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Hydranencephaly

Important
It is possible that the main title of the report Hydranencephaly 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.
Synonyms

* Hydroanencephaly

Disorder Subdivisions

* None

Related Disorders List

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

* Porencephaly
* Hydrocephalus (Hydrocephaly)

General Discussion

Hydranencephaly is a central nervous system disorder characterized by an enlarged head and neurological deficits. The exact cause of Hydranencephaly is not known. This extremely rare form of Hydrocephalus involves the absence of portions of the brain. Results of neurologic examination in newborns may be normal or abnormal. The head usually appears enlarged at birth. Vision impairment, lack of growth and intellectual deficits are symptomatic of this disorder.
Symptoms

Hydranencephaly can usually be detected at birth due to an enlarged head. Some infants may appear healthy at birth but may later fail to grow at a normal rate. Irritability, poor feeding, infantile spasms or seizures, and spasticity or rigidity of arms and legs are symptomatic of this disorder. Some affected individuals may experience an exaggeration of muscular reflexes (hyperreflexia) and/or increased muscle tone (hypertonia). Poor body temperature regulation, vision impairment and mental retardation may also occur.
Causes

Hydranencephaly is suspected to be an inherited disorder although the mode of transmission remains unknown. Some researchers believe that prenatal blockage of the carotid artery where it enters the cranium may be a cause of this disorder. However, the reason for the blockage is not known.

An autosomal recessive inheritance has been described in some cases. 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 occur unless an individual inherits the same defective gene for the same trait from each parent. If an individual 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 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
Affected Populations

Hydranencephaly is a rare disorder that affects males and females in equal numbers.
Related Disorders

Porencephaly is a disorder of the central nervous system involving cerebral cysts or cavities in cortical brain tissue. The disorder can occur before or after birth. Fluid which can accumulate in the head can be drained through a surgical shunt procedure. The prognosis is variable. Some patients with this disorder may develop only minor neurological problems and have normal intelligence, while others may be severely disabled.

Hydrocephalus is a term describing an accumulation of fluid in the brain cavity which usually causes increased pressure inside the skull. It is characterized by enlargement of the head and prominence of the forehead. This disorder may begin suddenly and can be congenital or acquired; it can be a symptom of another disorder or a primary condition. Treatment with a surgical shunt procedure is generally successful in relieving pressure on the brain by draining the fluid out of the head. (For more information on this disorder, choose "hydrocephalus" as your search term in the Rare Disease Database.)

Standard Therapies

Diagnosis
The diagnosis of Hydranencephaly may be confirmed based upon a thorough clinical evaluation, the identification of characteristic physical findings, a detailed patient history, and advanced imaging techniques, such as transillumination, an x-ray of the blood vessels using dye (angiogram), or computerized tomography (CT scan). During CT scanning, a computer and x-rays are used to create a file showing cross-sectional images of internal structures such as the brain.

In some cases, the disorder may be diagnosed before birth (prenatally) using fetal ultrasonography to identify characteristic physical abnormalities. In fetal ultrasonography, an image of the developing fetus is created using sound waves.

Treatment
There is no treatment for Hydranencephaly. A shunt may be recommended to facilitate the drainage of fluid from the brain.
Investigational Therapies

Research into Hydranencephaly and other central nervous system birth defects is ongoing. Understanding the role of genetics in fetal development is a major goal of scientists studying congenital neurological disorders.
References

BIRTH DEFECTS ENCYCLOPEDIA: Mary Louise Buyse, Editor-In-Chief; Blackwell Scientific Publications, 1990. Pp. 885-86.

TEXTBOOK OF CHILD NEUROLOGY, 5th Ed.: John H. Menkes, M.D., Author; Jonathan W. Pine, Jr. et al., Editors; Williams & Wilkins, 1995. Pp. 307-08.

PRINCIPLES OF NEUROLOGY, 6th Ed.: Raymond D. Adams, Maurice Victor, and Allan A. Ropper, Editors; McGraw-Hill, Inc., 1997. P. 995.

NELSON TEXTBOOK OF PEDIATRICS, 15th Ed.: Richard E. Behrman, Editor; W.B. Saunders Company, 1996. P. 1684.

HYDROANENCEPHALY. S. Gabrovski et al.; Ah Vopr Reirokhir (Sept-Oct 1984; 5). Pp. 32-38.

HYDRANENCEPHALY: PRENATAL AND NEONATAL ULTRASONOGRAPHIC APPEARANCE. D. J. Coady et al.; Am J Perinatol (Jul 1985; 2(3)). Pp. 228-30.

ULTRASONOGRAPHIC PRENATAL DIAGNOSIS OF HYDRANENCEPHALY. A CASE REPORT. H. A. Hadi et al.; J Reprod Med (Apr 1986; 31(4)). Pp. 254-56.

DEVELOPMENT OF VISUAL FUNCTION IN HEMIHYDRANENCEPHALY. G. Porro et al.; Dev Med Child Neurol (Aug 1998; 40(8)). Pp. 563-67.

BRAIN FUNCTIONS OF AN INFANT WITH HYDRANENCEPHALY REVEALED BY AUDITORY EVOKED POTENTIALS. T. Yuge et al.; Int J Pediatr Otorhinolaryngol (Sept 15 1998; 45(1)). Pp. 91-95.
Resources

March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: (914)428-7100
Fax: (914)997-4763
Tel: (888)663-4637
TDD: (914)997-4764
Email: Askus@marchofdimes.com
Internet: http://www.marchofdimes.com

The Arc (a national organization on mental retardation)
1010 Wayne Ave
Suite 650
Silver Spring, MD 20910
Tel: (301)565-3842
Fax: (301)565-3843
Tel: (800)433-5255
TDD: (817)277-0553
Email: info@thearc.org
Internet: http://www.thearc.org/

National Hydrocephalus Foundation
12413 Centralia
Lakewood, CA 90715-1623
USA
Tel: 5624023523
Fax: 5629246666
Tel: 8888573434
Email: hydrobrat@earthlink.net
Internet: http://www.nhfonline.org

Children's Brain Diseases Foundation
350 Parnassus Avenue
Suite 900
San Francisco, CA 94117
USA
Tel: 4155665402
Fax: 4158633452
Email: Jr.der6022@aol.com

Guardians of Hydrocephalus Research Foundation
2618 Avenue Z
Brooklyn, NY 11235
Tel: (718)743-4473
Fax: (718)743-1171
Tel: (800)458-8655
Email: GHRF2618@aol.com

Hydrocephalus Association
870 Market Street
Suite 705
San Francisco, CA 94102
USA
Tel: 4157327040
Fax: 4157327044
Tel: 8885983789
Email: info@hydroassoc.org
Internet: http://www.hydroassoc.org

NIH/NINDS Brain Resources and Information Network
PO Box 5801
Bethesda, MD 20824
Tel: (301)496-5751
Fax: (301)402-2186
Tel: (800)352-9424
Internet: http://www.ninds.nih.gov/

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

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.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site www.rarediseases.org or email orphan@rarediseases.org

Last Updated: 8/5/1999
Copyright 1987, 1989, 1999 National Organization for Rare Disorders, Inc.

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