Formation and enlargement of the paranasal sinuses in normal and cleft lip and palate human fetuses.

Abstract

Comparisons of paranasal sinus morphology between humans with and without cleft lip and palate (CLP) have yielded conflicting opinions regarding size differences. Although postnatal samples have been investigated, no studies have compared paranasal sinus volumes between cleft and noncleft human fetuses. The nasal cavities of 20 'normal' and 9 CLP human fetuses (8-21 weeks' postmenstrual age) were examined to assess prenatal volumetric changes of the maxillary sinuses, anterior and posterior ethmoidal air cells, and sphenoidal sinuses. Lengths and volumes of right and left maxillary and sphenoidal sinuses were calculated from histologically prepared sections using a computer reconstruction technique, and regression equations were generated to assess the enlargement rates. All paranasal sinuses were found among both normal and CLP specimens in the same locations and in similar age ranges. However, greater shape asymmetry was noted for all sinuses in CLP compared to normal specimens. In the normal sample, results indicated significant (p < .05) correlations between right or left maxillary sinus length (R2 = 0.49, 0.54) and volume (R2 = 0.67, 0.68), and increasing postmenstrual age, but no significant (p > .05) correlations were observed for right or left sphenoidal sinus length or volumes and postmenstrual age. Maxillary sinus length changes were best described by second-order polynomial regression equations, and volume changes were best described by logarithmic equations. When individual right or left sinuses of CLP specimens were compared to the mean of the normal sample, one maxillary sinus was significantly (p < .05) larger, and 9 maxillary sinuses were not significantly (p > .05) different. Sphenoidal sinus lengths and volumes of CLP specimens were within the same range compared to these dimensions for the normal sample. Results on normal specimens indicate that maxillary sinuses exhibit second-trimester length and volume increases, whereas sphenoidal sinuses are more variable. This study suggests a similar timing of sinus formation in normal and CLP fetuses, but shape asymmetries are frequently detected among CLP specimens. In particular, the sphenoidal sinuses may be altered in shape and size by adjacent, hypertrophic cartilaginous structures in CLP fetuses. These results indicate that the maxillary sinuses of CLP fetuses are not deficient in size compared to noncleft fetuses.