Chiari Malformation

A Chiari malformation is a structural abnormality in your skull that causes part of your brain to move into your spinal canal. You may have mild or severe symptoms or no symptoms at all. It usually causes headaches and difficulty with balance and coordination, as it affects your cerebellum. Surgery may help.


A Chiari malformation where the cerebellum extends into the spinal canal.
A Chiari malformation occurs when part of your brain (cerebellum) extends into your spinal canal.

What is a Chiari malformation?

A Chiari malformation is a growth abnormality where brain tissue in the lower back of your skull extends into your spinal canal (the base of your skull).

It happens because of a structural problem like a smaller-than-expected skull size. If you don’t have enough room in your skull, part of your brain, specifically your cerebellum, will grow downward where there’s extra space in an opening at the base of your skull — called the foramen magnum.

Your cerebellum is the part of your brain that helps with your muscle movements, posture, balance, speech and coordination. It causes symptoms that affect the function of this part of your brain, like loss of balance.

This growth abnormality causes your brain to press against the base of your skull. It blocks the flow of cerebrospinal fluid. This fluid cushions your brain and spinal cord, circulates nutrients and chemicals, and removes waste products.

What are the types of Chiari malformation?

There are five types of Chiari malformations including:

  • Chiari malformation type 0: Type 0 is very rare. In this type, there are little to no parts of your cerebellum in the hole at the base of your skull (foramen magnum) but there is crowding at that level. Symptoms occur because of an abnormal flow of cerebrospinal fluid near the base of your skull.
  • Chiari malformation type I: Type I occurs when the lower part of your cerebellum extends into the hole (foramen magnum) at the base of your skull. Your spinal cord normally passes through this hole. Type I is the most common form of Chiari malformation. People with type I may not have any symptoms or they may not develop symptoms until they’re adolescents or adults.
  • Chiari malformation type II: Type II occurs during brain and spine development in the uterus. With a type II malformation, your cerebellum and brain stem grow abnormally and cause pressure inside of your skull. Type II usually happens with a severe form of spina bifida called myelomeningocele. Myelomeningocele occurs when the backbone and spinal canal don’t close properly before a baby is born. Surgery closes the spine after birth, but paralysis can occur.
  • Chiari malformation type III: This is rare and the most severe of the Chiari malformations. It occurs when some of your cerebellum and brain stem extend through an abnormal opening in the back of your skull (not the foramen magnum). In addition, some of the membranes that surround your brain or spinal cord extend through the opening. This malformation results in swelling at the back of your skull called an encephalocele. Type III causes severe, life-threatening symptoms and they appear during childhood. Children with type III have neurological problems, learning delays and seizures. It often requires surgery.
  • Chiari malformation type IV: Chiari malformation type IV is rare and happens when your cerebellum itself is underdeveloped or has parts missing. This type is severe and usually life-threatening in infants.

How common is a Chiari malformation?

Studies suggest that Chiari malformations occur in about 1 in every 1,000 people in the United States. Because some people don’t have any symptoms or don’t show them until adolescence or adulthood, the condition may be more common.


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Symptoms and Causes

What does a Chiari malformation feel like?

You may experience the following symptoms if you have a Chiari malformation.

  • Headaches or a throbbing, stabbing or sharp pain in the back of your head, neck or shoulders that gets worse after coughing or sneezing.
  • Difficulty with balance and coordination.
  • Dizziness and vertigo.
  • Weak muscles.
  • Numbness in your arms or legs or a burning sensation in your fingers, toes or lips.
  • Feeling like your heart misses a beat (palpitations).
  • Difficulty falling asleep (insomnia) and feeling tired all the time (chronic fatigue).

What are the symptoms of a Chiari malformation?

Common symptoms of Chiari malformations include:

Symptoms vary from person to person and range from no symptoms to mild to severe symptoms. In some people, symptoms are present at birth. In others, symptoms appear in late childhood or adulthood. Symptoms may also get better or worse at different points in time.


What causes a Chiari malformation?

