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Craniosynostosis
Overview[]
- Craniosynostosis refers to the premature fusion of the cranial sutures (growth centers between the bones of the skull)
- The skull is made up of a number of bones and when those bones fuse together too soon it doesn't allow the head to grow in the usual fashion and can lead to changes in head shape
- Usually cranial sutures do not fuse completely until the fourth decade
Primary vs. secondary craniosynostosis[]
- Primary
- suture growth is altered
- head frequently assymmetric
- the brain continues to grow in areas where sutures are open
- most individuals are normal neurologically
- benefit from surgery
- Secondary
- growth of brain is impaired
- neurologically abnormal usually
Isolated vs. Syndromic[]
- Isolated
- usually presents during first year of life
- usually involves only one cranial suture (may involve more than one though)
- no other associated abnormalities except those produced secondarily as a result of premature fusion of suture
- sagittal suture is most common site for isolated craniosynostosis
- suture that runs from front to back and separates parietal bones
- results in head elongated from front to back due to limited growth laterally (scaphocephaly)
- intracranial pressure is usually in the normal range
- cranial surgery usually recommended to give a more usual head shape
- usually babies with isolated craniosynostosis grow and develop normally
- Syndromic
- Other characteristic features present
- over 60 syndromes described with craniosynostosis as a feature
- bicoronal synostosis is the type present in the most common syndromes
- Most follow AD inheritance
- Most individuals with a craniosynostosis syndrome have normal intelligence
- Saethre-Chotzen syndrome is the most common
- characterized by facial asymmetry, low frontal hairline, ptosis, deviated nasal septum, brachydactyly, and partial cutaneous syndactyly of the toes
- Crouzon - next most common (1 in 25,000 live births)
- characterized by maxillary hypoplasia, shallow orbits, and ocular proptosis
- Apert syndrome
- characterized by strabismus, maxillary hypoplasia
- complete symmetrical syndactyly of hands and feet
- associated with risk for developmental delay (unlike most of the other AD craniosynostosis syndromes)
- Pfeiffer syndrome
- maxillary hypoplasia
- broad thumbs and big toes
- mild cutaneous syndactyly
Incidence of isolated nonsyndromic craniosynostosis[]
- 0.4-0.6 per 1000 births
- so about 1 in 2000 births (Fetology, 2000)
Recurrence risks for isolated nonsyndromic craniosynostosis[]
- usually sporadic
- genetic basis not discovered except for certain cases of unicoronal synostosis
- In study of 125 patients with craniosynostosis only 2.5% of those with isolated synostosis had positive family history
- patients with isolated craniosynostosis and a negative family history are not believed to have an increased incidence of recurrence above the background
Ultrasound detection of craniosynostosis[]
- difficult to detect on ultrasound
- when it is detected it is often not until 3rd trimester
- sometimes features associated with syndrome are detected on ultrasound (fused digits etc)
Surgery
- objective is to allow adequate brain growth and imporve appearance
- Surgery for isolated craniosynostosis is usually a single operation and produces excellent cosmetic results in 93%
References[]
- Bianchi, DW, Crombleholme, TM, and D'alton, ME. Fetology: Diagnosis and management of the fetal patient. McGraw-Hill. 2000.
- http://www.worldcf.org/cran_3a.html - simple definitions of types of craniosynostosis
- http://www.erlanger.org/craniofacial/book/craniosynostosis/cranio_2.htm - great pictures and explanations of the types of craniosynostosis
- http://www.hopkinsmedicine.org/craniofacial/LynmProject/DS/DSSV/SV0.HTM - description and types of craniosynostosis
Notes[]
The information in this outline was last updated in 2003.
Material obtained under GFDL Licence from http://en.wikibooks.org/wiki/Handbook_of_Genetic_Counseling
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