Chiari malformation


Chiari malformation (kee-AH-ree mal-for-MAY-shun) is a condition in which brain tissue extends into the spinal canal. It occurs when part of the skull is misshapen or smaller than is typical. The skull presses on the brain and forces it downward.

Chiari malformation is not common, but increased use of imaging tests has led to more diagnoses.

Health care professionals group Chiari malformation into three types. The type depends on the anatomy of the brain tissue that is pushed into the spinal canal. The type also depends on whether there are developmental changes of the brain or spine.

Chiari malformation type 1 develops as the skull and brain are growing. Symptoms may not occur until late childhood or adulthood. The pediatric forms of Chiari malformation are type 2 and type 3. These types are present at birth, which is known as congenital.

Treatment of Chiari malformation depends on the type and the symptoms. Regular monitoring, medicines and surgery are treatment options. Sometimes no treatment is needed.

Chiari malformation


Many people with Chiari malformation have no symptoms and don't need treatment. They learn they have Chiari malformation only when tests are performed for unrelated conditions. But some types of Chiari malfunction can cause symptoms.

The more common types of Chiari malformation are:

  • Type 1
  • Type 2

These types are less serious than the rarer pediatric form, type 3. But symptoms still can disrupt life.

Chiari malformation type 1

In Chiari malformation type 1, symptoms usually appear during late childhood or adulthood.

Bad headaches are the classic symptom of Chiari malformation. They generally occur after sudden coughing, sneezing or straining. People with Chiari malformation type 1 also can experience:

  • Neck pain.
  • Unsteady walk and trouble with balance.
  • Poor hand coordination.
  • Numbness and tingling of the hands and feet.
  • Dizziness.
  • Trouble swallowing. This sometimes happens with gagging, choking and vomiting.
  • Speech changes, such as hoarseness.

Less often, people with Chiari malformation may experience:

  • Ringing or buzzing in the ears, known as tinnitus.
  • Weakness.
  • Slow heart rhythm.
  • Curvature of the spine, known as scoliosis. The curvature is related to spinal cord impairment.
  • Trouble with breathing. This includes central sleep apnea, which is when a person stops breathing during sleep.

Chiari malformation type 2

In Chiari malformation type 2, a greater amount of tissue extends into the spinal canal compared with that in Chiari malformation type 1.

Symptoms can include those related to a form of spina bifida called myelomeningocele. Chiari malformation type 2 nearly always occurs with myelomeningocele. In myelomeningocele, the backbone and the spinal canal don't close properly before birth.

Symptoms may include:

  • Changes in breathing pattern.
  • Trouble swallowing, such as gagging.
  • Quick downward eye movements.
  • Weakness in the arms.

Chiari malformation type 2 is usually noted with ultrasound during pregnancy. It also may be diagnosed after birth or in early infancy.

Chiari malformation type 3

Chiari malformation type 3 is the most serious type of the condition. A portion of the lower back part of the brain, known as the cerebellum, or the brainstem extend through an opening in the skull. This form of Chiari malformation is diagnosed at birth or during pregnancy with an ultrasound.

Chiari malformation type 3 causes brain and nervous system issues and has a higher rate of death.

When to see a doctor

See a health care professional if you or your child has any of the symptoms that may be associated with Chiari malformation.

Many symptoms of Chiari malformation also can be caused by other conditions. A full medical evaluation is important.


Chiari malformation type 1 occurs when part of the skull is too small or is misshapen. This part of the skull contains the area of the brain called the cerebellum. The skull puts pressure on and crowds the brain. As a result, the lower part of the cerebellum known as the tonsils are pushed into the upper spinal canal.

Chiari malformation type 2 is nearly always associated with a form of spina bifida called myelomeningocele.

When the cerebellum is pushed into the upper spinal canal, it can interfere with the usual flow of cerebrospinal fluid that protects the brain and spinal cord. Cerebrospinal fluid can build up in the brain or spinal cord. Or it can cause signals transmitted from the brain to the body to be blocked.

Also, the pressure from the cerebellum on the spinal cord or lower brainstem can cause symptoms.

Risk factors

There's evidence that Chiari malformation runs in some families. However, research into a possible hereditary component is still in its early phase.


In some people, Chiari malformation may have no symptoms and they don't need treatment. In others, Chiari malformation gets worse over time and leads to serious complications. Complications may include:

  • Hydrocephalus. Hydrocephalus occurs when too much fluid builds up in the brain. This can cause trouble with thinking. People with hydrocephalus may need a flexible tube called a shunt placed. The shunt diverts and drains excess cerebrospinal fluid to a different area of the body.
  • Spina bifida. Spina bifida is a condition in which the spinal cord or its covering isn't fully developed. Part of the spinal cord is exposed, which can cause serious conditions such as paralysis. People with Chiari malformation type 2 usually have a form of spina bifida called myelomeningocele.
  • Syringomyelia. Some people with Chiari malformation also develop a condition called syringomyelia. In people with this condition, a cavity or cyst called a syrinx forms within the spinal column. As the syrinx grows, it can press on the nerves and cause pain, weakness and stiffness.
  • Tethered cord syndrome. In this condition, the spinal cord attaches to the spine and causes the spinal cord to stretch. This can cause serious nerve and muscle damage in the lower body.


