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.


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.

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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.

Chiari malformation care at Mayo Clinic

Oct. 20, 2023
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