National Organization for Rare Disorders, Inc.
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.
Chiari malformations are a group of complex brain abnormalities that affect the area in lower posterior skull where the brain and spinal cord connect. The underlying anatomy of Chiari malformations is thought to be present at birth (congenital), although in many cases they may not become clinically 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. The tonsils may 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, though this is controversial). 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.
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.
American Syringomyelia & Chiari Alliance Project, Inc.
- P.O. Box 1586
- Longview, TX 75606-1586
- Tel: (903)236-7079
- Fax: (903)757-7456
- Tel: (800)272-7282
- Email: email@example.com
- Website: http://www.asap.org
Birth Defect Research for Children, Inc.
- 976 Lake Baldwin Lane
- Orlando, FL 32814
- Tel: (407)895-0802
- Email: firstname.lastname@example.org
- Website: http://www.birthdefects.org
Canadian Syringomyelia Network
- 69 Penny Crescent
- Ontario, L3P 5X7
- Tel: 9054718278
- Fax: 9059444844
- Email: email@example.com
- Website: http://www.csn.ca/
Chiari & Syringomyelia Foundation
- 29 Crest Loop
- Melville, NY 11747
- Tel: (718)966-2593
- Website: http://www.CSFinfo.org
Christopher S. Burton Syringomyelia Foundation, Inc.
- P.O. Box 100335
- Fort Lauderdale, FL 33310-0335
- Tel: (954)727-5137
- Fax: (954)636-2409
- Email: firstname.lastname@example.org
- Website: http://www.thesmfoundation.org
- 320 Osprey Court
- Wexford, PA 15090
- Tel: (724)940-0116
- Fax: (724)940-0172
- Email: email@example.com
- Website: http://www.conquerchiari.org
- 4340 East West Highway Ste 950
- Bethesda, MD 20814
- Tel: (301)202-3811
- Fax: (301)202-3813
- Tel: (888)598-3789
- Email: firstname.lastname@example.org
- Website: http://www.hydroassoc.org
Hydrocephalus Support Group, Inc.
- 1933 Mistflower Glen Ct.
- Chesterfield, MO 63005-4236
- Tel: (636)532-8228
- Fax: (314)251-5871
- Email: email@example.com
March of Dimes Birth Defects Foundation
- 1275 Mamaroneck Avenue
- White Plains, NY 10605
- Tel: (914)997-4488
- Fax: (914)997-4763
- Website: http://www.marchofdimes.com
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
- Website: http://www.ninds.nih.gov/
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: firstname.lastname@example.org
- Website: http://www.sbaa.org
World Arnold Chiari Malformation Association
- 31 Newtown Woods Road
- Newtown Square, PA 19073
- Tel: (610)353-4737
- Email: email@example.com
- Website: http://www.wacma.com
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".
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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.
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Last Updated: 1/4/1970
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