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Chiari Malformation

Now is your opportunity to learn a little about Chiari malformation, the different types and how and why they happen.



A Chiari malformation is a condition in which some of the brain tissue (cerebellar tonsils, cerebellum, brain stem and/or part of the fourth ventricle) extend into the spinal canal. This can occur when the skull is too small or misshapen so the brain tissue is pushed downwards into the spinal canal.

The abnormal positioning of the brain can lead to a blockage of signals from the brain to the body or lead to a build-up of cerebrospinal fluid in the brain or spinal cord. It can also put pressure on the brain or the spinal cord and brain stem which may lead to neurological problems. That said, many people with a Chiari malformation have no symptoms so the condition can go unnoticed for a number or years and not need treatment. As imaging tests have become wore widely used, the number of patients that are diagnosed with a Chiari malformation has also gone up, even if they do not present with any symptoms.

Symptoms can vary depending on the severity and type of Chiari malformation that you have. There are three types of Chiari malformation, Chiari I and Chiari II are the most common, however some doctors recognise a Chiari IIII.

Chiari I

  • This is usually asymptomatic, but become apparent in late adolescence

  • Symptoms can include impulse headaches, problems with vision and balance

  • Chiari I malformations occur when part of the skull is too small or deformed, causing the brain to become cramped. This leads to the lower part of the brain (cerebellar tonsils) being pushed into the upper part of the spinal canal.

Chiari II

  • Chiari II is often present at birth and is related to an open myelomeningocele/spina bifida (the backbone and spinal canal do not close properly before birth). This is different to Chiari I, as a larger portion of the brain extends into the spinal canal.

  • This presents with feeding/swallowing, changes in breathing, weakness in the arms and quick downward eye movements

Chari III

  • This is a rare form of Chari, however is very severe. This occurs when a part of the brain protrudes through an opening in the skull called an encephalocele. Chiari III can cause neurological problems and is often diagnosed at birth or in pregnancy.

How is Chiari malformation treated?

The treatment for a Chiari malformation depends on the type and the symptoms.

If the Chiari is asymptomatic then it is likely that there will be no treatment other than regular examinations, follow ups and MRI scans.

If it is symptomatic it will usually be treated with surgery. The purpose of surgery is to stop the progression of symptoms and anatomical changes, while trying to reduce the symptoms that the patient is suffering from.

With a symptomatic Chiari I, it is important that the associated hydrocephalus is treated first (often with a shunt). A posterior fossa decompression may then be done to remove a small amount of bone from the skull, giving the brain more space. In some cases, the surgeon will also remove part of the bone from the spine to give the spinal cord more space. The dura (covering of the brain and spinal cord) can also be thinned to allow the brain and spinal cord to move more freely. All of your surgical options will be discussed before you go ahead with any surgery.

It is important to note that all surgeries come with possible risks and complications, and is important to weigh up and understand the pros and cons of your options before you go ahead with anything.


This article is intended to inform and give insight but not treat, diagnose or replace the advice of a doctor. Always seek medical advice with any questions regarding a medical condition.

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