Acalvaria: Difference between revisions
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'''Acalvaria''' is a rare malformation consisting of absence of the [[calvaria (skull)|calvaria]]l bones, [[dura mater]] and associated muscles in the presence of a normal [[human skull|skull]] base and normal facial bones. The [[central nervous system]] is usually unaffected. The presumed pathogenesis of acalvaria is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but an intact layer of skin over the brain parenchyma. |
'''Acalvaria''' is a rare malformation consisting of absence of the [[calvaria (skull)|calvaria]]l bones, [[dura mater]] and associated muscles in the presence of a normal [[human skull|skull]] base and normal facial bones. The [[central nervous system]] is usually unaffected. The presumed pathogenesis of acalvaria is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but an intact layer of skin over the brain parenchyma. In other words, instead of having a skull cap protecting the brain, there is only skin covering it <ref>http://www.rightdiagnosis.com/a/acalvaria/intro.htm</ref>. The size of the area that is missing the skull cap can vary from case to case. In extreme cases, the entire top part of the cranium that is dome-shaped may be absent<ref>http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=945</ref>. |
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== Pathogenesis == |
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Currently there is no identified cause of acalvaria<ref>http://www.rightdiagnosis.com/a/acalvaria/intro.htm</ref>. The primary presumed pathogenesis is problematic migration of the membranous neurocranium with respect to the normal positioning of the immature ectoderm<ref>http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=945</ref>. When an embryo develops normally, the anterior neural pore closes about the fourth week. After this occurs, mesenchymal tissue migrates under the ectoderm. This ectoderm underlies where the cerebral hemisphere will eventually be. When a fetus has acalvaria, the embryonic ectoderm is in its correct place, but the mesenchymal migration does not occur correctly. Therefore, acalvaria is considered to be a postneurulation defect<ref>http://medind.nic.in/ibv/t04/i6/ibvt04i6p618.pdf</ref>. Because it is a postneurulation defect, it must develop after embryonic stage 11, between 24 and 26 days after conception<ref>http://www.jultrasoundmed.org/content/18/11/783.full.pdf</ref>. |
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== References == |
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{{reflist}} |
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== External links == |
== External links == |
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* {{cite journal | author=Harris CP, Townsend JJ, Carey JC | title=Acalvaria: a unique congenital anomaly | journal=Am J Med Genet | year=1993 | pages=694–699 | volume=46 | doi=10.1002/ajmg.1320460620 | issue=6 | pmid = 8362912 }} |
* {{cite journal | author=Harris CP, Townsend JJ, Carey JC | title=Acalvaria: a unique congenital anomaly | journal=Am J Med Genet | year=1993 | pages=694–699 | volume=46 | doi=10.1002/ajmg.1320460620 | issue=6 | pmid = 8362912 }} |
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Revision as of 23:10, 27 November 2012
Acalvaria is a rare malformation consisting of absence of the calvarial bones, dura mater and associated muscles in the presence of a normal skull base and normal facial bones. The central nervous system is usually unaffected. The presumed pathogenesis of acalvaria is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but an intact layer of skin over the brain parenchyma. In other words, instead of having a skull cap protecting the brain, there is only skin covering it [1]. The size of the area that is missing the skull cap can vary from case to case. In extreme cases, the entire top part of the cranium that is dome-shaped may be absent[2].
Pathogenesis
Currently there is no identified cause of acalvaria[3]. The primary presumed pathogenesis is problematic migration of the membranous neurocranium with respect to the normal positioning of the immature ectoderm[4]. When an embryo develops normally, the anterior neural pore closes about the fourth week. After this occurs, mesenchymal tissue migrates under the ectoderm. This ectoderm underlies where the cerebral hemisphere will eventually be. When a fetus has acalvaria, the embryonic ectoderm is in its correct place, but the mesenchymal migration does not occur correctly. Therefore, acalvaria is considered to be a postneurulation defect[5]. Because it is a postneurulation defect, it must develop after embryonic stage 11, between 24 and 26 days after conception[6].
References
- ^ http://www.rightdiagnosis.com/a/acalvaria/intro.htm
- ^ http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=945
- ^ http://www.rightdiagnosis.com/a/acalvaria/intro.htm
- ^ http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=945
- ^ http://medind.nic.in/ibv/t04/i6/ibvt04i6p618.pdf
- ^ http://www.jultrasoundmed.org/content/18/11/783.full.pdf
External links
- Harris CP, Townsend JJ, Carey JC (1993). "Acalvaria: a unique congenital anomaly". Am J Med Genet. 46 (6): 694–699. doi:10.1002/ajmg.1320460620. PMID 8362912.
{{cite journal}}: CS1 maint: multiple names: authors list (link)
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