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$Unique_ID{BRK03432}
$Pretitle{}
$Title{Agenesis of Corpus Callosum}
$Subject{Agenesis of Corpus Callosum Corpus Callosum Agenesis Asymptomatic
Callosal Agenesis Agenesis of Commissura Magna Cerebri ACC Autosomal recessive
inheritance X-linked dominant inheritance Acquired form Aicardi Syndrome Spina
Bifida Andermann Syndrome}
$Volume{}
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Copyright (C) 1987, 1990 National Organization for Rare Disorders, Inc.

355:
Agenesis of Corpus Callosum

** IMPORTANT **
It is possible the main title of the article (Agenesis of Corpus
Callosum) is not the name you expected.  Please check the SYNONYMS listing to
find the alternate names, disorder subdivisions, and related disorders
covered by this article.

Synonyms

     Corpus Callosum, Agenesis
     Asymptomatic Callosal Agenesis
     Agenesis of Commissura Magna Cerebri
     ACC

DISORDER SUBDIVISIONS:

     Autosomal recessive inheritance
     X-linked dominant inheritance
     Acquired form (caused by infection while still in womb)
     Aicardi Syndrome

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

     Spina Bifida
     Andermann 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.


Agenesis of Corpus Callosum (ACC) is a rare disorder which is present at
birth (congenital).  It is characterized by a partial or complete absence
(agenesis) of an area of the brain that connects the two cerebral
hemispheres.  This part of the brain is normally composed of transverse
fibers.  Agenesis of Corpus Callosum is usually inherited as either an
autosomal recessive trait or an X-linked dominant trait.  It can also be
caused by an infection during the twelfth to the twenty-second week of
pregnancy (intrauterine) leading to developmental disturbance of the fetal
brain.  In some cases mental retardation may result, but in other cases no
evident symptoms may appear and intelligence may not be impaired.

ACC is diagnosed in approximately ninety percent of patients during the
first two years of life.  An epileptic seizure is usually the initial symptom
indicating that a child should be tested for a brain dysfunction.  The
disorder can also be without apparent symptoms in the mildest cases for many
years.  A normal lifespan may be expected for patients with ACC.

Symptoms

The symptoms of Agenesis of Corpus Callosum (ACC) may initially be the onset
of difficult to suppress grand mal or Jacksonian type epileptic seizures
during the first weeks of life, or within the first two years.  (For more
information on these types of seizures choose "epilepsy" as your search term
in the Rare Disease Database).

When the symptoms begin early in life, feeding problems and delays in
holding the head erect are apparent.  Sitting, standing and walking may also
be delayed.  Impairment of mental and physical development, and/or an
accumulation of fluid in the skull (hydrocephalus), are also symptomatic of
the early onset type of this disorder.  (For more information, choose
"hydrocephalus" as your search term in the Rare Disease Database.)

Nonprogressive mental retardation, impaired hand-eye coordination and
visual or auditory (hearing) memory impairment can be diagnosed through
neurological testing of patients with ACC.

In some mild cases, symptoms may not appear for many years.  Older
patients are usually diagnosed during tests for symptoms such as seizures,
monotonous or repetitive speech, or headaches.  Agenesis of Corpus Callosum
can involve a partial or complete absence of the Corpus Callosum, and in mild
cases it may be overlooked due to lack of obvious symptoms during childhood.

Some patients may have deep-set eyes and a prominent forehead.  An abnormally
small head (microcephaly), or sometimes an unusually large head
(macrocephaly), may be present.  Tags of skin in front of the ears
(preauricular skin tags), one or more bent fingers (camptodactyly), delayed
growth, and recurrent bronchopneumonia have also been associated with some
cases of Agenesis of Corpus Callosum.  In other cases wide-set eyes
(telecanthus), a small nose with upturned (anteverted) nostrils, abnormally
shaped ears, excessive neck skin, short hands, diminished muscle tone
(hypotonia), abnormalities of the larynx, heart defects, and symptoms of
Pierre-Robin Syndrome may be present.  (For more information choose
"Pierre-Robin" as your search term in the Rare Disease Database).

