The Center for Human Genetics, in collaboration with Dr. Thomas
Milhorat and colleagues, the American Syringomyelia
Alliance Project, and the Canadian Syringomyelia Network is
investigating the hereditary basis of Chiari type I malformations
or without syringomyelia.
What are Chiari malformations?
Chiari malformations occur in the region where the brain and
cord join. The lowerportions of the brain (cerebellar and/or
brainstem) are located lower than normal, penetrating out of the
or protruding into the spinal canal.
Chiari malformations were first described in the 1890's by
Chiari, a German pathologist. He assigned a grade to the
beginning with Type I, the mildest form, classification today.
malformations are also known by the following medical terms:
herniation of the cerebellar tonsils, cerebellar ectopia,
herniation, and Arnold-Chiari malformations, with Arnold-Chiari
malformations being specific to type II malformations. Scientists
physicians further define Chiari malformations by the exact
of brain stem that extends into the neck.
Chiari type I malformations are a result of the smallest degree
herniation and are not associated with spina bifida. Chiari type
malformations are almost exclusively associated with a type of
bifida known as a myelomeningocele, an opening of the spine and
cord on the lower back. Chiari type III and IV malformations are
What other disorders can occur with Chiari
Chiari malformations can occur with other conditions. Some are:
* hydrocephalus (excessive fluid in the brain)
* spina bifida (opening of the spine usually
associated with an
abnormality of the spinal cord)
* syringomyelia (excessive fluid in the spinal cord,
leading to a
cavity detectable by MRI).
* other conditions, including some inherited
achondroplasia (a type of dwarfism),
Albright hereditary osteodystrophy (pseudohypoparathyroidism),
other rarer syndromes.
Many individuals with Chiari malformations do not have any other
associated medical problems.
How common are Chiari malformations?
There are no data describing the incidence of Chiari
However, malformations of the cervico-medullary junction, the
connection between the brain and spine, are present in
percent of live newborns. The most common cervico-medullary
malformations are Chiari malformations.
What are the symptoms of a Chiari malformation?
Some patients with Chiari malformations
are without symptoms. When
symptoms are present, headache and neck
pain are the most common
The affected regions of the brain are the
lower brainstem and
cerebellum. The lower brainstem controls
balance, the vocal cords, eye movements,
and sensation and
movement of the arms and legs. The
cerebellum's most important
function is to coordinate body movements.
Symptoms of a Chiari
malformation are often vague and many
times diagnosis of a Chiari
malformation is delayed.
Some individuals with Chiari
malformations report vertigo
(dizziness), headaches caused by
coughing, weakness in their arms,
a burning-like pain in the arms, severe
curvature of the spine and
The severity of symptoms is often
associated with the degree of
pressure on this portion of the brain.
Therefore an individual
with a "small Chiari
malformation" may have very mild symptoms or
no symptoms at all. Some individuals with
never develop symptoms.
What causes Chiari malformations?
Scientists do not know the cause of Chiari malformations. Still,
are several hypotheses. One theory suggests that the base of the
is too small in some individuals and this forces the cerebellar
lower than it should be. Another theory suggests that the growth
the cerebellar region is thrown off and overgrowth occurs
the cerebellar region of the brain being compressed lower than it
should be. Research studies are ongoing to learn how Chiari
How is syringomyelia associated with Chiari
Syringomyelia (sear-IN-go-my-EEL-ya) is a disorder where abnormal
collection of fluid occurs the spine. This collection of fluid,
composed of cerebral spinal fluid (CSF), is referred to as a
or a "cyst." Syringomyelia can be occur as a res ult of
a car accident
or other trauma. Syringomyelia can also occur with Chiari
malformations or spinal tumors. The symptoms and signs of this
disorder are often vague and may include weakness, fatigue,
or loss of ability to feel hot or cold.
Syringomyelia can be diagnosed with a magnetic resonance imaging
Are Chiari malformations inherited?
There are several families reported in medical literature in
more than one family member has a Chiari malformation. However,
research study has ever been done to prove or disprove whether
malformations are inherited. If more than one person in your
has a Chiari malformation or a spinal cord problem, please
Medical Genetics's toll free telephone number (800) 283-4316.
Participation in the study involves answering questions about
family and medical history, allowing Medical Genetics researchers
review medical records to confirm the diagnosis of Chiari
malformation, and in some instances PROVIDING A BLOOD SAMPLE to
Resources for Families
- American Syringomyelia Alliance Project (ASAP)
National network founded in 1988. Offers
support, networking &
information for individuals with syringomyelia.
P.O. Box 1586
Longview, TX 75606-1586
tel (903) 236-7079
fax (903) 757-7456.
- World Arnold-Chiari Malformation Association (WACMA)
31 Newtown Woods Road,
Philadelphia, PA 19073
- Canadian Syringomyelia Network
69 Penny Crescent Markham,
- National Organization for Rare Disorders (NORD)
P.O. Box 8923
New Farfield, Connecticut 06812-8923
- National Institute of Health NIH-NINDS
Federal Bldg, Room 814
7550 Wisconsin Avenue
Bethesda, MD 20892
Ph: (301) 496-5821
Fax: (301) 402-0302
- Center for Human Genetics
Duke University Medical Center
P.O. Box 2900
Durham, N.C. 27710