Wormian bones: a review.

Wormian bones are abnormal ossicles that develop from extra ossification centers within the cranium. They are most frequently located in the lambdoid suture or the coronal suture, and have been seen in the fontanelles, particularly the posterior fontanelle. It is unclear at this time exactly how or why they are formed, although genetic as well as environmental factors have been proposed. Their initial formation is thought to be caused by a degree of dural strain and increased sutural width. These conditions can result from mechanically induced stress due to intentional deformation like that practiced in ancient cultures, premature sutural closure, or from reduced skull ossification as seen in metabolic bone diseases. The cause of the malformation can have an influence on the number and location of Wormian bones. Clinically, Wormian bones are used as markers in the diagnoses of many autosomal dominant genetic disorders, namely, craniosynostosis and osteogenesis imperfecta.