Aicardi Syndrome, inherited as an X-linked dominant disorder, consists of
Agenesis of Corpus Callosum, infantile spasms, and abnormal eye structure.
This disorder is an extremely rare congenital disorder in which frequent
seizures, striking abnormalities of the eye's middle coat (choroid) and
retinal layers, and the absence of the structure linking the two cerebral
hemispheres (the Corpus Callosum), accompany severe mental retardation.  Only
females are affected.  (For more information on this disorder, choose
"Aicardi" as your search term in the Rare Disease Database).

Causes

Agenesis of Corpus Callosum is usually inherited as an autosomal recessive
trait or an X-linked dominant trait.  This disorder may also be due in part
to an infection during pregnancy (intrauterine) leading to abnormal
development of the fetal brain.

Human traits including the classic genetic diseases, are the product of
the interaction of two genes for that condition, 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 show no 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.

In X-linked dominant disorders the female with only one X chromosome
affected will develop the disease.  However, the affected male always has a
more severe condition.  Sometimes affected males die before birth so that
only female patients survive.  This seems to be true for one form of Agenesis
of Corpus Callosum known as Aicardi Syndrome.  The majority of patients
diagnosed so far have been females; occasionally Aicardi Syndrome has been
seen in males with an extra X chromosome.

Affected Population

Agenesis of Corpus Callosum produces symptoms during the first two years of
life in approximately ninety percent of those affected.  It is a very rare
condition in the United States.

Related Disorders

Agenesis of Corpus Callosum can occur in conjunction with Spina Bifida.
"Spina Bifida" is a term meaning open (or nonfused) spine.  In Spina Bifida,
one or more of the individual bones of the spine fails to close completely,
leaving a cleft or defect in the spinal canal.  Part of the contents of the
spine can protrude or herniate through this abnormal opening which produces a
meningocele or meningomyelocele.  (For more information on this disorder,
choose "Spina Bifida" as your search term in the Rare Disease Database).

Andermann Syndrome, identified in 1972, is a genetic disorder
characterized by a combination of Agenesis of Corpus Callosum, mental
retardation, and progressive sensorimotor nervous system disturbances
(neuropathy).  All known cases of this disorder originate from Charlevois
County and the Saguenay-Lac St. Jean area of Quebec, Canada.  The exact mode
of inheritance in Andermann Syndrome is unknown at this time.

Therapies:  Standard

Ultrasound and magnetic resonance imaging (MRI) are imaging techniques which
aid in diagnosis of Agenesis of Corpus Callosum.  Treatment is symptomatic
and supportive.  Anti-seizure medications, special education, physical
therapy, and related services may be of benefit depending upon the range and
severity of symptoms.  When hydrocephalus is present it may be treated with a
surgical shunt to drain the fluid from the brain cavity, thereby lowering the
increased pressure on the brain.  Genetic counseling may also be of benefit
to families with this disorder.

Therapies:  Investigational

Research and genetic studies of Agenesis of Corpus Callosum are ongoing.

This disease entry is based upon medical information available through
September 1990.  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 Agenesis of Corpus Callosum, please contact:

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

     Agenesis of Corpus Callosum Network
     86 N. Main St.
     Orono, ME  04473
     [phone]

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

For more information on shunts, please contact:

     Association for Brain Tumor Research
     3725 N. Talmon Ave.
     Chicago, IL  60618
     [phone]

For information on genetics and genetic counseling referrals, please
contact:

     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; Johns Hopkins
University Press, 1990.  Pp. 1111-1112, 1581.

ANATOMICAL AND BEHAVIORAL STUDY OF A CASE OF ASYMPTOMATIC CALLOSAL
AGENESIS:  R. Bruyer, et. al.; Cortex (September 1985, issue 21(3)).  Pp.
417-430.

THE ANDERMANN SYNDROME:  AGENESIS OF THE CORPUS CALLOSUM ASSOCIATED WITH
MENTAL RETARDATION AND PROGRESSIVE SENSORIMOTOR NEURONOPATHY:  A. Larbrisseau,
et.  al.; Can J Neurol Sci (May 1984, issue 11(2)).  Pp. 257-261.

AICARDI'S SYNDROME: (AGENESIS OF THE CORPUS CALLOSUM, INFANTILE SPASMS,
AND OCULAR ANOMALIES):  S. Dinani, et. al.; J Ment Defic Res.  (June 1984,
issue 28 (Pt. 2)).  Pp. 143-149.

ABOUT SHUNTS:  Association for Brain Tumor Research pamphlet.