Handbook of Genetic Counseling/Craniosynostosis-1

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 improve 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.