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Here is some information I found
About Hydranencephaly
This page is going to be more technical than the other chapters in this book. I want to give you a brief overview of brain development and what happens when there is a problem at different stages of development. There is also information from a radiologist on the diagnosis of Hydranencephaly. And, then is an overview of the brain and brainstem.
Before talking specifically about Hydranencephaly, here is a fairly good overview of brain development and what happens when something goes wrong at a specific stage of development.
Brain Development from Principal Health News http://www.principalhealthnews.c
om/topic/topic100586649
Brain
development begins shortly after conception and continues throughout the growth of a fetus. A complex genetic program coordinates the formation, growth, and migration of billions of neurons, or nerve cells, and their development into discrete, interacting brain regions. Interruption of this program, especially early in development, can cause structural defects in the brain. In addition, normal brain formation requires proper development of the surrounding skull, and skull defects may lead to brain malformation. Congenital brain defects may be caused by inherited genetic defects, spontaneous mutations within the genes of the embryo, or effects on the embryo due to the mother's infection, trauma, or drug use.
Early on in development, a flat strip of tissue along the back of the fetus rolls up to form a tube. This so-called "neural tube" develops into the spinal cord, and at one end, the brain. Closure of the tube is required for subsequent development of the tissue within. Anencephaly (literally "without brain"), results when the topmost portion of the tube fails to close. Anencephaly is the most common severe malformation seen in stillborn births. It is about four times more common in females than males. Anencephaly is sometimes seen to run in families, and for parents who have conceived one anencephalic fetus, the risk of a second is as high as 5%. Fewer than half of babies with anencephaly are born alive, and survival beyond the first month is rare.
Encephalocele is a protrusion of part of the brain through a defect in the skull. The most common site for encephalocele is along the front-to-back midline of the skull, usually at the rear, although frontal encephaloceles are more common among Asians. Pressure within the skull pushes out cranial tissue. The protective layer over the brain, the meninges, grows to cover the protrusion, as does skin in some cases. Defects in skull closure are thought to cause some cases of encephalocele, while defects in neural tube closure may cause others. Encephaloceles may be small and contain little or no brain tissue, or may be quite large and contain a significant fraction of the brain.
Failure of neural-tube closure below the level of the brain prevents full development of the surrounding vertebral bones and leads to spina bifida, or a divided spinal column. Incomplete closure causes protrusion of the spinal cord and meninges, called meningomyelocele. Some cases of spina bifida are accompanied by another defect at the base of the brain, known as the Arnold-Chiari malformation or Chiari II malformation. For reasons that are unclear, part of the cerebellum is displaced downward into the spinal column. Symptoms may be present at birth or delayed until early childhood.
The Dandy-Walker malformation is marked by incomplete formation, or absence of, the central section of the cerebellum, and the growth of cysts within the lowest of the brain's ventricles. The ventricles are fluid-filled cavities within the brain, through which cerebrospinal fluid (CSF) normally circulates. The cysts may block the exit of the fluid, causing hydrocephalus. Symptoms may be present at birth or delayed until early childhood.
Soon after closure of the neural tube, the brain divides into two halves, or hemispheres. Failure of division is termed holoprosencephaly (literally "whole forebrain"). Holoprosencephaly is almost always accompanied by facial and cranial deformities along the midline, including cleft lip, cleft palate, fused eye sockets and a single eye (cyclopia), and deformities of the limbs, heart, gastrointestinal tract, and other internal organs. Most infants are either stillborn or die soon after birth. Survivors suffer from severe neurological impairments.
The normal ridges and valleys of the mature brain are formed after cells from the inside of the developing brain migrate to the outside and multiply. When these cells fail to migrate, the surface remains smooth, a condition called lissencephaly ("smooth brain"). Lissencephaly is often associated with facial abnormalities including a small jaw, a high forehead, a short nose, and low-set ears.
If damaged during growth, especially within the first 20 weeks, brain tissue may stop growing, while tissue around it continues to form. This causes an abnormal cleft or groove to appear on the surface of the brain, called schizencephaly (literally "split brain"). This cleft should not be confused with the normal wrinkled brain surface, nor should the name be mistaken for schizophrenia, a mental disorder. Generalized destruction of tissue or lack of brain development may lead to hydranencephaly, in which cerebrospinal fluid fills much of the space normally occupied by the brain. Hydranencephaly is distinct from hydrocephalus, in which CSF accumulates within a normally-formed brain, putting pressure on it and possibly causing skull expansion.
