Chiari malformation (pronounced key-AR-ee mal-fore-MAY-shun) is brain deformity that affects the lower part of the brain, called the cerebellum.
Many kids with this condition aren't bothered by it, and don't have any symptoms. But for some, Chiari malformations can cause headaches, balance problems, and other symptoms.
What Is a Chiari Malformation?
Chiari malformation is a condition that causes the cerebellum — the part of the brain that controls coordination and muscle movement — to push into the space normally occupied by the spinal cord. Most kids who have it are born with the condition, but some develop it as they grow.
Normally, the cerebellum sits at the back of the skull, just above the spine. When a child has a Chiari malformation, the space for the cerebellum is sometimes too small or unusually shaped. This can squeeze part of the cerebellum and even part of the brain stem (the part of the brain that controls nerves in the face, mouth, throat, neck, and spine) down through a funnel-like hole below the skull. This hole is called the foramen magnum, an area through which only the spinal cord usually passes.
When this happens, it can put pressure on the cerebellum, brain stem, and spinal cord and can keep those body parts from working properly. It also can 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 cause hydrocephalus (a buildup of CSF in the brain and spinal cord). This buildup can block communication of the brain's messages to the body and cause headaches, pain, numbness, and weakness.
There are four different types of Chiari malformation (I, II, III, and IV). Type I is the most common.
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.
When a child is not born with it, it can be caused by (or related to) other disorders that affect the development of the brain, spine, and bones, such as hydrocephalus, scoliosis,spina bifida, or syringomyelia, a problem with the spine that can lead to nerve damage or paralysis. Chiari malformations also can happen after brain or spinal surgery.
Doctors haven't identified a gene that causes Chiari malformation, but it does sometimes run in families. This means that it could be a hereditary condition.
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.
If a Chiari malformation is severe enough to block the flow of CSF or put pressure on the brain or spinal cord, the nervous system can be affected. If so, 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.
Some children with Chiari malformations also have learning and behavioral problems. Doctors aren't sure whether a Chiari malformation directly causes these problems or whether they're simply a way of reacting to the condition and its symptoms.
Since Chiari malformations can be caused by certain birth defects, like spina bifida, children born with these defects are usually tested to see whether they have a 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 because its symptoms 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), which uses magnets, radio waves, and computer technology to produce 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. Cine MRI is a specific type of MRI that doctors use to see whether the flow of CSF around the brain and spinal cord is abnormal.
X-rays, which produce images of bones on film and can detect bone problems caused by Chiari malformations.
Computed tomography (CT or CAT) scans, which produce pictures of bones and other body parts using X-rays and a computer. Scanning 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 and helps to determine whether the brain stem is working properly.
Somatosensory evoked potential (SSEP), a test that helps find whether messages from the brain can travel properly 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.
Most kids with Chiari malformations who don't have symptoms or any related conditions don't need treatment. They should, however, continue to see their doctors for regular checkups to make sure that their condition doesn't change.
When symptoms do happen, treatment focuses on relieving symptoms and stopping further damage to the brain and spinal cord. Doctors often recommend medicines for symptoms like headaches and neck pain. They also may recommend limiting activities that make symptoms worse.
Children with severe symptoms should be seen by a neurosurgeon, who will decide whether surgery is a good idea.
A common surgical procedure for kids with Chiari malformation is called decompression. This helps to relieve pressure on the brain and spinal cord, restore the flow of CSF, and prevent additional damage to the brain and spine. This surgery usually takes several hours and involves removing a small part of the skull and a portion of the top vertebra in the spine to reduce pressure in that area.
If a child with a Chiari malformation also has hydrocephalus, the treatment usually includes an endoscopic third ventriculostomy (ETV). In an ETV, a small hole is made in a fluid-filled chamber of the brain to divert the flow of fluid and relieve pressure in the brain. In rare cases, a shunt or tube might be implanted in the brain to drain the fluid.
Many kids with this condition do not have health problems. Those with mild symptoms usually find that medicines provide enough relief for them to lead normal lives. Usually, symptoms don't get worse and surgery isn't necessary for kids with milder forms.
For kids who do have surgery, the outcome may depend on how severe the symptoms were and how long they existed before the surgery. Kids who only had symptoms for a brief period before surgery are more likely to have their symptoms relieved by surgery than those who had symptoms for many years.