Spine · Conditions

Chiari Malformation: Definition, Causes, Risk Factors and Complications

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Chiari Malformation

Chiari Malformation is a condition in which brain tissue may protrude through an opening in the base of the skull and into the spinal cord. This condition may happen when part of the skull is too small or has an unusual shape, pressing on the brain tissue and forcing it downward.


Type I Chiari Malformation occurs when the brain and skull are at their growing stage. Thus, the symptoms and signs do not happen until the latter part of childhood or adulthood.

Type II Chiari Malformation, which is the most common form, happens at birth and is described consequently as being congenital. Treatment depends on the seriousness of the condition, its form, and the symptoms related to it. Some of the possible options for treatment are medications and in some cases surgery.

Type III Chiari Malformation is one of the most rare and serious types of this disorder. It happens when a portion of the brain’s stem protrudes into the spinal cord. This type of Chiari Malformation is usually discovered at birth or during an ultrasound while the mother is pregnant. This condition usually causes complex neurological defects.

Type IV Chiari Malformation is also known as Cerebellar Hypoplasia. This rare type of Chiari Malformation is characterized by a lack of cerebellar development in which the cerebellum and brain stem lie in a normal position, but portions of the cerebellum are possibly missing or underdeveloped. This condition is not compatible with life.

Doctors have identified and classified Chiari Malformation symptoms based on the anatomical make-up of the displaced tissue in the spine’s canal and whether there are abnormalities that developed in the spine or in the brain. Many individuals with Chiari Malformation do not develop symptoms and usually do not require any treatment. Their disorder is revealed only when tests are done for unrelated conditions. Depending on its type and severity, Chiari Malformation may cause numerous complications.


Type I Chiari Malformation occurs when the segment of your skull containing a piece of your cerebrum (cerebellum) is not fully developed or is twisted. The lower part, or tonsils, of the cerebellum, are dislodged into the upper spinal trench.

Type II Chiari Malformation symptoms are usually associated with a type of Spina Bifida called Myelomeningocele.

At the point when the cerebellum is pushed into the upper spinal waterway, it can disrupt the normal stream of cerebrospinal liquid that flows to the cerebrum and spinal cord.

This disruptive flow of cerebrospinal liquid can prompt the blockage of brain signals transmitted to the body, or to a development of spinal liquid in the cerebrum or spinal cord.

Additionally, the weight from the cerebellum upon the spinal cord or lower brainstem can cause neurological signs or manifestations.

Chiari Malformation symptoms, may include:

  • Some structural defects in the brain and spinal cord that develop during fetal development (may be connected to genetic mutations or severe deficiency in mother's diet) that leads to Chiari Malformation symptoms.
  • Herniated cerebellum tissue may disturb the spinal fluid flow and cause additional neurological signs or symptoms.


The prevalence of Type I Chiari Malformation symptoms is approximately 1:1000 births. Females are three times more likely to be affected than men. Type II Chiari Malformation symptoms may be more prevalent in some ethnic groups.

Risk factors

There is no clear evidence of any risk factors connected to Chiari Malformation symptoms. However, some scientists suggest that Chiari Malformation is hereditary and may be observed in some predisposed families more often.


In certain individuals, Chiari Malformation may develop into a more dynamic issue and prompt genuine concerns. In others, there may be no related side effects, thus no medication is needed. The intricacies related to this condition include:

  • Hydrocephalus: A condition in which there is an abundance of fluid on the brain (hydrocephalus). This condition may require the arrangement of an adaptable tube (shunt) to redirect or deplete the excess cerebrospinal fluid.
  • Spina Bifida: Spina Bifida is a type of birth defect and occurs when the bones of the spine do not form properly around the spinal cord, thus leaving some portion of the spinal cord uncovered. Individuals with Type II Chiari Malformation often have a type of Spina Bifida called Myelomeningocele.
  • Syringomyelia: Certain individuals with Chiari Distortion additionally build up a condition called Syringomyelia which is a cyst (syrinx) that forms inside the spinal cord.
  • Tethered Cord Syndrome: Functional disorder where the spinal cord connects to the spine thus limiting its ability to stretch impairing movement.
Chiari malformation symptoms
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