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Handbook of Genetic Counseling/Craniosynostosis-1

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Craniosynostosis

Overview

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  • 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

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  • Primary
    • suture growth is altered
    • head frequently asymmetric
    • 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

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  • 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

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  • 0.4-0.6 per 1000 births
  • so about 1 in 2000 births (Fetology, 2000)

Recurrence risks for isolated nonsyndromic craniosynostosis

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  • 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

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  • 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 improve appearance
  • Surgery for isolated craniosynostosis is usually a single operation and produces excellent cosmetic results in 93%

References

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Notes

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The information in this outline was last updated in 2003.

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