What Is the Difference Between Types I and II Chiari Malformations?

Medically Reviewed on 10/27/2022
Types I and II Chiari Malformations
Chiari malformation can develop into a disease in some people and cause life-threatening problems.

Chiari I malformation, the most common type, occurs when the cerebellar tonsils, which are in the lower region of the brain, obstruct the foramen magnum.

  • Typically, this hole is only used by the spinal cord.
  • It is discovered for the first time in adolescence or adulthood, frequently by accident during a checkup for another condition.
  • Adolescents and adults with Chiari malformation, who do not initially exhibit any symptoms, may do so later in life.

In Chiari II malformation, the cerebellum and brain stem tissue both protrude into the foramen magnum. There could be a lack of or partial development of the nerve tissue that connects the two halves of the cerebellum.

  • It is a much less common type of Chiari formation.
  • Typically, type II is accompanied by myelomeningocele, a type of spina bifida that develops when the spinal canal and backbone do not fully close before childbirth
  • Myelomeningocele typically causes partial or total paralysis of the region below the spinal opening.

When compared to Chiari I, the symptoms of Chiari II are typically more severe and manifest during childhood. Infancy or early childhood are the most dangerous times for it to occur, and surgery is needed to address it. Chiari II anomalies are called Arnold-Chiari malformations.

What are Chiari malformations?

Chiari malformations are structural flaws in the cerebellum, a region of the brain that controls balance and is located at the base of the skull.

  • In a healthy individual, the cerebellum and a portion of the brain stem cover the opening in the skull where the spinal cord passes through (called the foramen magnum).
  • When a piece of the cerebellum protrudes from the foramen magnum into the upper spinal canal, it is called Chiari malformation.
  • Chiari malformations can arise when a portion of the skull is abnormally tiny or shaped, placing pressure on the brain and causing the cerebellum to descend into the spinal canal.
  • Pressure on the brain stem and cerebellum may impair their ability to control certain functions and obstruct the flow of cerebrospinal fluid, the clear fluid that surrounds and supports the brain and spinal cord.

What are the symptoms of Chiari malformation?

The severity of symptoms might range from none to mild or severe. Some people have symptoms from the moment they are born. Others get the symptoms in late childhood or adulthood. Additionally, symptoms may get better or worse with time.

Typical signs of Chiari malformation include:

  • Headache: Most people experience this symptom. Coughing, sneezing, or straining can cause a headache to start or get worse. It frequently starts toward the back of the head. Pain may radiate to the shoulder and neck region. Sharp, stabbing, or throbbing are common descriptors for pain.
  • Problems with balance and movement: Numbness in the limbs, muscle weakness, and coordination impairments can contribute to issues with fine motor skills. Chiari malformation can cause balance issues, vertigo, and dizziness.
  • Hearing and visual issues: Some persons experience tinnitus (a buzzing or ringing noise) and may experience hearing issues. Nystagmus, photophobia, double vision (diplopia), and blurred vision are other potential symptoms.
  • Difficulty drinking, eating, and speaking: Dysphagia or difficulty swallowing can happen. Babies with Chiari malformation may frequently drool, gag or vomit. They might struggle to eat, and they might not be able to put on enough weight to grow normally.
  • Scoliosis: A condition where the spine starts to curve.
  • Sleeping problems: Insomnia can develop and is occasionally brought on by headaches. Additionally, some people have sleep apnea (trouble breathing while sleeping).
  • Problems with the bladder and bowel: The Chiari malformation may cause loss of control over the bladder and bowel.
  • Other signs and symptoms: Tingling or burning in the fingers, toes, or lips; palpitations; fainting spells and persistent weariness.


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What are the causes of Chiari's malformation?

There are numerous causes of Chiari malformation, which include:

  • An anatomical flaw in the brain and spinal cord that develops during a baby's development in the womb leads to Chiari malformation. Researchers have suggested that the structural abnormality in the skull, which is smaller than usual in the region where the cerebellum is located, causes the crowding and pressure that force the brain through the foramen magnum, which connects the brain and spinal cord.
  • In some instances, Chiari malformations could be inherited (passed down through families).
  • According to several researchers, the absence of some nutrients during pregnancy could be a factor.
  • Chiari abnormalities are virtually always present at birth though symptoms may not appear for several years. In extremely rare cases, a person who was not born with the condition can develop a Chiari malformation. Tumors, abnormalities in the spine, or hematomas may cause the skull or spinal cord to change shape in various circumstances.

What are the complications of Chiari malformation?

Chiari malformation can evolve into a disease in some people and cause life-threatening problems. In some cases, there could be no corresponding symptoms, in which no treatment is required.

The following are some of the issues this disorder may cause:

  • Hydrocephalus: A condition where extra fluid builds up inside the brain. A flexible tube (shunt) is inserted to redirect and drain the cerebrospinal fluid to another location of the body.
  • Spina bifida: A disorder in which the spinal cord or its covering is not fully grown. The spinal cord is partially exposed, which can result in catastrophic diseases, including paralysis. Spina bifida or myelomeningocele is typically present in individuals with Chiari malformation type II.
  • Syringomyelia: A cyst (syrinx) originates inside the spinal column.
  • Tethered cord syndrome: The spinal cord stretches because of its attachment to the spine, which may cause serious nerve and muscle damage in the lower body.

How is Chiari malformation treated?

Following the severity of the symptoms, the doctor will develop a treatment plan.

Medical management includes routine physical exams and diagnostic tests to track the growth and development of the brain, spinal cord, skull, and backbones.

Surgery could be necessary for some forms of Chiari malformations to help drain extra cerebral spinal fluid from the brain or relieve increased pressure in the head or neck region. Severe Chiari malformations could be fatal.

Medically Reviewed on 10/27/2022
Image Source: iStock image

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Chiari Malformation. https://www.webmd.com/brain/chiari-malformation-symptoms-types-treatment

Chiari I Malformation. https://kidshealth.org/en/parents/chiari.html

Chiari Malformation Fact Sheet. https://www.ninds.nih.gov/chiari-malformation-fact-sheet

What is Chiari Malformation? https://www.stanfordchildrens.org/en/service/chiari-malformation/what-is-chiari-malformation

Chiari Malformation. https://my.clevelandclinic.org/health/articles/6008-chiari-malformation