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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.


  • Hydroanencephaly

Disorder Subdivisions

  • None

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.


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.


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.

Standard Therapies


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.


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.

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:




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.


March of Dimes Birth Defects Foundation

1275 Mamaroneck Avenue

White Plains, NY 10605

Tel: (914)997-4488

Fax: (914)997-4763

Internet: http://www.marchofdimes.com

The Arc

1825 K Street NW, Suite 1200

Washington, DC 20006

Tel: (202)534-3700

Fax: (202)534-3731

Tel: (800)433-5255

TDD: (817)277-0553

Email: info@thearc.org

Internet: http://www.thearc.org

National Hydrocephalus Foundation

12413 Centralia Rd.

Lakewood, CA 90715-1653


Tel: (562)924-6666

Fax: (562)924-6666

Tel: (888)857-3434

Email: nhf@earthlink.net

Internet: http://www.nhfonline.org

Children's Brain Diseases Foundation

350 Parnassus Avenue

Suite 900

San Francisco, CA 94117


Tel: (415)665-3003

Fax: (415)665-3003

Email: jrider6022@aol.com

Hydrocephalus Association

4340 East West Highway Ste 950

Bethesda, MD 20814


Tel: (301)202-3811

Fax: (301)202-3813

Tel: (888)598-3789

Email: info@hydroassoc.org

Internet: http://www.hydroassoc.org

NIH/National Institute of Neurological Disorders and Stroke

P.O. Box 5801

Bethesda, MD 20824

Tel: (301)496-5751

Fax: (301)402-2186

Tel: (800)352-9424

TDD: (301)468-5981

Internet: http://www.ninds.nih.gov/

Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/

International Hydranencephaly Support Group

11634 203rd Street

Maple Ridge BC, V2X 4T9


Tel: 6044598691

Email: angelbearmom@shaw.ca

Internet: http://www.hydranencephaly.com

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.