A Chiari malformation is a brain abnormality that affects the lower part of the brain, called the cerebellum. Many kids with this abnormality don't know they have the condition because they never have symptoms, and therefore aren't bothered by it.

But if you're reading this, chances are your child probably has some symptoms associated with a Chiari malformation. If that's the case, talk to a specialist — a pediatric neurologist or pediatric neurosurgeon — to determine what kind of treatment can help. Depending on your child's condition, medicines and procedures are available to help alleviate the symptoms of Chiari malformation.

About Chiari Malformation

Chiari (pronounced key-are-ee) malformation is a brain abnormality that causes the cerebellum, the part of the brain that controls coordination and muscle movement, to protrude into the space normally occupied by the spinal cord. Some children are born with the condition, and others develop it as they grow.

Chiari malformation sometimes happens because the space at the back of the skull, where the cerebellum sits above the spine, is too small or is unusually shaped. These "cramped quarters" squeeze the cerebellum and even part of the brain stem, which controls the nerves in the face and neck, down through the foramen magnum (a funnel-like hole below the skull through which only the spinal cord usually passes).

Chiari malformation is also sometimes called tonsillar herniation or tonsillar ectopia because the part of the cerebellum that descends into the foramen magnum is called the cerebellar tonsils.

The pressure caused by Chiari malformation on the cerebellum, brain stem, and spinal cord can keep them from working correctly. It can also block the movement of cerebrospinal fluid (CSF), the liquid that surrounds the brain and spinal cord and protects them from injury. When CSF doesn't flow properly, it can build up in the brain and spinal cord and block communication of the brain's messages to the body.

There are four different types of Chiari malformation (I, II, III, and IV). Type I is by far the most common in children.

Causes

Doctors may refer to a Chiari malformation as "congenital," which means that a child developed it in the womb and had it at birth. Most cases of Chiari malformation are congenital, and often the cause is unknown.

Chiari malformations also can be related to other disorders that affect the development of the brain, spine, and bones. A Chiari malformation that is acquired develops later in life. When this happens, it's usually the after-effect of brain or spinal surgery performed for an unrelated condition. Acquired cases of Chiari malformation are sometimes reversible.

Although doctors haven't been able to identify a gene that causes Chiari malformation, it does sometimes run in families, which indicates that it could be hereditary.

Signs and Symptoms

Many kids with type I Chiari malformation have no signs and symptoms and don't even know that they have a malformation. They find out about it only when they're tested for another problem.

But if a Chiari malformation is severe enough to block the flow of CSF or put significant pressure on the brain or spinal cord, a child's nervous system can be affected. Symptoms can include dizziness and problems with balance and coordination. This means a child might fall down a lot, walk unusually, have trouble grasping items, or have poor hand-eye coordination.

Other symptoms can include:

• neck or chest pain
• headaches that are brought on by coughing, sneezing, or laughing
• difficulty swallowing, which may cause gagging, choking, or vomiting
• difficulty speaking
• rapid eye movements or vision problems like light sensitivity or blurred vision
• hearing problems like a tinnitus (ear ringing) or hearing loss
• weakness, numbness, tingling, or other abnormal feelings in the arms and legs
• insomnia
• depression

Signs of Chiari malformation in babies include:

• irritability when being fed
• excessive drooling
• weak cry
• trouble gaining weight
• arm weakness
• developmental delays

Some children with Chiari malformations also have cognitive and behavioral problems. Doctors aren't sure whether a Chiari malformation directly causes these problems or whether they're simply the child's way of reacting to the condition and its symptoms.

Since the symptoms of Chiari malformations vary greatly and may mimic many other conditions, it's important to get an accurate diagnosis. If you feel unsure about your child's diagnosis, seek a second opinion.

