Skullbase malformations in rat fetuses with hypervitaminosis A‐induced exencephaly

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Abstract
Exencephalic fetuses (16th–20th day), offspring of female Wistar rats treated with vitamin A palmitate orally during pregnancy, were studied in serial sections. The median part of the skullbase of the rat is formed by the basioccipital, basisphenoid, and presphenoid. In exencephalic fetuses the basioccipital had a normal shape; the hypophyseal fossa in the basisphenoid was too deep; the presphenoid was malformed. The angle between the cervical vertebral column and basioccipital was increased and those between the basioccipital and basisphenoid, and the basisphenoid and presphenoid were reduced. As a result the longitudinal axis of the skullbase was shortened. In all exencephalic fetuses the pontine and cervical flexures were less well marked than in controls. No anomalies of the rostral part of the notochord were observed. It is concluded that there is a relation between abnormal flexures of the neural tube and the malformation of the skullbase. The resemblance of the skullbase in human anencephaly and rat exencephaly is emphasized.