Anencephaly 232035 225505799 2008-07-14T01:27:36Z N2e 1143897 /* Causes */ relation to other diseases: ciliopathies {{Infobox_Disease | Name = Anencephaly | Image Caption = The anterosuperior view of the head of an anencephalic fetus| DiseasesDB = 705 | ICD10 = {{ICD10|Q|00|0|q|00}} | ICD9 = {{ICD9|740.0}} | ICDO = | OMIM = 206500 | MedlinePlus = | eMedicineSubj = neuro | eMedicineTopic = 639 | MeshName = Anencephaly | MeshNumber = C10.500.680.196 | }} '''Anencephaly''' is a [[cephalic disorder]] that results from a [[neural tube defect]] that occurs when the cephalic (head) end of the neural tube fails to close, usually between the 23rd and 26th day of [[pregnancy]]{{Fact|date=May 2008}}, resulting in the absence of a major portion of the brain, skull, and [[scalp]]<ref name="neurologychannel">{{cite web |url=http://www.neurologychannel.com/cephalicdisorders/index.shtml |title=Cephalic disorders - Overview, Anencephaly, Colpocephaly - neurologychannel |accessdate=May 2008}}</ref>. [[Children]] with this disorder are born without a [[forebrain]], the largest part of the brain consisting mainly of the [[telencephalon|cerebral hemispheres]] (which include the [[isocortex]], which is responsible for higher level [[cognition]], i.e., thinking). The remaining brain tissue is often exposed - not covered by bone or skin.<ref name="NINDS"/> ==Presentation== The National Institute of Neurological Disorders and Stroke (NINDS) describes the presentation of this condition as follows: <blockquote>A baby born with anencephaly is usually [[blindness|blind]], [[deafness|deaf]], [[Unconsciousness|unconscious]], and unable to feel [[pain]]. Although some individuals with anencephaly may be born with a rudimentary [[brainstem|brain stem]], the lack of a functioning cerebrum permanently rules out the possibility of ever gaining [[consciousness]]. [[Reflex]] actions such as breathing and responses to sound or touch may occur. <ref name="NINDS">{{cite web |url=http://www.ninds.nih.gov/disorders/anencephaly/anencephaly.htm |title=Anencephaly Information Page: National Institute of Neurological Disorders and Stroke (NINDS) |accessdate = 2008-05-08}}</ref></blockquote> However, the assertion that anencephaly rules out the possibility of consciousness ever being achieved has been specifically disputed.<ref name="pmid17475053">{{cite journal |author=Merker B |title=Consciousness without a cerebral cortex: a challenge for neuroscience and medicine |journal=The Behavioral and brain sciences |volume=30 |issue=1 |pages=63–81; discussion 81–134 |year=2007 |pmid=17475053 |doi=10.1017/S0140525X07000891}}</ref> ==Diagnosis== Anencephaly can often be diagnosed before birth through an [[ultrasound]] examination. The maternal serum [[alpha-fetoprotein]] ([[AFP screening]])<ref name="pmid17602445">{{cite journal |author=Joó JG, Beke A, Papp C, ''et al'' |title=Neural tube defects in the sample of genetic counselling |journal=Prenat. Diagn. |volume=27 |issue=10 |pages=912–21 |year=2007 |pmid=17602445 |doi=10.1002/pd.1801}}</ref> and detailed fetal ultrasound<ref name="pmid16862467">{{cite journal |author=Cedergren M, Selbing A |title=Detection of fetal structural abnormalities by an 11-14-week ultrasound dating scan in an unselected Swedish population |journal=Acta obstetricia et gynecologica Scandinavica |volume=85 |issue=8 |pages=912–5 |year=2006 |pmid=16862467 |doi=10.1080/00016340500448438 |doi_brokendate=2008-06-28}}</ref> can be useful for screening for neural tube defects such as [[spina bifida]] or anencephaly. There are many false diagnoses for anencephaly, as it is not a common diagnosis, often confused with [[exencephaly]] or [[microcephaly]]. Also, sometimes a prognosis stating that an anencephalic baby can live for years is given,often this is the case, but sometimes this cannot occur if the brain is open, because infection sets in rapidly. The anencephalic brain is also usually very disorganised on a cellular level. It depends on the case and individual but often the prognosis is not as grim as it was once reported. There is a support group with much current information under the diagnosis "hydroanencepaly" that is useful in dispelling some of the common myths associated and showing the faces of some of the children affected as they age. ==Prognosis== [[Image:Anencephaly side.jpg|thumb|Side view]] There is no cure or standard treatment for anencephaly and the prognosis for affected individuals is poor. Most anencephalic babies do not survive birth, accounting for 55% of non-aborted cases. If the infant is not [[stillbirth|stillborn]], then he or she will usually die within a few hours or days after birth from cardiorespiratory arrest. In almost all cases anencephalic infants are not aggressively [[resuscitation|resuscitated]] since there is no chance of the infant ever achieving a conscious existence. Instead, the usual clinical practice is to offer [[hydration]], [[food|nutrition]] and [[comfort measures]] and to "let nature take its course". Artificial ventilation, surgery (to fix any co-existing congenital defects), and drug therapy (such as [[antibiotics]]) are usually regarded as futile efforts. Clinicians and medical ethicists may view the provision of nutrition and hydration as medically futile. Occasionally some may even go one step further to argue that [[euthanasia]] is [[morality|morally]] and clinically appropriate in such cases. ==Rate of occurrence== In the [[United States]], approximately 1,000 to 2,000 babies are born with anencephaly each year. Research has suggested that overall, female babies are more likely to be affected by the disorder.