A Chiari malformation happens when the lower back part of your brain pushes through your spinal canal or the foramen magnum, where your brain and spinal cord meet. A structural growth abnormality (a smaller-than-expected size in the area where your cerebellum sits) in your brain and spinal cord causes pressure in this part of your brain. The pressure makes your cerebellum grow in a different than expected location. This happens during fetal development.

Chiari malformations are almost always present at birth (congenital), though symptoms may not develop until later in life. This is usually the result of a genetic change (mutation) that you inherit from your biological family or it happens randomly after conception.

Very rarely, a Chiari malformation can develop in someone who wasn’t born with the condition. In these cases, the skull or spinal cord might change shape due to:

A Chiari malformation may happen in addition to an underlying health condition like:

What are the risk factors for a Chiari malformation?

A Chiari malformation can affect anyone. You may be more likely to develop a Chiari malformation if someone in your biological family has the condition.

What are the complications of a Chiari malformation?

Chiari malformation can cause severe health issues and developmental delays. Complications may include:

  • Hydrocephalus: This life-threatening condition occurs when cerebrospinal fluid (CSF) builds up in your brain. Hydrocephalus happens when the CSF can’t drain. As CSF builds up, it causes pressure within your skull. This can lead to problems with cognitive functioning and a misshapen head. It’s life-threatening if left untreated. This complication is most often seen in Chiari malformation type II.
  • Syringomyelia and hydromyelia: When CSF isn’t flowing properly between your brain and spine, CSF can accumulate in your spine. This fluid buildup can cause damage to your spinal cord and result in symptoms like movement and balance problems, pain, muscle weakness, muscle spasms, numbness, a decreased sensation to hot and cold, and loss of bladder and bowel control.
  • Tethered cord syndrome: Children born with myelomeningocele (a severe form of spina bifida) are at an increased risk of developing tethered cord syndrome as they grow. This occurs when their spinal cord attaches to their spine due to scarring after closure surgery. With tethered cord syndrome, there can be slow and progressive nerve damage that affects the muscles of their lower body and legs. It can also affect their bowel and bladder function.

In addition, symptoms of a Chiari malformation can affect your mood, especially if you experience insomnia or severe headaches. Some people may develop depression. If this condition affects your mood, talk to your healthcare provider or a mental health professional.


Diagnosis and Tests

How is a Chiari malformation diagnosed?

A healthcare provider will diagnose a Chiari malformation after a complete physical exam. Your provider will test your movement, balance and the sensations in your hands and feet. In addition, they’ll look for memory problems, learning challenges and developmental delays among children.

To confirm a diagnosis, a healthcare provider will order imaging tests to see a detailed image of your brain and spinal cord. Imaging tests may include:

  • Magnetic resonance imaging (MRI): This imaging test can show soft tissues and bones. It helps your healthcare provider see your brain, spinal cord and cerebrospinal fluid. MRI can show the extent that the cerebellum extends into your spinal canal.
  • Cine MRI: This test is similar to a traditional MRI, but it allows your doctor to see the flow pattern of cerebrospinal fluid (CSF) around the base of your skull.
  • Computed tomography (CT): A CT scan helps detect problems in bones at the base of your skull and spinal column.
  • X-ray: X-rays check for bone abnormalities in your skull and neck.

Sometimes, Chiari malformations appear on prenatal ultrasounds before a fetus is born. An ultrasound is an imaging test that uses sound waves to produce pictures of soft tissues.

If you don’t experience symptoms of a Chiari malformation, you might receive this diagnosis if you get imaging tests for another unrelated reason.

Management and Treatment

How is Chiari malformation treated?

Your healthcare provider will make a treatment plan based on the severity of your symptoms. If you don’t have symptoms, you don’t need treatment. Your provider will monitor your health with regular MRIs.

Treatment for mild symptoms like a headache or neck pain may include:

  • Taking pain medications or medications to help you manage your symptoms.
  • Participating in massage therapy or physical therapy.
  • Limiting your physical activities like heavy lifting.
  • Using devices like hearing aids or glasses to help with hearing or vision loss.