Related Conditions

Children with Chiari malformations might have other conditions that are associated with the abnormality, such as:

• Hydrocephalus: An excessive buildup of CSF in the brain that causes an enlarged skull and, if left untreated, can lead to brain damage, a loss in mental and physical abilities, and even death.
• Syringomyelia: A disorder in which a cavity called a syrinx develops in the spinal cord. This cavity usually fills with fluid and stretches the spinal cord, which can cause permanent nerve damage and paralysis.
• Scoliosis: A condition that causes a curvature of the spine. Scoliosis can be a complication of syringomyelia, which causes an imbalance in the strength of the muscles that hold the spine straight and upright.

Diagnosis

Chiari malformation can be linked to certain birth defects, so children born with these defects are usually tested to see whether they might also have a Chiari malformation.

Most people with Chiari malformation (usually type I) appear healthy. So the diagnosis can come as a surprise and often follows testing, examination, or treatment for another condition. Chiari malformation also might be hard to diagnose in these cases because the symptoms are vague and can be caused by many other conditions. Often, people with type I Chiari malformation aren't diagnosed until they're teens or adults.

If your doctor suspects a Chiari malformation, your child will be examined and tested for things like speech, balance, reflexes, and motor skills. The doctor will probably want your child to undergo one or more of these tests:

• Magnetic resonance imaging (MRI), a safe and painless test that uses magnets, radio waves, and computer technology to produce very good pictures of internal body parts, such as the brain and spinal cord. It can help to determine the severity of a malformation and to monitor it later on. Your child may be given an injection of a dye called a contrast medium to improve the images. The test can take up to an hour to complete.
• Cine MRI is a specific type of MRI that doctors use to see whether the flow of CSF from the brain to the spinal cord is blocked.
• X-rays produce images of bones on film and can detect bone abnormalities caused by Chiari malformations. They are painless, quick, and safe.
• Computed tomography (CT or CAT) scans produce pictures of bones and other body parts using X-rays and a computer. Scanning is quick and painless and can detect obvious blockages or measure how much of the brain is out of place.
• Brainstem auditory evoked response (BAER), a test that measures brain activity in response to sound, helps to determine whether the brain stem is working correctly.
• Somatosensory evoked potential (SSEP) testing helps determine whether messages from the brain can properly travel through the spinal cord.

Currently, no test can determine in advance whether a baby will be born with a Chiari malformation; however, some malformations can be seen on ultrasound images before birth.

Treatment

There is no cure for Chiari malformation. However, most children who don't have symptoms won't require treatment. They should, however, continue to see their doctors for regular checkups to make sure that their condition doesn't change.

When symptoms do occur, treatment will focus on relieving them and stopping further damage to the brain and spinal cord (for example, medications may be used to ease symptoms like headaches and neck pain). And sometimes the doctor will recommend limiting activities that worsen symptoms.

If symptoms become severe, you may be referred to a neurosurgeon to discuss whether surgery is a good idea for your child.

A common procedure for kids with Chiari malformation is decompression. It helps to relieve pressure on the brain and spinal cord, restore the flow of CSF, and prevent additional damage. This surgery usually takes several hours and involves removing part of the skull and a portion of the spine's top vertebra.

Another surgical option involves implanting a shunt or tube to help drain CSF and relieve pressure on the brain. Shunts are commonly used to help children who have hydrocephalus or syringomyelia.

Surgery isn't a cure but it can help to greatly improve the problems caused by a Chiari malformation. It does have drawbacks, though. Surgery can be painful and can put a child at risk for infection and other complications. That's why it's important to talk to your doctor and weigh the pros and cons when deciding what is best.

Since doctors sometimes disagree on the best way to treat Chiari malformations, it's also wise to get a second opinion before making a decision.

Outlook

The less severe the condition, the better the prognosis is for kids with Chiari malformations.

Many kids do not experience health problems and those with mild symptoms usually find that medications provide enough relief for them to lead normal lives. Symptoms typically don't get worse and surgery usually isn't necessary for kids with these milder forms.

For those who do undergo surgery, a successful long-term outcome depends on the severity of symptoms and how long they existed prior to surgery — kids whose symptoms were present for a brief period before surgery are more likely to have symptoms resolve compared with those who had symptoms for many years.

Reviewed by: Joseph H. Piatt, MD
Date reviewed: July 2011