Geomorphometric Ear Analysis in Individuals with Genetic Syndromes

Abstract Body : Introduction and Objective: Several facial traits are available to capture human facial phenotype. These facial traits may provide valuable information on diagnosing genetic syndromes. In addition, facial characteristics can be easily obtained and can be a non-intrusive diagnostic method. However, little is known about ear structure variation in genetic syndromes. Here, we tested the hypothesis of whether the diagnostic accuracy of morphometric landmarking of ears can be a novel diagnostic tool for four genetic and rare conditions.

Materials and Methods: We recorded the coordinates of 8 ear landmarks and 38 semilandmarks in 2D images from 79 control and 51 pediatric individuals diagnosed with Down (DS), Morquio (MS), Noonan (NS), and Neurofibromatosis type 1 (NF) syndromes to pick up morphological differences in the ear structure associated with each syndrome. Landmark data were superimposed by Generalized Procrustes analysis to remove orientation, location, and scale differences using TPS. We performed a principal component analysis (PCA) and a canonical variates analysis (CVA) to visualize ear shape differences between patients and controls. To assess whether differences were statistically significant, we computed the Procrustes distances (PD) between groups and performed a permutation test using MorphoJ.

Results: A first analysis based on eight ear landmarks only detected significant ear shape differences in individuals with Down syndrome compared to controls (P < 0.0001). When these anatomical landmarks were combined with ear semilandmarks, the analysis captured shape differences in the ear contour. It showed that individuals with Morquio syndrome also showed statistically significant ear shape differences (P = 0.0072). Ear dysmorphology patterns were significantly different in Down and Morquio syndromes (P < 0.0001). However, no significant ear shape differences associated with Noonan (P= 0.3526) and Neurofibromatosis type 1 syndromes (P= 0.1699) were detected in our dataset.

Conclusion and Significance: Geomorphometric ear analysis has the potential to provide a novel diagnostic method in syndromes involving ear dysmorphologies. Implementing landmarking and semilandmarking proves ear morphological variation and significant alterations in DS and MS from unaffected control populations. Future studies assessing ear morphology and positioning might serve as a potential diagnostic or complementary approach for rare and genetic conditions.