Acalvaria: Difference between revisions
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| specialty = [[Medical genetics]] |
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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. In other words, instead of having a skull cap protecting the brain, there is only skin covering it.<ref name="Right Diagnosis">"Acalvaria." Right Diagnosis. Health Grades Inc., n.d. Web. 27 Nov. 2012. <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 name="Orphanet">"Acalvaria." Orphanet. N.p., n.d. Web. 18 Nov. 2012. <http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN</ref> |
'''Acalvaria''' is a rare malformation consisting of the 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 the faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in the absence of the calvaria, but with 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 name="Right Diagnosis">"Acalvaria." Right Diagnosis. Health Grades Inc., n.d. Web. 27 Nov. 2012. <http://www.rightdiagnosis.com/a/acalvaria/intro.htm {{Webarchive|url=https://web.archive.org/web/20170904183154/http://www.rightdiagnosis.com/a/acalvaria/intro.htm |date=2017-09-04 }}</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 name="Orphanet">"Acalvaria." Orphanet. N.p., n.d. Web. 18 Nov. 2012. <http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN {{Webarchive|url=https://web.archive.org/web/20221011000839/https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN |date=2022-10-11 }}</ref> |
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== |
== Signs and symptoms == |
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There are four main signs of acalvaria: absence of the flat bones of the cranial vault, absence of the dura mater and muscles associated with it, skull abnormalities, and the absence of a skull cap.<ref name="Right Diagnosis"/> This condition can be diagnosed prior to birth using ultrasonography. Physicians often use magnetic resonance imaging to confirm the diagnosis because in utero, acalvaria is sometimes confused with [[anencephaly]] or [[encephalocele]].<ref name="Orphanet"/> A distinguishable difference is that with anencephaly, the cerebral hemispheres are missing, but with acalvaria, all parts of the cerebrum are usually present and developed, whereas parts of the calvarium are missing.<ref name="Harris">Harris, C. P., Townsend, J. J. and Carey, J. C. (1993), Acalvaria: A unique congenital anomaly. Am. J. Med. Genet., 46: 694–699. doi: 10.1002/ajmg.1320460620</ref> |
There are four main signs of acalvaria: absence of the flat bones of the cranial vault, absence of the dura mater and muscles associated with it, skull abnormalities, and the absence of a skull cap.<ref name="Right Diagnosis"/> This condition can be diagnosed prior to birth using ultrasonography. Physicians often use magnetic resonance imaging to confirm the diagnosis because in utero, acalvaria is sometimes confused with [[anencephaly]] or [[encephalocele]].<ref name="Orphanet"/> A distinguishable difference is that with anencephaly, the cerebral hemispheres are missing, but with acalvaria, all parts of the cerebrum are usually present and developed, whereas parts of the calvarium are missing.<ref name="Harris">Harris, C. P., Townsend, J. J. and Carey, J. C. (1993), Acalvaria: A unique congenital anomaly. Am. J. Med. Genet., 46: 694–699. [[doi: 10.1002/ajmg.1320460620]]</ref> |
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== Pathogenesis == |
== Pathogenesis == |
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Currently there is no identified cause of acalvaria.<ref name="Right Diagnosis"/> The primary presumed pathogenesis is problematic migration of the membranous [[neurocranium]] with respect to the normal positioning of the immature [[ectoderm]].<ref name="Orphanet"/> 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 name="Khadilkar">Khadilkar |