Excessive brain size is termed megalencephaly (literally "big brain"). Megalencephaly is defined as any brain size above the 98th percentile within the population. Some cases are familial, and may be entirely benign. Others are due to metabolic or neurologic disease. The opposite condition, microcephaly, may be caused by failure of the brain to develop, or by intrauterine infection, drug toxicity, or brain trauma. This information is from Principal Health News http://www.principalhealthn
ews.com/topic/topic10058664
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Radiological Diagnosis of Hydranencephaly
Jim Barkovich, MD is one of the best-known pediatric neuroradiologists in the country. His book, Pediatric Neuroimaging, is one of the most used references on the subject. He defines hydranencephaly as "...a condition in which most of the brain mantle (cortical plate and hemispheric white matter) has been damaged, liquified, and resorbed." This condition may be the end result of more than one causative event. Infection and massive vascular occlusion involving the carotid arteries are the two most often cited. Because hydranencephaly may be a result of different processes the imaging can be somewhat variable. The "classic" appearance is complete replacement of the cerebral hemispheres with fluid. No cortical mantle is visible on MRI. The thalami and cerebellum are usually spared. Some sparing of the inferior frontal and inferior temporal lobes may be present. Roger Harned
The Brain In Hydranencephaly
Basically Hydranencephaly indicates that a child is missing much or most of their cerebral hemispheres, that is, the two masses of folded brain tissue (cortex) that surround the brain stem. Literally "anencephaly" means "without brain", but this is technically incorrect as a term for the cases to which it is applied, which almost invariably have a brain stem. The brain stem is most definitely a part of the brain, and a very important part of the brain.. However, many children have some of their cerebral hemispheres so can use these and learn to do more than would be expected by this diagnosis. Just as all children are different, all children with Hydranencephaly are different as well. What may be a major difficulty for one child (like seizures) may not even be present in another.
What causes Hydranencephaly?
This is a great and often asked question. Unfortunately I don’t believe that there is a clear cause.
Cause Questionnaire # 1 (2001)
58 participants Questionnaire # 2
(2002)
39 participants Questionnaire # 3
(2002-2003)
81 participants
Prenatal Stroke 43.1% 43.59% 38.27%
Prenatal Drug exposure 5.2% 7.69% 11.11%
Prenatal infection 8.6% 5.13% 7.4%
Death of Twin in Utero 6.9% 2.56% 5%
Prematurity 1.7% 0 0
Other 8.6% 10.26% Not asked
Unknown 41.4% 30.77% 44.44%
Obviously there are a variety of causes.
I’m including here some summaries of research projects I’ve found on the Internet.
1. Association of prenatal vascular disruptions with decreased maternal age. (Am J Med Genet 1997 Mar 31;69(3):237-9 Lubinsky MS Department of Pediatrics, Medical College of Wisconsin, Milwaukee, USA.)
Disruptions of fetal structures can create a variety of congenital anomalies. Some apparent prenatal vascular disruptions associate strongly with decreased maternal age, and are rare with older mothers. This is well-documented for gastroschisis, (A birth defect in which there is a separation in the abdominal wall. Through this opening protrudes part of the intestines which are not covered by peritoneum (the membrane that normally lines the inside of the abdomen). Definition from Medicinenet.com) but similar findings with hydranencephaly suggest a general phenomenon that may also involve porencephaly, septo-optic dysplasia, early body stalk disruptions, certain hemifacial anomalies, and other findings. Prenatal vascular disruption may be a common cause of congenital anomalies, but its nature is unknown, and obvious environmental confounders associated with decreased maternal age may have only relatively small contributions. A protective effect for pregnancies of older mothers also remains a possibility.
2. Decreased maternal age with hydranencephaly (Am J Med Genet 1997 Mar 31;69(3):232-4 Lubinsky MS, Adkins W, Kaveggia EG
Department of Pediatrics, Medical College of Wisconsin, Milwaukee, USA.)
