| Sci-Tech Dictionary: hydranencephaly |
(medicine) A congenital anomaly in which there are vestiges of a cerebellum, occipital lobes, and basal nuclei; frontal and parietal lobes are replaced by a cyst; and the neurocranium is undeveloped.
Hydranencephaly
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Neurological Disorder:
Hydranencephaly |
Definition
Hydranencephaly is a rare congenital deformity (a deformity that occurs during fetal development) that is characterized by the absence of the cerebral hemispheres of the brain. Instead, the regions of the brain known as the left and right cerebral hemispheres are replaced by sacs that are filled with cerebrospinal fluid.
Description
The absence of the cerebral hemispheres may not be apparent in the first days following birth. The normal and involuntary actions of a newborn such as sucking, swallowing, and crying all occur, as the brainstem controls these actions, and it is usually normal. Moreover, the baby with hydranencephaly appears physically normal, including the size of the head.
The normal behaviors of a growing infant reflect the functions of the left and right cerebral hemispheres. The left hemisphere is normally associated with the acquisition of language. The right hemisphere participates in the perception of space and distance. These sorts of skills are not yet developed in a newborn. Within several weeks to months of birth, the symptoms of hydranencephaly can become apparent.
Demographics
Hydranencephaly is a rare occurrence. It is estimated that one or two babies are born with hydranencephaly worldwide for every 10,000 births. There is no indication that any gender or race is any more susceptible to the disorder.
Causes and symptoms
Within a few weeks of birth, the infant typically becomes irritable and the contraction of the muscles (muscle tone) becomes more pronounced. Muscles may spasm. Seizures can occur. Other symptoms that can develop with time include poor vision or the total loss of vision, poor or no growth, deafness, paralysis, and impaired intellectual development (such as language difficulty).
Hydranencephaly may be caused by a genetic defect, infection associated with vessels, or a trauma that occurs after the twelfth week of pregnancy. Maternal exposure to carbon monoxide early in pregnancy has also been implicated as a possible cause, along with the possibility of early stroke in the developing fetus, or as a result of infection with some viruses.
Diagnosis
Diagnosis is based on the appearance of symptoms noted above. Diagnosis may not be made for weeks or months following birth, because of the initial normal appearance and behavior of the newborn. Prior to birth, ultrasound can reveal hydranencephaly, although techniques for surgical correction in the fetus have not been developed.
Treatment team
A range of medical help, from a family practitioner to pediatric surgeon, can be involved. As well, nurses and family members are part of the care-giving team. Social service workers can refer parents of children with hydranencephaly to community support organizations.
Treatment
There is no definitive treatment for hydranencephaly. Usually, symptoms are treated as they occur and support is provided to make the child as comfortable and happy as possible. Medications are given to control seizures and if excess cerebrospinal fluid collects near the brainstem, a shunt is usually surgically inserted to facilitate redirection of the excess fluid.
Recovery and rehabilitation
Rehabilitation is not stressed for the infant with hydranencephaly, as the long-term prognosis is poor. Physical and occupational therapists may assist in providing treatment to maintain muscle tone for as long as possible, and positioning aids when necessary. Medications are given to control seizures and for comfort.
Clinical trials
As of January, 2004, there were no clinical trials underway or planned in the United States for the study of hydranencephaly. Organizations such as the National Institute for Neurological Disorders and Stroke undertake and fund studies designed to reveal more about the normal development patterns of the brain. By understanding how development can be disrupted, scientists attempt to learn strategies for detecting defects and methods to correct them.
Prognosis
The long-term outlook for children with hydranencephaly is poor. Most children die in their first year of life, although survival past the age of 10 can rarely occur. Currently, the oldest known survivor was 20 years, 6 months old.
Special concerns
Providing support for parents of babies born with hydranencephaly includes genetic counseling and referrals to support groups, where parents can learn practical advice and share information with other parents of children similarly affected. Additionally, mothers who have given birth to a baby with hydranencephaly may be tested for some of the viruses suspected in playing a part in the fetal development of hydranencephaly, including toxoplasmosis, cytomegalovirus, and Herpes simplex virus.
Resources
PERIODICALS
Covington, C., H. Taylor, C. Gill, B. Padaliya, W. Newman, J. R. Smart III, and P. D. Charles. "Prolonged survival in hydranencephaly: a case report." Tennessee Medicine (September 2003): 423–424.
Lam, Y. H., and M. H. Tang. "Serial sonographic features of a fetus with hydranencephaly from 11 weeks to term." Ultrasound Obstetrics and Gynecology (July 2000): 77–79.
OTHER
"NINDS Hydranencephaly Information Page." National Institute for Neurological Diseases and Stroke. (January 20, 2004). www.ninds.nih.gov/health_and_medical/disorders/hydranen_doc.htm.
ORGANIZATIONS
March of Dimes Birth Defects Foundation. 1275 Mamaroneck Avenue, White Plains, NY 10605. (914) 428-7100 or (888) 663-4637; Fax: (914) 428-8203. askus@marchofdimes.com. http://www.marchofdimes.com.
