Alteration in facial shape in the anencephalic human foetus.

Tracings were produced from frontal radiographs of 11 anencephalic foetuses. These were compared analytically with standards derived from 60 normal foetuses. The anencephalics showed a marked reduction in the relative size of the cranium with considerable flattening of the calvarium, which is characteristic of the condition. The orbits were more medially placed, being closer together and somewhat higher in position that the normal foetal outline. The right and left mandible were more elongated with an increase in the intermaxillary space. The condyles were more medially positioned and were closer to the orbits than in the normal outlines. In normal growth, expansion of the brain flattens the cranial base, displacing the nasomaxillary segment forwards. In anencephally this does not happen so that the nasomaxillary segment rotates in an antero-inferior postero-superior direction along with the intermaxillary space and mandible. This produces a significant lengthening of the face accompanied by narrowing in the region of the cranial base relative to the normal outline.