CD-ROM Today 1996 January/CD-ROM Today 1996 January.iso/dp/0357/03579.txt

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$Unique_ID{BRK03579}
$Pretitle{}
$Title{Cerebellar Agenesis}
$Subject{Cerebellar Agenesis Cerebellar Aplasia Cerebellar Hemiagenesis
Cerebellar Hypoplasia Arnold-Chiari Malformation Joubert Syndrome}
$Volume{}
$Log{}

Copyright (C) 1992 National Organization for Rare Disorders, Inc.

919:
Cerebellar Agenesis

** IMPORTANT **
It is possible that the main title of the article (Cerebellar Agenesis)
is not the name you expected.  Please check the SYNONYMS listing to find the
alternate name and disorder subdivisions covered by this article.

Synonyms

     Cerebellar Aplasia
     Cerebellar Hemiagenesis
     Cerebellar Hypoplasia

Information on the following diseases can be found in the Related
Disorders section of this report:

     Arnold-Chiari Malformation
     Joubert Syndrome

General Discussion

** REMINDER **
The Information contained in the Rare Disease Database is provided for
educational purposes only.  It should not be used for diagnostic or treatment
purposes.  If you wish to obtain more information about this disorder, please
contact your personal physician and/or the agencies listed in the "Resources"
section of this report.

Cerebellar Agenesis is a rare disorder thought to be inherited as an
autosomal recessive trait.  Patients with this disorder are born with partial
formation or total absence of the portion of the brain that is located at the
base of the skull known as the cerebellum.  Patients with partial formation
of the cerebellum may have few or no symptoms of the disorder.  When total
absence of the cerebellum is present the patient may experience low muscle
tone, uncontrollable quivering or movements, an inability to coordinate
movement and/or involuntary movement of the eyes.

Symptoms

Patients with Cerebellar Agenesis may have partial or incomplete formation of
the portion of the brain that is located at the base of the skull
(cerebellum).  The cerebellum is the portion of the brain that is concerned
with coordinating voluntary muscle movement such as walking and equilibrium.
When partial formation is present the patient may have few or no symptoms of
the disorder.

When there is a complete absence of the cerebellum, problems such as an
inability to coordinate movement, low muscle tone, uncontrolled quivering
movements with poor balance or a staggering walk, and/or involuntary movement
of the eyes (nystagmus) are more likely to occur.

Some patients with this disorder have also had muscles that do not
stretch properly as well as other abnormalities of the brain that may cause
mental retardation.

Causes

Cerebellar Agenesis is thought to be inherited as an autosomal recessive
trait.  Human traits, including the classic genetic diseases, are the product
of the interaction of two genes, one received from the father and one from
the mother.  In recessive disorders, the condition does not appear unless a
person inherits the same defective gene for the same trait from each parent.
If one receives one normal gene and one gene for the disease, the person will
be a carrier for the disease, but usually will not show symptoms.  The risk
of transmitting the disease to the children of a couple, both of whom are
carriers for a recessive disorder, is twenty-five percent.  Fifty percent of
their children will be carriers, but healthy as described above.  Twenty-five
percent of their children will receive both normal genes, one from each
parent, and will be genetically normal.

Affected Population

Cerebellar Agenesis is a very rare disorder that affects males and females in
equal numbers.  Cases from approximately seven families have been documented
in the medical literature.

Related Disorders

Symptoms of the following disorders can be similar to those of Cerebellar
Agenesis.  Comparisons may be useful for a differential diagnosis:

Arnold-Chiari Syndrome is a rare disorder that is characterized by a
caudal or lower displacement of the brainstem.  Infants with this disorder
may exhibit symptoms such as vomiting, mental impairment, and weakness.
Paralysis of the extremities may also occur.  The presence of Arnold-Chiari
Syndrome in adolescents is generally a milder form.  Dizziness and double
vision may be present.  This malformation is commonly associated with spina
bifida and hydrocephalus.  (For more information on this disorder choose
"Arnold-Chiari" as your search term in the Rare Disease Database).

Joubert Syndrome is a rare disorder in which the patient is born with a
malformation of a portion of the cerebellum called the vermis.  Balance and
coordination may be impaired and there may be psychomotor retardation as well
as uncontrollable eye movement and/or respiratory abnormalities.  Some of the
symptoms may decrease with age.  This disorder is thought to be inherited as
an autosomal recessive trait.  (For more information on this disorder,
choose "Joubert" as your search term in the Rare Disease Database).

Therapies:  Standard

Treatment of Cerebellar Agenesis is symptomatic and supportive.  Special
education services, physical therapy, etc., may be of benefit to children
with Cerebellar Agenesis.

Genetic counseling may be of benefit for patients and their families.

Therapies:  Investigational

Research on birth defects and their causes is ongoing.  The National
Institutes of Health (NIH) is sponsoring the Human Genome Project which is
aimed at mapping every gene in the human body and learning why they sometimes
malfunction.  It is hoped that this new knowledge will lead to prevention and
treatment of genetic disorders in the future.

This disease entry is based upon medical information available through
May 1992.  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.

Resources

For more information on Cerebellar Agenesis, please contact:

     National Organization for Rare Disorders (NORD)
     P.O. Box 8923
     New Fairfield, CT  06812-1783
     [phone]

     Children's Brain Diseases Foundation for Research
     350 Parnassus, Suite 900
     San Francisco, CA  94117
     [phone]
     [phone]

     NIH/National Institute of Neurological Disorders & Stroke (NINDS)
     9000 Rockville Pike
     Bethesda, MD  20892
     [phone]
     [phone]

For Genetic Information and Genetic Counseling Referrals:

     March of Dimes Birth Defects Foundation
     1275 Mamaroneck Avenue
     White Plains, NY 10605
     [phone]

     Alliance of Genetic Support Groups
     35 Wisconsin Circle, Suite 440
     Chevy Chase, MD  20815
     (800) 336-GENE
     [phone]

References

MENDELIAN INHERITANCE IN MAN, 9th Ed.:  Victor A. McKusick, Editor:  Johns
Hopkins University Press, 1990.  Pp. 1082.

BIRTH DEFECTS ENCYCLOPEDIA, Mary Louise Buyse, M.D., Editor-In-Chief;
Blackwell Scientific Publications, 1990.  P. 298.