To diagnose Chiari malformation, your health care professional reviews your medical history and symptoms and does a physical exam.

Imaging tests can help diagnose the condition and determine its cause. Tests may include:

  • Magnetic resonance imaging (MRI). An MRI is often used to diagnose Chiari malformation. An MRI uses powerful radio waves and magnets to create a detailed view of the body.

    This safe, painless test produces detailed 3D images of structural differences in the brain that may be contributing to symptoms. It also can provide images of the cerebellum and determine whether it extends into the spinal canal.

    An MRI can be repeated over time, and it can be used to monitor the condition.

  • Computerized tomography (CT) scan. The health care professional may recommend other imaging tests such as a CT scan.

    A CT scan uses X-rays to obtain cross-sectional images of the body. This can help to reveal brain tumors, brain damage, bone and blood vessel problems, and other conditions.


Treatment for Chiari malformation depends on your condition. If you have no symptoms, your health care professional may recommend no treatment other than monitoring with regular exams and MRIs.

When headaches or other types of pain are the primary symptom, your health care professional may recommend pain medicine.

Reducing pressure with surgery

Chiari malformation that causes symptoms is usually treated with surgery. The goal is to prevent more damage to the central nervous system. Surgery also can ease or stabilize symptoms.

Surgery can reduce pressure on the cerebellum and spinal cord and restore the usual flow of spinal fluid.

The most common surgery for Chiari malformation is called posterior fossa decompression. Surgery involves removing a small section of bone in the back of the skull. This relieves pressure by giving the brain more room.

During surgery, the covering of the brain called the dura mater may be opened. Also, a patch may be sewn in place to enlarge the covering and provide more room for the brain. This patch may be an artificial material, or it could be tissue harvested from a different part of the body.

Your surgeon also may remove a small portion of the spinal column to relieve pressure on the spinal cord and allow more space.

The surgical technique may vary, depending on whether you have a fluid-filled cavity called a syrinx or if you have fluid in your brain, known as hydrocephalus. If you have a syrinx or hydrocephalus, you may need a tube called a shunt to drain the excess fluid.

Surgical risks and follow-up

Surgery involves risks, including the possibility of infection, fluid in the brain, cerebrospinal fluid leakage or trouble with wound healing. Talk about the risks and benefits with your surgeon when deciding whether surgery is the most appropriate treatment for you.

The surgery reduces symptoms in most people. But if nerve injury in the spinal canal has already occurred, this procedure won't reverse the damage.

After the surgery, you'll need regular follow-up exams with your health care professional. This includes regular imaging tests to assess the outcome of surgery and the flow of cerebrospinal fluid.

Preparing for an appointment

You're likely to start by seeing your health care professional. However, when you call to set up an appointment, you may be referred to a doctor trained in brain and nervous system conditions, known as a neurologist.

Because appointments can be brief, and because there's often a lot to talk about, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment and know what to expect from your doctor.

What you can do

  • Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance.
  • Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment. For example, although your primary complaint may be headaches, tell your health care professional about any changes in your vision, speech or coordination.
  • Write down key personal information, including any major stresses and recent life changes.
  • Make a list of your key medical information, including other conditions you're being treated for and the names of the medicines that you're taking.
  • Take a family member or friend along, if possible. Sometimes it can be difficult to recall all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your health care professional.

Prepare a list of questions so that you can make the most of your limited time during your appointment. List your questions from most important to least important in case time runs out. For Chiari malformation, some basic questions to ask include:

  • What is likely causing my symptoms or condition?
  • Other than the most likely cause, what are possible causes for my symptoms or condition?
  • What kinds of tests do I need?
  • Do I need treatment?
  • If you don't think I need to be treated now, how will you monitor me for changes in my condition?
  • If you recommend surgery, what should I expect from my recovery?
  • What is the risk of complications from surgery?
  • What is my long-term prognosis after surgery?
  • I have other health conditions. How can I best manage them together?
  • Are there any restrictions that I need to follow?
  • Should I see a specialist? What will that cost, and will my insurance cover seeing a specialist?
  • Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

In addition to the questions that you've prepared, don't hesitate to ask questions during your appointment if you don't understand something.

What to expect from your doctor

Your health care professional is likely to ask you some questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your health care professional may ask:

  • When did you first begin experiencing symptoms?
  • Have your symptoms been continuous or occasional?
  • If you experience head and neck pain, is it made worse by sneezing, coughing or straining?
  • How bad is your head and neck pain?
  • Have you noticed any change in your coordination, including problems with balance or with hand coordination?
  • Do your hands and feet feel numb or do they tingle?
  • Have you developed any trouble swallowing?
  • Do you experience episodes of dizziness or faintness? Have you ever passed out?
  • Have you developed any problems with your eyes and ears, such as blurred vision or a ringing or buzzing in your ears?
  • Have you had problems with bladder control?
  • Has anyone ever noticed that you stop breathing during sleep?
  • Have you been taking pain relievers or using other approaches to relieve your discomfort? Does anything seem to work?
  • Do you have any additional symptoms, such as hearing loss, fatigue, or changes in your bowel habits or appetite?
  • Have you been diagnosed with any other health conditions?
  • Has anyone in your family been diagnosed with Chiari malformation?

Content From Mayo Clinic Updated: 10/19/2023
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