What is a chiari malformation?

Chiari malformations (CMs) are structural defects in the base of the skull and the cerebellum, the part of the brain that controls balance.

This defect can cause part of the cerebellum to extend through the opening at the skull base, pushing the cerebellum and brain stem downward.

This places pressure on the cerebellum, which can block the flow of cerebrospinal fluid (CSF), the fluid that surrounds and protects the brain and spinal cord.


Chiari malformations are classified by their severity and the parts of the brain that protrude into the spinal canal. 

Depending on the severity, symptoms may include:

  • Dizziness
  • Muscle weakness
  • Numbness
  • Headaches
  • Hearing problems
  • Balance issues
  • Coordination problems


Chiari malformations don't always require treatment. 

When necessary, a surgical procedure called a posterior fossa decompression can relieve symptoms by:

  • Creating space for the cerebellum
  • Relieving pressure on the spinal cord
  • Restoring normal flow of CSF


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