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Genetic and Rare Diseases Information Center (GARD)

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Chiari malformation


* Not a rare disease
Other Names for this Disease
  • Arnold Chiari malformation
  • Arnold-Chiari malformations
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Your Question

My sister has Arnold Chiari malformation (ACM) and I feel like that might be what's going on with me!  Is ACM so rare two sisters couldn't possible have the same conditions?

Our Answer

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

How common are Chiari malformations?

There are no data describing the incidence of Chiari malformations.  However, malformations of the cervico-medullary junctions, the connection between the brain and spine are present in approcimately 1 percent of live newborns.  The most common cervico-medullary junction malformations are Chiari malformations.[1]
Last updated: 6/23/2009

Is it possible for two members of the same family to have a Chiari malfomation?

There are a number of inheritable syndromes (a group of characteristics and/or symptoms that occur together in a recognizable pattern) that are associated with Chiari malformation type 1 such as Klippel-Feil syndrome, hypophosphatemic rickets, renal coloboma syndrome, and many others.[2]  There are also several families that have been reported in the medical literature in which more than one family member has what appears to be an isolated Chiari 1 malformation, not associated with an identified syndrome. Increasing evidence suggests that in some families, there are strong genetic contributors to the development of Chiari malformation type 1.[3]  Researchers continue to search for the gene(s) that are responsible for causing the Chiari malformation.  Magnetic resonance imaging (MRI) scanning is recommended for family members who have signs or symptoms of the disorder.[4]

There is a research study entitled Genetic Analysis of Chiari I Malformation sponsored by the National Institute of Neurological Disorders and Stroke (NINDS) at the US National Institutes of Health that is currently recruiting participants to better understand the genetic factors related to Chiari I malformation and discover the location of the genes responsible for the malformation.  Click on the research study link to learn more about this study.
Last updated: 6/23/2009

  • Duke University Center for Human Genetics. Chiari and Syringomyelia Research. The World Arnold Chiari Malformation Association. Accessed 6/22/2009.
  • Speer M.C, Gorege T.M, Enterline D.S., Franklin A., Wolpert C., Milhorate T.H.. A genetic hypothesis for Chiari 1 Malformation with or without syringomyelia. Neurosurg Focus. 2000;
  • Szewka A.J., Walsh L.. Boaz J., Carvalho K., Golomb M.. Pediatric Neurology. June 2006; Accessed 1/1/1900.
  • Chiari Malformation. American Syringomyelia & Chiari Alliance Project, Inc. . September 2008; Accessed 6/23/2009.