Chiari malformation is a structural defect in the back of the skull. Children may be born with this malformation, or develop it later in childhood.
There are four types of Chiari malformations. Chiari I and II are the most common types. Chiari III and IV are extremely rare.
Doctors are not sure what causes Chiari malformations. The defect begins before birth when the base of a baby’s skull does not grow to a normal size. After birth, the skull hardens as the brain grows. This creates a mismatch between the skull size and brain size. As a result, the child’s brainstem, cerebellum and cerebellar tonsils become crowded.
Over time, the cerebellar tonsils (and sometimes the brain stem) get pushed down into the spinal canal. This blocks the flow of cerebrospinal fluid and causes symptoms.
In rare cases, a Chiari malformation occurs later in life to a child whose skull grew normally before birth. This is called acquired or secondary Chiari malformation. Causes can include an injury, exposure to a harmful substance or an infection.
Chiari I occurs when a portion of the brain called the cerebellar tonsils extends out of the skull and into the upper part of the spinal canal. This can disrupt the flow of cerebrospinal fluid. It is a little bit like what happens when a rock is sitting in the middle of a stream.
Chiari I can cause symptoms in infancy. Symptoms sometimes do not occur until late childhood or early adulthood, if at all. This condition often is diagnosed when a person has imaging tests for unrelated reasons.
Chiari II occurs when the cerebellar tonsils and the brain stem push down through the base of the skull into the upper spinal canal. Chiari II is often called Arnold-Chiari malformation. It is present at birth. Typically, it is seen in infants with myelomeningocele (a form of spina bifida) and/or hydrocephalus (a buildup of cerebrospinal fluid in the brain). It is the most common type of Chiari malformation. Almost all children with a myelomeningocele have Chiari II malformation.
Chiari III and IV are very rare and may be life-threatening. Please talk to your child’s physician for more information about these diagnoses.
A variety of problems can occur with Chiari malformations. Symptoms vary for each child.
The main symptom with Chiari I is a headache in the back of the brain. The headache can be severe. Other problems can include:
In rare cases, a child will experience sleep apnea. This is a condition in which breathing pauses during sleep.
Diagnosing Chiari I in an infant is challenging. Symptoms are not always obvious. Also, the child is not able to communicate exactly what is wrong. Common signs can include irritability, head banging and nighttime wakening.
About half of patients with a Chiari I malformation also develop a syrinx, which is sometimes called a syringomyelia or hydromyelia. A syrinx is a fluid-filled cavity in the spinal cord. It occurs when the normal flow of cerebrospinal fluid is obstructed.
A syrinx expands over time. It can injure nerve fibers in the spinal cord. It eventually can cause symptoms such as:
Chiari II is most often seen in infants with myelomeningocele, a form of spina bifida. Symptoms can include swallowing problems and slow or noisy breathing. The condition can lead to feeding problems, gagging, drooling and vomiting.
Children with a Chiari malformation sometimes have associated conditions. For this reason, it is important that they receive care from a multidisciplinary team of physicians. Team members may include doctors who specialize in pediatric neurosurgery, neurology, disorders of the ear, nose and throat, and other areas of medicine.
Patients with Chiari I may develop a syrinx, scoliosis, and/or have a tethered spinal cord.
Children with Ehlers-Danlos syndrome (EDS) may be at increased risk for Chiari I malformation. EDS is a connective tissue disorder that causes hypermobility and unstable joints.
Two serious conditions associated with Chiari II are myelomeningocele and hydrocephalus. A multidisciplinary team can help diagnose and treat these conditions.
In addition, some children with Chiari I or II have some form of sleep apnea. This is a condition in which they stop breathing temporarily during sleep. Treating the Chiari malformation may stop or lessen the sleep apnea.
A magnetic resonance imaging (MRI) test is the best way to detect a Chiari malformation. An MRI can create three-dimensional images of the brain and upper spinal cord from many angles. This helps doctors make an accurate diagnosis.
MRIs also can help physicians see whether the child has a syrinx within the spinal cord or a tethered spinal cord. Follow-up MRIs can help the medical team see whether the Chiari malformation changes or worsens over time.
Once the medical team establishes a diagnosis of Chiari malformation, other tests can be used to help evaluate the child’s condition. These include:
Treatment for Chiari I and II varies depending on many factors. These include the exact type of malformation, the progression of the structural defect and the child’s symptoms.
If your child has a syrinx in the spinal cord, the team will recommend decompression surgery. The purpose of this surgery is to relieve pressure on the brain and spinal cord.
Rarely, the medical team may recommend surgery to place a shunt. A shunt is a tube that can help establish a normal flow of cerebrospinal fluid around and behind the cerebellum.
If your child has Chiari I but does not have a syrinx or symptoms, no treatment is necessary. The medical team will perform follow-up MRI scans to monitor your child’s condition. If the malformation is causing neck pain or headache, pain-relief medication may help. If your child is experiencing swallowing issues, speech therapy may be helpful.
If the pain is severe, or your child is experiencing other symptoms that affect their quality of life, the medical team may recommend decompression surgery to relieve symptoms. Without surgery, a child will likely continue to have symptoms, which may worsen over time.
Children with Chiari II typically do not undergo surgery, unless the malformation is causing breathing and swallowing difficulties. In that case, the medical team may recommend decompression surgery.
Some children never require treatment for a Chiari malformation. Others are able to enjoy a good quality of life with the help of non-surgical therapies. These therapies may include pain-relief medicine or physical therapy.
When surgery is needed, results are often very positive. Many children are symptom-free or have significantly fewer symptoms. Follow-up care includes performing MRIs at regular intervals. These tests help doctors evaluate the results of the decompression, the response of any associated syrinx, and any scar tissue development.
In a small number of cases, a second decompression surgery may be needed.
Last Updated 10/2023
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