Malformations of cranial base structures and pituitary gland in prenatal Meckel syndrome

The sella turcica region, including the clivus and the pituitary gland, was studied histologically in five human fetuses with Meckel syndrome (MS). Al l cases had malformed sella turcica and malformed clivus with irregularly s haped notochordal remnants. We consider that these three characteristics ar e constant phenotypic traits in MS. The adenohypophysis was present in thre e cases. In one of these, ectopia of the gland occurred with adenopituitary tissue overlying the dorsum sella, and in another remnants were found in t he pharyngeal submucosa. In two fetuses the neurohypophysis was not found. The findings in the region were compared to normal findings and to findings in trisomy 18, where cranial base structures radiographically appeared sim ilar to those in MS. We conclude that in MS specific characteristics are fo und in the cranial base region and that radiographic analysis needs to be s upplemented by histological analysis when studying this specific region.