Currently there is no identified cause of acalvaria.<ref name="Right Diagnosis"/> The primary presumed pathogenesis is problematic migration of the membranous [[neurocranium]] with respect to the normal positioning of the immature [[ectoderm]].<ref name="Orphanet"/> 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 name="Khadilkar">{{cite journal | last=Khadilkar | first=V. V. | last2=Khadilkar | first2=A. V. | last3=Nimbalkar | first3=A. A. | last4=Kinnare | first4=A. S. | title=Acalvaria | journal=Indian Pediatrics | volume=41 | issue=6 | date=2004 | issn=0019-6061 | pmid=15235172 | pages=618–620|url=https://www.indianpediatrics.net/june2004/june-618-620.htm}}</ref> Because it is a postneurulation defect, it must develop after embryonic stage 11, between 24 and 26 days after conception.<ref name=":0">{{Cite journal|last1=Moore|first1=K.|last2=Kapur|first2=R. P.|last3=Siebert|first3=J. R.|last4=Atkinson|first4=W.|last5=Winter|first5=T.|date=November 1999|title=Acalvaria and hydrocephalus: a case report and discussion of the literature|url=https://pubmed.ncbi.nlm.nih.gov/10547112|journal=Journal of Ultrasound in Medicine|volume=18|issue=11|pages=783–787|doi=10.7863/jum.1999.18.11.783|issn=0278-4297|pmid=10547112|s2cid=38997282|access-date=2024-07-01|archive-date=2022-07-25|archive-url=https://web.archive.org/web/20220725094314/https://pubmed.ncbi.nlm.nih.gov/10547112/|url-status=live}}</ref> |
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[[ACE inhibitor]]s and [[angiotensin II receptor antagonists]] are reported to cause prenatal hypocalvaria.<ref>{{Cite web |url=https://pubmed.ncbi.nlm.nih.gov/30394825/ |title=Prenatal hypocalvaria after prolonged intrauterine exposure to angiotensin II receptor antagonists |access-date=2024-07-01 |archive-date=2024-05-20 |archive-url=https://web.archive.org/web/20240520142826/https://pubmed.ncbi.nlm.nih.gov/30394825/ |url-status=live }}</ref><ref>{{Cite web |url=https://pubmed.ncbi.nlm.nih.gov/1771591/ |title=ACE inhibitor fetopathy and hypocalvaria: the kidney-skull connection |access-date=2024-07-01 |archive-date=2024-05-20 |archive-url=https://web.archive.org/web/20240520142826/https://pubmed.ncbi.nlm.nih.gov/1771591/ |url-status=live }}</ref> |
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== Treatment == |
== Treatment == |
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== Prognosis == |
== Prognosis == |
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Usually babies with this malformation do not survive past birth.<ref name="Orphanet"/> However, there have been cases of survival. As of 2004, there were only two reported living cases. Of these two, one was severely cognitively impaired and physically disabled. The status of the other was unreported. If the fetus progresses to full term |
Usually babies with this malformation do not survive past birth.<ref name="Orphanet"/> However, there have been cases of survival. As of 2004, there were only two reported living cases. Of these two, one was severely cognitively impaired and physically disabled. The status of the other was unreported. If the fetus progresses to full term there is the risk that it will have head trauma from the pressure applied to the head while being delivered.<ref name="Khadilkar"/> A few other cases of acalvaria have been reported that did not progress to birth. In addition to the lack of the skull cap, there were brain malformations in each case and all the pregnancies were terminated either electively or the fetuses were [[Spontaneous abortion|spontaneously aborted]].<ref name=":0" /> |
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== Epidemiology == |
== Epidemiology == |
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Acalvaria usually occurs in less than 1 of every 100,000 births.<ref name="Orphanet"/> By way of epidemiological data, it is thought that females are more prone to have this defect. Currently, acalvaria is not thought to have much of a risk of recurrence.<ref name="Khadilkar"/> |
Acalvaria usually occurs in less than 1 of every 100,000 births.<ref name="Orphanet"/> By way of epidemiological data, it is thought that females are more prone to have this defect. Currently, acalvaria is not thought to have much of a risk of recurrence.<ref name="Khadilkar"/> |
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== See also == |
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* [[Anencephaly]] |
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== References == |
== References == |
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Latest revision as of 00:49, 16 July 2024
| Acalvaria | |
