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.