We studied parental ages of institutionalized children with hydranencephaly. Mothers under age 20 years and under age 18 years were, respectively, 5 and 10 times as frequent as in the general population, and 3 and 4 times more frequent than for institutionalized control patients. Unwed mothers were also common, but may reflect high rates in younger mothers combined with institutionalization bias. Thus, hydranencephaly appears to show a decreased maternal age effect, similar to that seen with other conditions presumably due to prenatal vascular disruptions. (PMID: 9096748, UI: 97251065 )
Contrary to what is stated in this study our experience has had different results.
Our results were:
Age of Mother at time of birth Questionnaire # 1
2001
58 responses Questionnaire #2
2002
36 replies Questionnaire #3
2002-2003
81 responses
Under 20 44.7% 38.85% 41.94%
Over 20 53.4% 61.1% 56.3%
From the Swiss Society of Neonatology
Hydranencephaly is a rare condition defined as extensive destruction of the brain caused by disruption of brain perfusion. The normal brain tissue is replaced by a membranous sac which is filled with fluid.1 In a series of 4122 autopsies, 363 cases revealed some congenital CNS malformation (235 liveborn infants and 128 stillborn infants), but hydranencephaly was diagnosed in only two patients.2
Disruptions affect mainly the major vessels of the anterior and middle cerebral arteries. Up to the 20th week of gestation neuronal migration is still active. The earlier disruptions occur in the second trimester, the more migrational disorganisation may be found. After 20 weeks of gestation, the brain lesions are not accompanied by cytoarchitectural disorders. During this midgestational period, the neural tube is already closed and well developed. Intact skull and scalp are covering the underlying central nervous system structures and the head appears normal.
Fetal cerebral perfusion can be affected by A) maternal conditions (cardiovascular collapse; trauma; gas poisoning; coagulopathy; cocaine abuse), B) fetal conditions (multiple pregnancy; non-immune hydrops fetalis; blood dyscrasia), or C) placenta and cord pathologies (infarct; calcifications; knot of the cord; neoplasm).3
In surviving infants, neuromotor activity is very limited with some patients developing uncoordinated movements. Convulsions are rarely described because of the absence of a motor cortex in most patients*. The sensory capacities are also very limited with some reaction to strong light. In very rare cases, crying and smiling may be seen.
Prolonged survival of up to 19 years can occur with hydranencephaly; it is, however, not associated with any improvements in consciousness or awareness.4 Electrophysioogic features cannot be used as predictors of the length of survival, whereas some authors have suggested a functioning hypothalamic-pituitary-adrenal axis to be essential for prolonged survival.
* Please note: according to our survey of 81 children with Hydranencephaly 75% of the children have seizures. However they are usually brain stem seizures (see p. for more information)
Antepartum fetal intracranial hemorrhage, predisposing factors and prenatal sonography: a review. Sherer DM, Anyaegbunam A, Onyeije C
(PMID: 9759911, UI: 98430711)
Here’s an interesting article
Hemihydranencephaly: case report and literature review.
Greco F, Finocchiaro M, Pavone P, Trifiletti RR, Parano E.
Department of Pediatrics, University of Catania, Italy.
Hydranencephaly is a severe brain condition characterized by complete or almost complete absence of cerebral cortex with preservation of meninges, basal ganglia, pons, medulla, cerebellum, and falx. It has been ascribed to different causes (infections, irradiations, fetal anoxia, medications, twin-twin transfusion), all leading to vascular disruption. Hemihydranencephaly is an extremely rare condition in which the vascular anomaly is unilateral. We report on a patient who was suspected to have hydrocephalus in utero; a brain magnetic resonance imaging scan showed left-sided hydranencephaly with preservation of basal ganglia. The patient developed signs of right hemiparesis but notably has only mild language delay. The available literature on hemihydranencephaly is reviewed.
http://www.ncbi.nlm.nih.gov/ent
rez/query.fcgi?cmd=Retrieve&db=PubMed&am
p;list_uids=11305691&dopt=Abstract
Caus
e
of Hydranencephaly: print friendly version
I got this form www.hydranecephaly.com

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