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| Specialty | Medical genetics |
Acalvaria is a rare malformation consisting of the 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 the faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in the absence of the calvaria, but with 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]
Signs and symptoms
[edit]There are four main signs of acalvaria: absence of the flat bones of the cranial vault, absence of the dura mater and muscles associated with it, skull abnormalities, and the absence of a skull cap.[1] This condition can be diagnosed prior to birth using ultrasonography. Physicians often use magnetic resonance imaging to confirm the diagnosis because in utero, acalvaria is sometimes confused with anencephaly or encephalocele.[2] A distinguishable difference is that with anencephaly, the cerebral hemispheres are missing, but with acalvaria, all parts of the cerebrum are usually present and developed, whereas parts of the calvarium are missing.[3]
Pathogenesis
[edit]Currently there is no identified cause of acalvaria.[1] The primary presumed pathogenesis is problematic migration of the membranous neurocranium with respect to the normal positioning of the immature ectoderm.[2] 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.[4] Because it is a postneurulation defect, it must develop after embryonic stage 11, between 24 and 26 days after conception.[5]
ACE inhibitors and angiotensin II receptor antagonists are reported to cause prenatal hypocalvaria.[6][7]
Treatment
[edit]Because this malformation is rare and there are extremely few individuals living with this condition, treatment is limited. Treatment consists of carefully managing the condition in a controlled manner. Proceeding with a bone graft when the child reaches school age is also recommended.[4]
Prognosis
[edit]Usually babies with this malformation do not survive past birth.[2] However, there have been cases of survival. As of 2004, there were only two reported living cases. Of these two, one was severely cognitively impaired and physically disabled. The status of the other was unreported. If the fetus progresses to full term there is the risk that it will have head trauma from the pressure applied to the head while being delivered.[4] A few other cases of acalvaria have been reported that did not progress to birth. In addition to the lack of the skull cap, there were brain malformations in each case and all the pregnancies were terminated either electively or the fetuses were spontaneously aborted.[5]
Epidemiology
[edit]Acalvaria usually occurs in less than 1 of every 100,000 births.[2] By way of epidemiological data, it is thought that females are more prone to have this defect. Currently, acalvaria is not thought to have much of a risk of recurrence.[4]
See also
[edit]References
[edit]- ^ a b c "Acalvaria." Right Diagnosis. Health Grades Inc., n.d. Web. 27 Nov. 2012. <http://www.rightdiagnosis.com/a/acalvaria/intro.htm Archived 2017-09-04 at the Wayback Machine
- ^ a b c d e "Acalvaria." Orphanet. N.p., n.d. Web. 18 Nov. 2012. <http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN Archived 2022-10-11 at the Wayback Machine
- ^ Harris, C. P., Townsend, J. J. and Carey, J. C. (1993), Acalvaria: A unique congenital anomaly. Am. J. Med. Genet., 46: 694–699. doi: 10.1002/ajmg.1320460620
- ^ a b c d Khadilkar, V. V.; Khadilkar, A. V.; Nimbalkar, A. A.; Kinnare, A. S. (2004). "Acalvaria". Indian Pediatrics. 41 (6): 618–620. ISSN 0019-6061. PMID 15235172.
- ^ a b Moore, K.; Kapur, R. P.; Siebert, J. R.; Atkinson, W.; Winter, T. (November 1999). "Acalvaria and hydrocephalus: a case report and discussion of the literature". Journal of Ultrasound in Medicine. 18 (11): 783–787. doi:10.7863/jum.1999.18.11.783. ISSN 0278-4297. PMID 10547112. S2CID 38997282. Archived from the original on 2022-07-25. Retrieved 2024-07-01.
- ^ "Prenatal hypocalvaria after prolonged intrauterine exposure to angiotensin II receptor antagonists". Archived from the original on 2024-05-20. Retrieved 2024-07-01.
- ^ "ACE inhibitor fetopathy and hypocalvaria: the kidney-skull connection". Archived from the original on 2024-05-20. Retrieved 2024-07-01.
External links
[edit]- 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.