Spina Bifida Family Support

"Families Helping Families"



Provided by the Center for the Study of Inherited and Neurological Disorders (CSIND) Duke University Center

Chiari Malformations

Chiari malformations occur in the region where the brain and spinal cord join. The lower portions of the brain (cerebellar and/or brainstem) are located lower than normal, penetrating out of the skull or protruding into the spinal canal. This misplacement can cause many different symptoms.

Historical note: Chiari malformations were first described in the 1890's by Professor Chiari, a German pathologist. He assigned a grade to the malformations; beginning with Type 1, the mildest form, through Type 4, the most severe. A colleague, Dr. Arnold, added to the type 2 description and hence the name, "Arnold-Chiari malformations". Scientists and physicians use this classification today. Chiari malformations are also known by the following medical terms: herniation of the cerebellar tonsils, cerebellar ectopia, hindbrain herniation, and Arnold-Chiari malformations. Scientists and physicians further define Chiari malformations by the exact millimeter of brain stem that extends into the neck. Chiari type 1 malformations are a result of the smallest degree of herniation and are "NOT" associated with spina bifida. Chiari type 2 malformations occur with an opening of the spine and spinal cord on the lower back. Chiari type 3 and 4 malformations are very rare.

What are the symptoms of a Chiari type 1 malformation?

Symptoms of a Chiari malformation are often vague or nonspecific and as a result many times diagnosis of a Chiari type 1 malformation is delayed. In fact, individuals with Chiari type 1 malformations do not have symptoms. When symptoms are present, headache and neck pain are common complaints. Some individuals with Chiari type 1 malformations report vertigo (dizziness), headaches caused by coughing or laughing, weakness in their arms, a burning like pain in the arms, or severe curvature of the spine. Therefore an individual with a "small Chiari malformation" (which causes less pressure) may have very mild symptoms or no symptoms at all.

The region of the brain affected are the lower brainstem and cerebellum. The lower brainstem controls breathing, swallowing, balance, the vocal cords, eye movements, and sensation and body movements.

What other disorders can occur with Chiari type 1 malformations?

Chiari malformations can occur with other conditions. Some are:

Other associated conditions, include some inherited conditions like achrondroplasia (a type of dwarfism), Hajdu-Cheney syndrome, Albright hereditary osteodystrophy (pseudohypoparanthyroidism), or other rarer syndromes.

Many individuals with Chiari malformations do "NOT" have any other associated medical problems.

How common are Chiari type 1 malformations?

There are no data describing the incidence of Chiari malformations. However, malformations of the cervicomedullary junction, the connection between the brain and spine, are present in approximately 1 percent of live newborns. The most common cervicomedullary junction malformations are Chiari type 1 malformations.

Is one sex more likely than the other have a Chiari type 1 malformation?

No, it does not appear that one sex is more likely to have a Chiari type 1 malformation. However, formal research studies looking at the incidence and prevalence of Chiari type 1 malformations have not been done.

What causes Chiari type 1 malformations?

Scientists do not know the cause of Chiari malformations. Still, there are several hypotheses. One theory suggests that the base of the skull is too small in some individuals and this forced the cerebellar region to be lower than it should be. Another theory suggests that the growth of the cerebellar region is thrown off and overgrowth occurs resulting in the cerebellar region of the brain being compressed lower than it should be. Research studies are ongoing to try to understand how Chiari malformations occur.

Are Chiari type 1 malformations inherited?

There are several families reported in medical literature in which more than one family member has a Chiari malformation. However, no research study has been done to prove or disprove whether Chiari malformations are inherited. CSIND researchers have started a study to determine whether Chiari malformations are inherited (passed from parent to child). IF more than one person in your family has Chiari malformation or a spinal cord problem, please contact CSIND. CSIND's toll free phone number is 800.283.4316. Outside of the United States please call us collect at 919.684.6515.

Available Resources for Families:

American Syringomyelia Alliance Project (ASAP)



Arnold Chiari Family Network



The Canadian Syringomyelia Network



National Organization for Rare Disorders (NORD)



National Institute of Health NIH-NINDS



Center for the Study of Inherited and Neurological Disorders (CSIND)



Syringomyelia Facts


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