Analysis of the size variability of the human normal and cleft palate fetal nasal capsule by means of three-dimensional computer reconstruction of histologic preparations.

As part of an ongoing study of cleft palate fetal morphology, normal and dysmorphic development of the human fetal nasal capsule was studied in a cross-sectional sample of 29 human fetuses (20 "normal" and 9 cleft), ranging in age from 8 to 21 postmenstrual weeks. The specimens were celloidin embedded, sectioned at 20 microns, and every tenth section stained with hematoxylin and eosin. A computer reconstruction technique was applied to produce three-dimensional representations of the nasal capsule, nasal septal cartilage, and nasal airway. Qualitatively, the cleft palate nasal capsule exhibited gross abnormalities including cartilaginous nasal septum deformities, abnormal septal volume and hypertrophy, reduced nasal airway and capsule volumes, and abnormal spatial relationships between the nasal capsule components. These results suggest that the reduced nasal airways, noted clinically in cleft perinates, may be a function of an interaction of nasal capsule deficiency and nasal septum hypertrophy. However, when lengths and volumes were plotted against fetal postmenstrual age, producing fetal "growth" curves, no significant differences (p greater than 0.05) were noted for growth rates (slopes) or nasal capsule size between the normal and cleft palate fetal samples. Curvilinear regression analysis revealed that both normal and cleft palate nasal capsule and septum lengths changed in a sigmoidal fashion, with the steepest increases from 13 to 17 weeks. In contrast, nasal capsule, airway, and septum volumes changed curvilinearly, showing slow relative growth rates from 8 to 17 weeks, which increased sharply from 18 to 21 weeks. Results suggest that from 8 to 21 weeks prenatally, normal and cleft palate specimens exhibited a similar pattern of fetal nasal capsule development that was characterized by an initial anteroposterior elongation followed by circumferential (i.e., volumetric) growth.