MR, CT, and plain film imaging of the developing skull base in fetal specimens

BACKGROUND AND PURPOSE: The developing fetal skull base has previously been studied via dissection and low-resolution CT. Most of the central skull ba se develops from endochondral ossification through an intermediary chondroc ranium, We traced the development of the normal fetal skull base by using p lain radiography, MR imaging, and CT, METHODS: Twenty-nine formalin-fixed fetal specimens ranging from 9 to 24 we eks' gestational age were examined with mammographic plain radiography, CT, and MR imaging. Skull base development and ossification were assessed. RESULTS: The postsphenoid cartilages enclose the pituitary and fuse to form the basisphenoid, from which the sella turcica and the posterior body of t he sphenoid bone originate. The presphenoid cartilages will form the anteri or body of the sphenoid bone. Portions of the presphenoid cartilage give ri se to the mesethmoid cartilage, which forms the central portion of the ante rior skull base, Ossification begins in the occipital bone (12 weeks) and p rogresses anteriorly. The postsphenoid (14 weeks) and then the presphenoid portion (17 weeks) of the sphenoid bone ossify, Ossification is seen latera lly (16 weeks) in the orbitosphenoid, which contributes to the lesser wing of the sphenoid, and the alisphenoid (15 weeks), which forms the greater wi ng, CONCLUSION: MR imaging can show early progressive ossification of the carti laginous skull base and its relation to intracranial structures, The study of fetal developmental anatomy may lead to a better understanding of abnorm alities of the skull base.