Ontogenetic patterns in human frontal sinus shape: A longitudinal study using elliptical Fourier analysis

Abstract

Frontal sinus morphology is highly variable across individuals, but little is known regarding how or at what age that variation is reached. Existing ontogenetic studies are conflicting and often cross-sectional in nature, limiting understanding of individualistic growth. Studies investigating sinus growth with longitudinal series often focus on lateral cephalograms and consequently do not capture the sinus morphological features that are most relevant to clinical and medicolegal settings (e.g., arcade/scalloping, width-to-height dimensions, asymmetry). Longitudinal analysis of sinus morphology from frontal radiographs is important to understand when sinus morphology stabilizes. The purpose of this study was to investigate at what age the frontal sinus attains its final shape, and whether sex-based differences in ontogeny are evident, using a longitudinal sample of posterior-anterior (PA) frontal radiographs from the AAOF Legacy Collection. Frontal sinus outlines were manually traced in 935 radiographs from 111 individuals (55F/56M) spanning 8-29 years of age. Outlines were subjected to elliptical Fourier analysis (EFA) and underwent principal components analysis (PCA). PC1 (51.02% of variation) appears to represent the relative height and breadth of the sinus, PC2 (11.73%) and PC3 (10.03%) captures the degree of relative complexity in the outlines. Individual PC scores were plotted against age-inmonths with individual Loess growth curves. Overall, younger individuals typically display relatively shorter, flatter sinuses, increasing in vertical complexity with age.Mixed-effect models on PC1 indicate significant effects for the repeated measure of years (p < 0.001). Within individuals, Euclidean distances of PCs between each sinus outline and their oldest-age outline (i.e., final morphology) were calculated and plotted against age-in-months with Loess growth curves. The results indicate that final frontal sinus morphology is mostly attained by 20 yoa regardless of sex. There is sexual dimorphism in ontogenetic trajectories: females attain frontal sinus shape earlier than males. Specifically, Loess growth curves of the Euclidean distances to final sinus shape indicate that female shape shows decreased development at 14-16 yoa, with males approaching stabilization at 18-20 yoa. These trends were supported by paired t-tests on PC1 between each year and the oldest age, whereby significant differences end for females starting at 15 and 18 yoa for males. The timing of shapestabilization in the current study closely aligns with previous studies on linear and size dimensions, indicating a close relationship between the ontogeny of frontal sinus shape and size. This research has several implications in diverse fields. Documenting

Technical Modifications for the Application of the Total Difference Method for Frontal Sinus Comparison

“…Although ancestry is not listed, the samples are likely largely composed of European-American individuals. Radiographs and frontal sinus outlines (see details below) were previously collected for larger, ongoing studies of frontal sinus morphology and identification methods, e.g., [ 25 , 26 ]. The sample included ten outlines which were randomly selected in R from 244 possible sinus outlines on 128 adult individuals used in a previous study (note: some individuals had several radiographs at different age points, explaining the higher number of outlines versus individuals) [ 27 ].…”

“…As a recent study noted that the frontal sinus shape stabilizes at around 15 years of age in females and 18 years of age in males [ 26 ], the inclusion criteria included an age of 18 years or older (adult) and no obvious pathological conditions. Sex was not considered in obtaining the random sample, as the original study did not find sex-based significant differences [ 16 ].…”

Variation, sexual dimorphism, and enlargement of the frontal sinus with age in adult South Africans

“…Both Brown et al (1984) and Gagliardi et al (2004) measured lateral flat plane cephalograms, and the ontogenetic series examined did not extend beyond the end of ossific fusion of the wrist (Gagliardi et al, 2004) or 24 years of age (Brown et al, 1984). As such, as noted by Butaric, Campbell, et al (2022), the actual specific growth patterns exhibited by individuals remain poorly known. Only the longitudinal study of Brown et al (1984) examined the development of the frontal sinus beyond the end of adolescent growth.…”

Age-Related Changes to Frontal Sinus Traits and Implications for Forensic Identification

“…The age at which the frontal sinus reaches its adult size and shape is also still largely unknown. Generally, terminal development of the frontal sinuses has been suggested to occur by 18-20yoa (Brown et al 1984;Butaric et al 2022a;Fatu et al 2006;Schuller 1921;Marek et al 1983;Prossinger 2001;Rennie et al 2017;Sardi et al 2018;Spaeth et al 1997;Yun et al 2011). Studies on sinus size (e.g., sinus volume, area, or linear dimensions) indicate that while the sinuses tend to appear earlier in males (Brown et al 1984;Gagliardi et al 2004), females tend to reach their adult state earlier (Brown et al 1984;Gagliardi et al 2004;Prossinger 2001;Sardi et al 2018).…”

“…Around this time, the frontal sinus usually expands superiorly above the orbital borders and is more easily distinguished from the ethmoidal air cells, which tend to obscure smaller frontal sinuses in radiographs. The linear dimensions, overall shape, and complexity of the frontal sinus continues to increase with age into early adulthood, with most sinus growth occurring during puberty (Brown et al1984;Butaric et al 2022a;Fatu et al 2006;Gagliardi et al 2004;Quatrehomme et al 1996;Sardi et al 2018).…”