Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.


Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Chiari malformation type 1


* Not a rare disease
Other Names for this Disease
  • Arnold Chiari malformation type I
  • Chiari malformation type I
  • Chiari type I malformation
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

What causes Chiari malformation type 1? How can I learn about research on this topic? In particular I'm interested in learning more about the role of genetics and possible links to radiation or drug exposure.

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is Chiari malformation type 1?

Chiari malformation type 1 is a structural abnormality of the cerebellum, the part of the brain that controls balance. It involves the extension of the lower part of the cerebellum into the foramen magnum (the large hole at the base of the skull which allows passage of the spinal cord), without involving the brainstem. Normally, only the spinal cord passes through this opening. This malformation is the most common type of Chiari malformation and may not cause any symptoms.[1] Depending on the symptoms present and severity, some individuals may not require treatment while others may require pain medications or surgery.[2][3]
Last updated: 3/12/2012

What causes Chiari malformation type 1?

Primary or congenital Chiari malformations are caused by structural defects in the brain and spinal cord that occur during fetal development. The underlying cause of the structural defects are not completely understood, but may involve genetic mutations or lack of proper vitamins or nutrients in the maternal diet.[1]

Less frequently, Chiari malformation type 1 is acquired after birth. Causes of acquired Chiari malformation type 1 involve the excessive draining of spinal fluid from the lumbar or thoracic areas of the spine as a result of injury, exposure to harmful substances, or infection.[1] Click here to view a diagram of the spine.

Last updated: 3/12/2012

Is Chiari malformation type 1 genetic?

Genes are thought to play a role in the development of Chiari malformation type 1, however at this time the genetics of this malformation is not completely understood.  There is a clinical trial titled, Genetic Analysis of the Chiari I Malformation, which may be of interest to you. Click on the study title to learn more.  

You can search for additional studies at The U.S. National Institutes of Health, through the National Library of Medicine, developed to provide patients, family members, and members of the public with current information on clinical research studies. To search for trials, click on the link above and use 'Chiari malformation' as your search term. After you click on a study, review its 'eligibility' criteria to determine its appropriateness. Use the study’s contact information to learn more. Check this site often for regular updates.
Last updated: 2/10/2010

Can Chiari malformation type 1 be caused by drug or radiation exposure?

Acquired Chiari malformation type 1 may be due to injury, exposure to harmful substances, or infection that results in the excessive draining of spinal fluid from the lumbar or thoracic areas of the spine.[1]
Last updated: 2/10/2010