Anatomic Variants on Computed Tomography in Congenital Aural Atresia and Stenosis

OBJECTIVES To quantitatively analyzing the anatomic variants on temporal computed tomography (CT) in congenital external auditory canal stenosis (EACS), congenital aural atresia (CAA), and normal ear structure. METHODS Through a retrospective study, we analyzed 142 temporal high-resolution CT studies performed in 71 microtia patients. The following 6 parameters were compared among the three groups: Marx classification, medial canal diameter, vertical facial nerve (VFN) anterior displacement, tegmen mastoideum position, tympanic cavity volume, and malleus-incus joint or malleus-incus complex (MIC) area. RESULTS The results showed that the microtia distributions in the Marx classification in these three groups were significantly different, as 86% (31 of 35) of ears with major microtia (third-degree dysplasia) had an atresia, and in 54.8% (23 of 42) of the minor microtic (first-degree or second-degree) ears, the bony or cartilaginous part of the external auditory canal was stenotic. Measurement data also showed that the potential medial canal diameter of the atresia group was obviously shorter than that of the stenosis group. The VFN anterior displacement and temporomandibular joint backward-shift together lead to medial canal diameters in ears with atresic canals that is smaller than those with stenotic canals. The tegmen mastoideum position was not significantly different between the three groups. CONCLUSION The mal-development of the external auditory canal is significantly associated with auricle and middle ear developmental anomalies. Compared with CAA ears, EACS have better development of the auricle, canal, tympanic cavity and MIC and relatively safer surgical operation except for the position of the tegmen mastoideum and the VFN.