Imaging findings of isolated congenital middle ear malformation on high-resolution computed tomography.

Purpose: This study aims to analyze the imaging features of isolated congenital middle ear malformation (CMEM) on high-resolution computed tomography (HRCT).

Methods: We retrospectively collected patients with surgically confirmed diagnosis of isolated CMEM in our hospital between January 2018 and June 2023. All patients underwent HRCT before surgery. The preoperative imaging findings were analyzed by neuroradiologists with full knowledge of the intraoperative findings.

Results: 37 patients were included in this study, including 25 males and 12 females, with a median age of 16 years. A total of 44 ears underwent surgery. The most commonly affected structures were incudostapedial joint, incus long process, and stapes superstructure, followed by stapes footplate, oval window, incudomalleolar join, tympanic segment of the facial nerve canal, incus body, incus short process and malleus. All incus defect/hypoplasia/malposition, stapes superstructure deformity, malleus deformity, incudostapedial joint discontinuity, and facial nerve canal malposition/abnormal bifurcation could be observed on HRCT. Additionally, 96.0% of stapes superstructure defect, 85.7% of oval window atresia, and 41.7% of incudomalleolar joint fusion, could be visualized on HRCT. HRCT could not show ossicular soft tissue pseudo-connection and stapes footplate fixation.

Conclusions: Preoperative HRCT is an important tool for diagnosing isolated CMEM. The advantages of HRCT lie in its ability to detect ossicular defects/deformities, incudostapedial joint discontinuity, oval window atresia, and facial nerve abnormalities. However, it has a low detection rate for incudomalleolar joint fusion and cannot show ossicular soft tissue pseudo-connection and stapes footplate fixation.