Relationship Between External Ear Severity and Temporal Bone Malformation in Microtia: A Computed Tomography Study

Background/Objectives: Microtia is frequently associated with temporal bone malformations, but the extent to which external ear phenotype reflects underlying CT-defined anatomy remains uncertain. This study aimed to compare the relationships of Marx severity grading and Nagata morphological classification with temporal bone anatomy in patients with microtia. Methods: This retrospective study included 26 patients with 27 affected ears who had both preoperative external ear photographs and temporal bone computed tomography (CT) examinations. Each affected ear was classified according to the Marx and Nagata systems, and temporal bone anatomy was assessed using the modified Jahrsdoerfer CT scoring system. Associations were evaluated using Spearman rank correlation and permutation-based Jonckheere–Terpstra analysis, with an additional patient-level sensitivity analysis. Results: Considerable variation in Jahrsdoerfer scores was observed within external ear phenotypic categories, with substantial overlap between Marx Grades II and III and lower scores concentrated in Grade IV. The inverse association between Marx grade and Jahrsdoerfer score did not reach conventional statistical significance (ρ = −0.380, p = 0.051), whereas the Jonckheere–Terpstra test identified an overall decreasing trend (permutation p = 0.025). This trend no longer reached statistical significance in the patient-level sensitivity analysis. Nagata classification did not significantly discriminate CT-based radiological severity. Conclusions: Greater external auricular severity may be associated with less favorable temporal bone anatomy, but the relationship was not uniform across successive Marx grades. Marx and Nagata classifications provide complementary phenotypic information, but neither consistently reflected the extent of underlying temporal bone malformation. These preliminary findings emphasize phenotype–CT variability and support individualized CT-based anatomical assessment when imaging is clinically indicated.