National Information Center for Children and Youth with Disabilities. P.O. Box 1492, Washington, DC 20013-1492. (202) 884-8200 or (800) 695-0285; Fax: (202) 884-8441. nichcy@ead.org. http://www.nichcy.org.
National Institute for Neurological Diseases and Stroke (NINDS). 6001 Executive Boulevard, Bethesda, MD 20892. (301) 496-5751 or (800) 352-9424. http://www.ninds.nih.gov.
National Organization for Rare Disorders. 55 Kenosia Avenue, Danbury, CT 06813-1968. (203) 744-0100 or (800) 999-6673; Fax: (203) 798-2291. orphan@rarediseases.org. http://www.rarediseases.org.
Brian Douglas Hoyle, PhD
| Medical Dictionary: hy·dran·en·ceph·a·ly |
n.
The congenital absence of the cerebral hemispheres in which the space in the cranium that they normally occupy is filled with fluid.
| Veterinary Dictionary: hydranencephaly |
Absence of the cerebral hemispheres, their normal site being occupied by cerebrospinal fluid.
- arthrogryposis and h. — occurs as a combined congenital defect in epidemic form in calves, lambs and kids. It may be caused by intrauterine viral infection with the Akabane and Aino viruses, by poisoning with fungi on lupins, and by inheritance of a conditioning factor. See also akabane virus disease, aino virus disease.
| Wikipedia: Hydranencephaly |
| Hydranencephaly | |
| Classification and external resources | |
| ICD-10 | Q04.3 |
|---|---|
| ICD-9 | 742.3 |
| DiseasesDB | 31516 |
| eMedicine | radio/351 |
| MeSH | D006832 |
Hydranencephaly is a type of cephalic disorder. This is a rare condition in which the cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid.
This should not be confused with hydrocephalus, which is an accumulation of cerebrospinal fluid in the ventricles.
In "hemihydranencephaly", only half of the brain is filled with fluid.[1]
Contents |
Presentation
Usually the cerebellum and brainstem are formed normally, although in some cases the cerebellum may also be absent. An infant with hydranencephaly may appear normal at birth or may have some distortion of the skull and upper facial features due to fluid pressure inside the skull. The infant's head size and spontaneous reflexes such as sucking, swallowing, crying, and moving the arms and legs may all seem normal, depending on the severity of the condition. However, after a few weeks the infant usually becomes irritable and has increased muscle tone (hypertonia). After several months of life, seizures and hydrocephalus may develop. Other symptoms may include visual impairment, lack of growth, deafness, blindness, spastic quadriparesis (paralysis), and intellectual deficits.
Some infants may have additional abnormalities at birth including seizures, myoclonus (involuntary sudden, rapid jerks), and respiratory problems.
Causes
Hydranencephaly is an extreme form of porencephaly, which is characterized by a cyst or cavity in the cerebral hemispheres, and may be caused by vascular insult or injuries, infections, or traumatic disorders after the 12th week of pregnancy.
Diagnosis
Diagnosis may be delayed for several months because the infant's early behavior appears to be relatively normal. Transillumination, an examination in which light is passed through body tissues, usually confirms the diagnosis.
Preliminary diagnosis may be made in utero via standard ultrasound, and can be confirmed with a level II or higher ultrasound.
Prognosis
There is no standard treatment for hydranencephaly. Treatment is symptomatic and supportive. Hydrocephalus may be treated with a shunt.
The prognosis for children with Hydranencephaly is generally quite poor. Death usually occurs in the first year of life.[2]
In a survey completed by 88 families of children with Hydranencephaly from 2006-2007, 69% of the children who had died, did so after their first birthday.[citation needed] The oldest of the children who had died was in their 20s. 62% of the children represented in the survey were over the age of 1 at the time it was filled out. The first year is the hardest for children with Hydranencephaly but survival is possible.
The oldest known survivor was 32, and was observed to have noncortical responses to auditory stimuli.[3]
References
- ^ Ulmer S, Moeller F, Brockmann MA, Kuhtz-Buschbeck JP, Stephani U, Jansen O (2005). "Living a normal life with the nondominant hemisphere: magnetic resonance imaging findings and clinical outcome for a patient with left-hemispheric hydranencephaly". Pediatrics 116 (1): 242–5. doi:. PMID 15995064.
- ^ McAbee GN, Chan A, Erde EL (2000). "Prolonged survival with hydranencephaly: report of two patients and literature review". Pediatr. Neurol. 23 (1): 80–4. doi:. PMID 10963978.
- ^ Counter SA (2007). "Preservation of brainstem neurophysiological function in hydranencephaly". Journal of the Neurological Sciences 263: 198. doi:. PMID 17719607.
External links
- http://www.hydranencephaly.com International Hydranencephaly Support Group]
- Hydranencephaly at NINDS
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