A Chiari malformation is a defect in which a part of the brain at the back 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 four 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. In type II, two parts of the brain (the cerebellum and brain stem) bulge through the foramen magnum.

This problem can happen in newborns who have spina bifida or spinal myelomeningoceles. A myelomeningocele occurs 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.

Chiari II malformations are present at birth (congenital). Experts don't know what causes this malformation. They think that something happens to the fetus that causes the brain to form abnormally. Research is being done to find out if the cause may be genetic. Most often, no cause is known.

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.

The diagnosis is often done at birth. This malformation usually occurs with other birth defects. The doctor may be able to find the defect during pregnancy with a fetal ultrasound.

Imaging tests are done to find Chiari malformations. Your child may need the following tests:

• MRI. This test uses large magnets, radio waves, and a computer to create detailed pictures of organs and other 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 doctor 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.

Your child may need to see several kinds of doctors 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.

Your child may also need:

• Treatment for bowel and bladder problems.
• Special feedings.
• Breathing support.

Complications of Chiari malformations include:

• Syrinx develops in the spinal cord or gets worse.
• Permanent damage to muscles or nerves.
• Paralysis.
• Loss of control of bowel and bladder.
• Too little oxygen gets to your child's lungs (respiratory failure).

A Chiari malformation can be fatal.

Doctors 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 doctor 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

Contact your child's doctor 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 doctor if your child has a severe headache or neck pain.