of the body. A CT scan shows bones, muscles, fat, and organs.

• Ultrasound. This test uses sound waves and is more accurate in newborns and babies before the skull has closed.

How are Chiari II malformations treated?

Your child may need to see several kinds of healthcare providers for treatment. These include experts in brain and spinal cord problems (neurologists and neurosurgeons).

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.

Treatment for a Chiari II malformation may include surgery to:

• Ease pressure on the brain and let spinal fluid flow (decompression).

• Close a myelomeningocele. This may be right after birth.

• Put a flexible tube (shunt) in the brain. This is to drain extra fluid (hydrocephalus).

• Put a shunt in the spinal cord to drain fluid from a syrinx.

Your child may also need:

• Treatment for bowel and bladder problems

• Special feedings

• Breathing support

What are possible complications of a Chiari II malformation?

Complications of Chiari malformations include:

• Syrinx develops or gets worse

• Permanent damage to muscles or nerves

• Paralysis

• Too little oxygen gets to your child’s lungs (respiratory failure)

A Chiari malformation can also be fatal.

How are Chiari II malformations managed?

Healthcare providers can’t often tell what will happen in a child with a Chiari malformation. Your child may stay about the same. Or your child may have nerve or brain problems that get worse. Your child’s healthcare provider will watch your child closely. Some children with Chiari II can function well. Your child will need physical exams and imaging tests done often. 

Your child may need ongoing care:

• Speech therapy for swallowing problems

• Nutrition therapy

• Physical, occupational, and rehabilitation therapy

When should I call my child's healthcare provider?

Call your child’s healthcare provider right away if you see any changes in your child. Call if you notice problems with:

• Breathing

• Swallowing

• Feeding

• Speaking

• Walking or moving

Also call your child’s provider if your child has a severe headache or neck pain.