Conditions & Treatments

Chiari Malformation

A Chiari malformation is a congenital defect in the area of the back of the head where the brain and spinal cord connect.

Chiari Malformation Type I in Children

What is a Chiari malformation?

A Chiari malformation (CM) is a problem with how the brain sits in the skull. The brain normally sits fully inside the skull. With a Chiari malformation, the lower part of the brain (cerebellum) dips down through a normal opening (foramen magnum) at the bottom of the skull. In some cases, more brain tissue also dips down through this opening. This puts pressure on parts of the brain and spinal cord, and can cause mild to severe symptoms. These can include head or neck pain and trouble with balance or movement. In most cases, the problem is present at birth (congenital). 

There are 3 types of Chiari malformations:

  • Type I (CM-I).  This is the most common type. Part of the cerebellum dips down through the bottom of the skull. This type is most often congenital (also called primary CM), but is often not found until a child is a teen or young adult. In rare cases, this type may also develop later in life. This is known as acquired or secondary CM. It occurs from a loss of spinal fluid. This can happen because of an injury, contact with harmful substances, or an infection.

  • Type II (CM-II or Arnold-Chiari malformation). Part of the cerebellum and the brainstem dip down through the bottom of the skull. This is most often seen in babies born with spinal myelomeningoceles or spina bifida. A myelomeningocele is when a part of the spinal cord and backbone (spine) develop outside the body. A common problem with Type II CM is too much fluid on the brain (hydrocephalus). The excess fluid causes the pressure in the brain to increase and the skull bones to expand beyond normal size.

  • Type III (CM-III). This type is the most severe. The cerebellum, brain stem, and possibly other parts of the brain dip down through the bottom of the skull. In rare cases, the brain and brain covering may poke out through the back of the head or neck. A baby with Type III CM may not live long. Children who do will have severe neurologic problems such as mental impairment, seizures, and muscle problems.

What causes a Chiari malformation type I?

The exact cause of a congenital Chiari malformation type I is not known. A problem during fetal growth may cause the defect. It may be caused by contact with harmful substances during pregnancy. Or it may be linked with genetic problems that run in families.                                                                                              

An acquired Chiari malformation type I happens to a person after birth. It is caused by excess leaking of spinal fluid from the lower back (lumbar) or chest (thoracic) areas of the spine. This can happen because of an injury, contact with harmful substances, or an infection.

What are the symptoms of a Chiari malformation type I?

Your child may not have any symptoms. Or symptoms may develop slowly over time. Most children don't have symptoms until they are teens or young adults.

The most common symptoms are headaches or pain in the back of the head or neck. The headaches and pain are made worse by coughing, laughing, or sneezing.

Your child may also have other symptoms of a Chiari malformation type I, such as:

  • Hoarseness or  trouble speaking

  • Trouble swallowing

  • Rapid, back and forth eye movements (nystagmus)

  • Periods of not breathing during sleep (sleep apnea)

  • Weakness or abnormal movements

  • Trouble with balance

  • Abnormal reflexes

  • Abnormal shape of the spine (scoliosis)

Your child may also have a pocket of fluid in the spinal cord or brain stem. This is called a syrinx. A syrinx can cause trouble walking or pain in the arms or legs.                                                                                                                                                                           

How is a Chiari malformation type I diagnosed?

In a child with no symptoms, the defect may be found when imaging tests are done for other reasons. For a child with symptoms, the health care provider will ask about your child's medical history and give your child a physical exam. He or she may refer your child to a specialist.

Imaging tests are done to detect a Chiari malformation type I. Your child may have 1 or more of these tests:

  • MRI. This test uses large magnets and a computer to make detailed pictures of the inside of the body. In some cases, a special dye is injected into a vein for the test. This dye helps show organs more clearly.

  • CT scan.This test uses a series of X-rays and a computer to create detailed pictures of the inside of the body. A CT scan is more detailed than a regular X-ray.

How is a Chiari malformation type I treated?

Your child may be treated by neurologists and neurosurgeons. These are experts in brain and spinal cord problems. Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.

  • With no symptoms. Your child’s health may be watched closely. This may include frequent physical exams and MRI tests. Your child’s health care provider may advise surgery to prevent problems.

  • With symptoms. Your child's health care provider may prescribe medicines to reduce pain. Or he or she may advise decompression surgery. This is done to relieve pressure on the brain, or to restore the flow of spinal fluid.

  • With few or no symptoms, but a syrinx. Your child's health care provider may suggest close monitoring of the defect with a special type of MRI called cine phase contrast. This helps look for blocked spinal fluid flow. Your child may need surgery, based on the MRI results or if symptoms get worse.

  • With signs of sleep apnea. Your child may need a sleep study. In this test, your child will be monitored during sleep to look for problems. A sleep study can also help the health care provider decide on additional treatment.

What are the complications of a Chiari malformation type I?

Complications of a Chiari malformation type I can include:

  • Long-term pain

  • Development of syrinx

  • Permanent damage to muscles or nerves

  • Paralysis

Carefully watching for changes in your child’s health can help prevent complications. This helps to make sure that treatment is done early.                                                              

How is a Chiari malformation type I managed?

It is hard for health care providers to predict how a Chiari malformation type I will affect a child’s long-term health. Your child may not have any changes caused by the defect. Or he or she may have worsening neurological problems. Your child’s health will be closely watched. This will include with frequent physical exams and imaging tests such as MRI. There is ongoing research as to how to best manage Chiari malformations.

When should I call my child's health care provider?

Call your child's health care provider if you notice any changes in your child. Be sure to call if you notice problems with:

  • Breathing

  • Swallowing

  • Feeding

  • Speaking

  • Walking or moving

Key points about Chiari malformation type I

  • With a Chiari malformation, the lower part of the brain dips down through a normal opening at the bottom of the skull. In some cases, more brain tissue also dips down through this opening.

  • In most cases, the problem is present at birth (congenital). 

  • There are 3 types of Chiari malformations. Type I is the most common type.

  • The most common symptoms are headaches or pain in the back of the head or neck. The headaches and pain are made worse by coughing, laughing, or sneezing.

  • Your child may also have a pocket of fluid in the spinal cord or brain stem. This is called a syrinx.

  • Imaging tests are done to detect a Chiari malformation type I. Your child may have an MRI or a CT scan.

  • Treatments include careful watching, surgery, and frequent exams and tests.

  • Carefully watching for changes in your child’s health can help prevent complications. This helps to make sure that treatment is done early.

  • Call your child’s health care provider if you noticed changes in your child’s health. This can help prevent complications.

Treatment Programs


Massachusetts General Hospital understands that a variety of factors influence patients' health care decisions. That's just one reason why we're dedicated to ensuring patients understand their diagnosis and treatment options. Because a single option might not serve all patients, we offer a wide range of coordinated treatments and related services across the hospital. Patients should consult with their primary care doctor or other qualified health care provider for medical advice and diagnosis information.

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MassGeneral Hospital for Children

  • Pediatric Neurosurgery
    The Pediatric Neurosurgery service at MassGeneral Hospital for Children diagnoses and treats all neurosurgical conditions of infants, children and adolescents, with special expertise in the management of pediatric brain tumors, hydrocephalus, spinal cord disorders, Chiari malformations, craniosynostosis, AVM's and epilepsy surgery.
Department of Neurosurgery

  • Neurosurgical Spine Service
    The Neurosurgical Spine Service at Massachusetts General Hospital specializes in neurosurgical treatment of the entire spectrum of spine disorders, providing services from diagnosis through surgery and rehabilitation.

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