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Chiari Malformations

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Chiari Malformations is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • CM
  • Arnold-Chiari Malformation (ACM)

Disorder Subdivisions

  • Chiari type II (Chiari malformation II)
  • Chiari type III (Chiari malformation III)
  • Chiari type IV (Chiari malformation IV)
  • Chiari type 0 (Chiari malformation 0)
  • Chiari type I (Chiari malformation I)

General Discussion

Summary

Chiari malformations are a group of complex brain abnormalities that affect the area in lower back of the skull where the brain and spinal cord connect. Chiari malformations are thought to be present at birth (congenital), although in many cases they may not become apparent until adulthood. In extremely rare cases, a Chiari malformation may be acquired during life. The exact cause of Chiari malformations are not known, but often the cavity near the base of the skull (posterior fossa) is narrow and abnormally small in relation to the size of the cerebellum, which this portion of the skull encloses. Researchers believe that in some cases the small posterior fossa may cause the developing brain, specifically the cerebellum and the brainstem, to be pushed downward. Part of the cerebellum (known as the cerebellar tonsils) may protrude (herniate) through the foramen magnum, which is the normal opening found in the occipital bone at the base of the skull and the neck. The tonsils thus interfere with the flow of cerebrospinal fluid (CSF) to and from the skull and spinal canal, potentially leading to accumulation of cerebral spinal fluid in the subarachnoid spaces of the brain and spine. A Chiari malformation can also cause pressure on the brain and produce hydrocephalus (pressure due to excessive cerebrospinal fluid accumulation in the brain) and the spinal cord, potentially causing a wide variety of symptoms. In fact, no two cases of Chiari malformation are exactly alike and the associated symptoms are highly variable. The severity of Chiari malformations can vary dramatically as well. In some cases, affected individuals may not develop any symptoms (asymptomatic); in others, severe, potentially debilitating or life-threatening symptoms can develop.



Traditionally, Chiari malformations have been defined and classified by how much of the cerebellar tonsils protrude through the foramen magnum. A diagnosis of a Chiari malformation usually signifies that the cerebellar tonsils protrude below the foramen magnum (often cited as at least 5 millimeters). However, researchers have determined that the length of tonsil descent in a Chiari malformation does not always correspond to the severity of symptoms or to the response to treatment. In fact, some individuals are classified as having Chiari malformation type 0, in which there is minimal or no descent of the cerebellar tonsils. These individuals still have symptoms associated with a Chiari malformation, most likely due to abnormalities in the flow of cerebrospinal fluid within the skull and spinal canal. Research is ongoing to understand the complex, underlying mechanisms that cause Chiari malformations.



Introduction

Chiari malformations are named for Hans Chiari, an Austrian pathologist, who first identified type I-III in 1891. Julius Arnold further expanded the definition of Chiari malformation type II and some medical sources began using the name Arnold-Chiari malformation. Nowadays, some medical sources use Arnold-Chiari malformation as a broad term for all forms. Chiari malformations have also been known as congenital tonsillar herniation, tonsillar ectopia or tonsillar descent.

Resources

American Syringomyelia & Chiari Alliance Project

P.O. Box 1586

Longview, TX 75606-1586

Tel: (903)236-7079

Fax: (903)757-7456

Tel: (800)272-7282

Email: info@asap.org

Internet: http://www.asap.org



March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue

White Plains, NY 10605

Tel: (914)997-4488

Fax: (914)997-4763

Tel: (888)663-4637

Email: Askus@marchofdimes.com

Internet: http://www.marchofdimes.com



Spina Bifida Association of America

4590 MacArthur Boulevard NW

Suite 250

Washington, DC 20007-4226

Tel: (202)944-3285

Fax: (202)944-3295

Tel: (800)621-3141

Email: sbaa@sbaa.org

Internet: http://www.sbaa.org



Hydrocephalus Association

4340 East West Highway Ste 950

Bethesda, MD 20814

USA

Tel: (301)202-3811

Fax: (301)202-3813

Tel: (888)598-3789

Email: info@hydroassoc.org

Internet: http://www.hydroassoc.org



NIH/National Institute of Neurological Disorders and Stroke

P.O. Box 5801

Bethesda, MD 20824

Tel: (301)496-5751

Fax: (301)402-2186

Tel: (800)352-9424

TDD: (301)468-5981

Internet: http://www.ninds.nih.gov/



Canadian Syringomyelia Network

69 Penny Crescent

Markham

Ontario, L3P 5X7

Canada

Tel: 9054718278

Fax: 9059444844

Email: barb@csn.ca

Internet: http://www.csn.ca/



Hydrocephalus Support Group, Inc.

1933 Mistflower Glen Ct.

Chesterfield, MO 63005-4236

USA

Tel: (636)532-8228

Fax: (314)251-5871

Email: hydrob@earthlink.net



Birth Defect Research for Children, Inc.

976 Lake Baldwin Lane

Orlando, FL 32814

USA

Tel: (407)895-0802

Email: staff@birthdefects.org

Internet: http://www.birthdefects.org



World Arnold Chiari Malformation Association

31 Newtown Woods Road

Newtown Square, PA 19073

Tel: (610)353-4737

Email: chiari-owner@yahoogroups.com

Internet: http://www.wacma.com



Christopher S. Burton Syringomyelia Foundation, Inc.

P.O. Box 100335

Fort Lauderdale, FL 33310-0335

Tel: (954)727-5137

Fax: (954)636-2409

Email: info@thesmfoundation.org

Internet: http://www.thesmfoundation.org



Conquer Chiari

320 Osprey Court

Wexford, PA 15090

USA

Tel: (724)940-0116

Fax: (724)940-0172

Email: director@conquerchiari.org

Internet: http://www.conquerchiari.org



Chiari & Syringomyelia Foundation

290 Broadhollow Road, Suite 210E

Melville, NY 11747

Tel: (516)228-3565

Internet: http://www.CSFinfo.org



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, go to www.rarediseases.org and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site www.rarediseases.org or email orphan@rarediseases.org

Last Updated:  6/1/2011

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