[Neurocristopathies of the human nasofrontal bud. Ethmoidal syndromes (hypo- and hyper-septoethmoidism) (author's transl)].

Knowledge of human brain development biology has increased rapidly over the last decade due to fundamental acquisitions in the fields of organogenesis, fetal development, and post-natal growth. The role of the neural crests during cephalic organogenesis, recently studied by Mme Nicole Le Douarin, has given new biological dimensions to the head : it is an organic complex, globally neural in character, and of encephalofacial territorialization. The cervicocephalic region derives this original segmentation from the migratory property of this contingent of the neural crests. In this perspective, the nasofrontal bud is therefore an embryonic cephalic segment, in which appears the pro-encephalon, the eyes, the olfactory bulb, and the median facial zones (bone, cartilage, teeth). Any morphogenetic anomaly in this original craniofacial segment creates associated malformation of the brain, the base of the skull, and the face (eyes and olfactory bulbs) : the neurocristopathies. In this respect, and from the semiological point of view, the face is the "predicate" of the brain. A new classification of these malformations is proposed, based on the clinical study of the ethmoid, a cartilaginous median organ which is accessible clinically. Epigenesis lasts for 18 months in this organ, which forms a part of the face and the neurocranium, and which is known to play a "motor" morphogenetic role on the osteomembranous face : the ethmoidal syndromes (hypo- and hyper-septoethmoidism). Future reports will discuss the neurocristopathies of the branchial arches.