What is a Chiari Malformation?

What is a Chiari Malformation?

A Chiari malformation is a structural abnormality in which the cerebellum is pushed down through a large opening at the base of the skull and into the upper spinal canal. This can create pressure on the brain and spinal cord, restricting the flow of cerebrospinal fluid (CSF) between the head and spine. 

Chiari malformation treatment options depend on the type and severity of the condition, and include ongoing monitoring for children with no symptoms. Surgery may be needed for children with more severe Chiari malformations.

Types of Chiari Malformation


Chiari malformation types are classified according to the severity of the condition and the part of the brain. Some people with Chiari malformation have no signs or symptoms and do not need treatment, but depending on the type and severity, Chiari malformation can cause serious problems.

Types of Chiari malformation include:

  • Chiari malformation Type I – Though it’s the most common type of Chiari malformation, type l is still quite rare. It is estimated that fewer than 1% of the general population and about 3.6% of children have the condition. It occurs when the back of the brain, called the cerebellar tonsils, descends below the opening at the base of the skull (foramen magnum). Type I malformations may go unnoticed until symptoms arise, typically in adolescence or early adulthood. Some patients with Type I malformation can develop a cyst in the spinal cord.
  • Chiari malformation Type II – In this type of malformation, both the cerebellar tonsils and brainstem descend below the foramen magnum. Symptoms of Type II usually appear during childhood and are more severe than in Type l. Signs of breathing and eating difficulties may be noticed at birth.
  • Chiari malformation Type III – Type lll is a rare and serious condition in which the back of the brain protrudes out of an opening in the back of the skull area because the skull did not completely close during fetal development. Symptoms appear in infancy, and babies may have additional severe neurological problems such as seizures.
  • Chiari malformation Type IV - Another rare type of Chiari malformation that occurs when the cerebellum (back of the brain) does not develop entirely during pregnancy.

Signs & Symptoms of Chiari Malformation


Chiari malformation symptoms may vary and depend on the type of malformation. Type I Chiari malformation symptoms typically appear in adolescence or early adulthood, as the skull and tissues of the neck mature.

Type I symptoms include:

  • Headache that gets worse with exertion, including exercise, coughing, sneezing, or laughing
  • Stiffness or pain at the base of the neck or back of the head area
  • Dizziness
  • Tingling or numbness, usually in the hands (and rarely in the legs)
  • Unsteady gait
  • Loss of fine motor skills
  • Difficulty swallowing or choking on liquids
  • Spine deformity (scoliosis)

Types I to IV - Infants with any type of Chiari malformation may show the following symptoms:

  • Difficulty swallowing
  • Gagging or vomiting
  • Irritability during feeding
  • Excessive drooling
  • A weak cry
  • Arm weakness
  • Stiff neck
  • Problems breathing
  • Developmental delays
  • Failure to gain weight

The symptoms of a Chiari malformation may resemble other medical conditions. An accurate and early diagnosis is essential to ensure proper treatment by pediatric neurosurgeons who specialize in Chiari malformations and other complex congenital conditions.

What Causes Chiari Malformations?


The exact cause of Chiari malformations is unknown. They may result from part of the skull not being large enough for the brain, and genetic factors may be involved, but more studies are needed to learn possible causes.

Risk Factors

Risk Factors

Currently, there are no known risk factors for Chiari malformation. The condition can sometimes run in families, but more genetic studies are needed to learn about this risk factor.



Chiari malformation can sometimes lead to serious complications. The complications associated with this condition include:

  • Hydrocephalus a condition in which excess cerebrospinal fluid (CSF) accumulates of the brain, which increases the pressure inside of the head and may require treatment to drain the excessive fluid
  • Spina bifida - Children with Chiari malformation type II often have a severe spina bifida called myelomeningocele. With this condition, a defective portion of the spinal cord and the surrounding structures develop outside the body. It can cause serious conditions such as muscle weakness, scoliosis, and paralysis.
  • Syringomyelia may develop in some people with Chiari malformation. In syringomyelia, a cavity or cyst (syrinx) forms within the spinal column and can damage the spinal cord if not treated properly
  • 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.
Get Care

Trust NewYork-Presbyterian for Chiari Malformation Care

At NewYork-Presbyterian, our experts provide advanced and comprehensive care for children with Chiari malformations and other complex congenital malformations of the central nervous system. Learn about pediatric neurological conditions and treatments for Chiari malformations. Contact us today to schedule an appointment.