Frontal Sinus Morphological and Dimensional Variation as Seen on Computed Tomography Scans

SIMPLE SUMMARY: The frontal sinus is an important cavity inside an individual’s forehead and has been used by forensic anthropologists to provide positive identifications due to its highly unique structure from person to person, yet researchers still do not fully understand why it forms as it does. This study examined the differences in both shape and size of the frontal sinuses of over 300 individuals from various ancestral backgrounds and assigned sexes to see if climate adaptations or sexual dimorphism might be driving factors. Results showed that shape was not dependent on where a person descended from nor their assigned sex at birth; however, dimensionally, these variables in combination do cause some significant variation. The results also speak to the idiosyncratic nature of the frontal sinus and bolster confidence in using morphological variations as a means of personal identification. While it is still unknown what causes the significant shape variation between individuals within the U.S., it appears that the frontal sinus is affected more by sexual dimorphism than by the ancestry of the individual. ABSTRACT: Frontal sinus variation has been used in forensic anthropology to aid in positive identification since the 1920s. As imaging technology has evolved, so has the quality and quantity of data that practitioners can collect. This study examined frontal sinus morphological and dimensional variation on computed tomography (CT) scans in 325 individuals for assigned sex females and males from African-, Asian-, European-, and Latin American-derived groups. Full coronal sinus outlines from medically derived CT images were transferred into SHAPE v1.3 for elliptical Fourier analysis (EFA). The dimensional data were measured directly from the images using the MicroDicom viewer. Statistical analyses—Pearson’s chi-square, ANOVA, and Tukey post hoc tests—were run in R Studio. Results indicated that 3.7% lacked a frontal sinus and 12.0% had a unilateral sinus, usually on the left (74.3%). Additionally, no statistically significant morphological clustering using EFA was found based on assigned sex and/or population affinity. However, there were statistically significant differences dimensionally (height and depth) when tested against assigned sex and population affinity, indicating that the interactive effects of sexual dimorphism and adaptive population histories influence the dimensions but not the shape of the frontal sinus.