<ref name="sexratio">{{cite journal|title=The sex ratio in anencephaly|journal=Genetica|date=1970-02-05|first=J.|last=Timson|coauthors=|volume=41|issue=1|pages=457–465|doi= 10.1007/BF00958926|url=http://www.springerlink.com/content/k5p74661061t5160/|format=|accessdate=2008-05-08 }}</ref> ==Causes== The cause of anencephaly is disputed. Neural tube defects do not follow direct patterns of [[heredity]], though there is some indirect evidence of inheritance<ref name="pmid2333913">{{cite journal |author=Shaffer LG, Marazita ML, Bodurtha J, Newlin A, Nance WE |title=Evidence for a major gene in familial anencephaly |journal=Am. J. Med. Genet. |volume=36 |issue=1 |pages=97–101 |year=1990 |pmid=2333913 |doi=10.1002/ajmg.1320360119}}</ref>, and recent animal models indicating a possible association with deficiencies of the [[transcription factor]] [[TEAD2]].<ref name="pmid17868131">{{cite journal |author=Kaneko KJ, Kohn MJ, Liu C, Depamphilis ML |title=Transcription factor TEAD2 is involved in neural tube closure |journal=Genesis |volume=45 |issue=9 |pages=577–87 |year=2007 |pmid=17868131 |doi=10.1002/dvg.20330}}</ref> Studies show that a woman who has had one child with a neural tube defect such as anencephaly, has about a 3% risk to have another child with a neural tube defect.{{Fact|date=October 2007}} It is known that women taking certain medication for [[epilepsy]] and women with insulin dependent diabetes have a higher chance of having a child with a neural tube defect. [[Genetic counseling]] is usually offered to women at a higher risk of having a child with a neural tube defect to discuss available testing. Recent studies have shown that the addition of [[folic acid]] to the [[diet (nutrition)|diet]] of women of child-bearing age may significantly reduce, although not eliminate, the incidence of neural tube defects. Therefore, it is recommended that all women of child-bearing age consume 0.4&nbsp;mg of folic acid daily,<ref name="NINDS"/> especially those attempting to conceive or who may possibly conceive, as this can reduce the risk to 0.03%.{{Fact|date=May 2008}} It is not advisable to wait until pregnancy has begun, since by the time a woman knows she is pregnant, the critical time for the formation of a neural tube defect has usually already passed. A physician may prescribe even higher dosages of folic acid (4&nbsp;mg/day) for women who have had a previous pregnancy with a neural tube defect. Anencephaly and other physical and mental deformities have also been blamed on a high exposure to such toxins as lead, chromium, mercury, and nickel.<ref>Goldsmith, Alexander (1996, quoted by Millen and Holtz, "Dying for Growth")</ref> === Relation to other rare disorders: genetic ciliopathy === Until recently, the medical literature did not indicate a connection among many [[genetic disorder]]s, both [[Syndrome|genetic syndromes]] and [[Disease|genetic diseases]], that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their [[genotype|root cause]] despite the widely-varying set of medical [[phenotype|symptoms]] that are clinically visible in the [[Disorder (medicine)|disorders]]. Anencephaly is one such disease, part of an [[emergence|emerging]] class of diseases called [[ciliopathy|cilopathies]]. The underlying cause may be a dysfunctional molecular mechanism in the primary [[cilia]] structures of the [[Cell (biology)|cell]], [[organelle]]s which are present in many cellular types throughout the [[human]] body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often [[pleiotropic|multi-symptom]] nature of a large set of syndromes and diseases. Known ciliopathies include [[primary ciliary dyskinesia]], [[Bardet-Biedl syndrome]], [[polycystic kidney disease|polycystic kidney]] and [[polycystic liver disease|liver disease]], [[nephronophthisis]], [[Alstrom syndrome]], [[Meckel-Gruber syndrome]] and some forms of [[retinopathy|retinal degeneration]].<ref>{{cite journal | last = Badano | first = Jose L. | authorlink = | coauthors = Norimasa Mitsuma, Phil L. Beales, Nicholas Katsanis | title = The Ciliopathies : An Emerging Class of Human Genetic Disorders | journal = Annual Review of Genomics and Human Genetics | volume = 7 | issue = | pages = 125-148 | publisher = | location = | date = September 2006 | url = http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.genom.7.080505.115610 | doi = 10.1146/annurev.genom.7.080505.115610 | id = | accessdate = 2008-06-15}}</ref>. ==References== <references/> == External links == * [http://wwwchg.duhs.duke.edu/diseases/anencephaly.html Genetic Basis of Anencephaly] * [http://www.anencephalie-info.org/e/report.htm Anencephalie-info.org] * [http://www.obgyn.net/us/cotm/0006/Exencephaly-Anencephaly.htm Exencephaly – Anencephaly Sequence and its Sonographic Features] * [http://www.gfmer.ch/genetic_diseases_v2/gendis_detail_list.php?cat3=25 Images of Anencephaly] '''(Note: Contains graphic medical images)''' * [http://www.thefetus.net/page.php?id=83 Anencephaly, 3D] * [http://almashriq.hiof.no/ddc/projects/health/specimens/gross-specimens/fetuses/anencephaly/index.html Specimens - Anencephaly] '''(Note: Contains graphic medical images)''' *[http://www.anencephalie-info.org Anencephaly info] {{Congenital malformations and deformations of nervous system}} [[Category:Congenital disorders]] [[de:Anenzephalie]] [[es:Anencefalia]] [[fr:Anencéphalie]] [[it:Anencefalia]] [[he:אננצפלוס]] [[nl:Anencefalie]] [[pl:Bezmózgowie]] [[pt:Anencefalia]] [[fi:Aivottomuus]] [[sv:Anencefali]]