# 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 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

* 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.