Chiari malformation surgery

Severe Chiari malformation cases may need surgery. Surgical procedures may include:

  • Craniectomy: Your surgeon will remove a piece of your skull to relieve pressure on your brain and help cerebrospinal fluid flow.
  • Posterior fossa decompression: This is the most common procedure to treat a Chiari malformation. Your surgeon relieves pressure on your brain, giving it more room, by removing a part of the back of the skull called the posterior fossa.
  • Laminectomy: Depending on how severe the Chiari malformation is, your surgeon may remove a small portion of bones covering your spinal column to restore the flow of cerebrospinal fluid and allow more room for your spinal cord.
  • Duraplasty: In this decompression surgery, your surgeon opens the dura (a membrane on the outside of your brain). Then, your surgeon sews in a patch to make the membrane larger so your brain has more room. This procedure enlarges the area and relieves pressure on your brain.
  • Electrocautery: To create more room and allow the cerebrospinal fluid to drain, surgeons may apply a small amount of electricity to shrink a small part of your brain called the cerebellar tonsils. The cerebellar tonsils retract without causing brain or nerve damage.
  • Shunt placement: Your surgeon will implant a shunt or tube in your skull to collect excess CSF if you have hydrocephalus. The fluid drains away from your skull and brain and collects in another part of your body.

Are there side effects of the treatment?

Your healthcare provider will discuss the side effects of treatment before you begin so you can make an informed decision about your health. Every surgery comes with possible risks. Surgery around your brain and skull is high risk due to the location of the incision and procedure being near your brain. Repeat surgeries might be necessary as you age.

How soon after treatment will I feel better?

Depending on what treatment you and your healthcare provider choose, you may find relief from mild symptoms soon after taking pain medication or participating in therapy. It could take several weeks to months before you heal from surgery. You may notice your symptoms go away or reduce significantly after surgery.


Can a Chiari malformation be prevented?

There’s no known way to prevent a Chiari malformation.

If you plan on becoming pregnant, talk to your healthcare provider about ways to maintain good health. Your provider may recommend you regularly take vitamins like folic acid to lower your risk of having a child diagnosed with spina bifida. Your provider may suggest genetic testing so you can understand your risk of having a child with a genetic condition.

Outlook / Prognosis

Is a Chiari malformation serious?

A Chiari malformation can be very serious in some cases, but not all. In most cases, babies are born with a Chiari malformation. However, symptoms aren’t always present, and a diagnosis won’t happen until late childhood or adulthood when a healthcare provider orders an imaging test for another unrelated reason.

Although there isn’t a cure for a Chiari malformation, treatment like surgery can help manage your symptoms to help you feel better and prevent life-threatening complications.

What’s the outlook for a Chiari malformation?

Your outlook varies depending on the severity and type of Chiari malformation. It’s important to work closely with your healthcare provider and care team, who can monitor your symptoms and determine the right treatment plan for you.

What is the life expectancy of someone with a Chiari malformation?

If you don’t have symptoms or you have mild symptoms after a Chiari malformation diagnosis, you’ll likely have a normal life expectancy. Severe symptoms and certain types of Chiari malformation can be fatal. Talk to your healthcare provider about what to expect after a diagnosis.

Living With

When should I see a healthcare provider?

Visit a healthcare provider if you experience symptoms of a Chiari malformation or if your symptoms get worse. If you have a child with a Chiari malformation and they miss developmental milestones for their age, talk to their provider. After surgery, contact your healthcare provider if you show signs of an infection like severe pain, swelling or your surgical wound not healing.

Contact local emergency services or 911 if you or a loved one have a seizure for the first time.

What questions should I ask my doctor?

  • What type of Chiari malformation do I have?
  • What type of treatment do you recommend?
  • How often do I need imaging tests to monitor the condition?
  • Do you recommend surgery?
  • Are there side effects of the treatment?
  • Will my future children also have this condition?

A note from Cleveland Clinic

A Chiari malformation affects each person differently. You may not have any symptoms or they could be mild and have little interference with your daily routine. Others may experience severe, often disabling symptoms that require surgery. Treatment is available to reduce your symptoms and prevent life-threatening complications for certain types of the condition. If your symptoms don’t improve, get worse or you experience problems like an infection after surgery, contact your healthcare provider.

Medically Reviewed

Last reviewed on 10/02/2023.

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