Objective: To evaluate the application of 10 μm otology CT on evaluation of isolated malleus fixation (IMF) in patients with conductive hearing loss. Methods: A total of 19 patients (25 sides) with idiopathic hearing loss, including 8 males and 11 females, aged between 4 to 50 years, who underwent 10 μm otology CT examination in Department of Radiology, Beijing Friendship Hospital, Capital Medical University from October 2020 to July 2021, were retrospectively collected. For those patients with idiopathic hearing loss, there were 5 cases (6 sides), including 2 males and 3 females, with an average age of 18-70 [65(20,68)] years, with bony connection between malleus and tympanum wall. Eighteen sex-and age-matched cases with normal hearing group, including 6 males and 12 females, with an average age of 20-68 (39±14) years, as the ratio of 1∶3, were included as the controls. The distances of the tegmen tympani between malleus head and horizontal semicircular canal, as well the distances between malleus head and horizontal semicircular canal were retrospectively measured and further compared between the two groups. Results: The incidence of IMF in patients with idiopathic conductive hearing loss without other etiologies was 24.0% (6/25). The specificity of 10 μm otology CT in diagnosing IMF was 100%. The distances of tegmen tympani between horizontal semicircular canal and malleus head in IMF patients were significantly smaller compared with the controls [-0.65(-1.21, -0.35) mm vs 1.34(0.04, 1.68) mm;0.92(0.51, 1.49) mm vs 2.82(1.76, 3.53) mm](both P<0.05, respectively). There was no significant difference in distances between malleus head and horizontal semicircular canal [-1.30 (-1.90, -0.46)mm vs -0.42 (-1.15, 0.05),P=0.057]. Conclusions: IMF is not uncommon in conductive hearing loss without other causes, which can be clearly shown by 10 μm otology CT. Its occurrence is related to the local downward shift of tegmen tympani above the malleus, without upwards displacement of the malleus.
目的： 探讨10 μm级耳科专用CT在评估传导性耳聋患者单纯锤骨固定（IMF）发生情况中的应用。 方法： 回顾性收集2020年10月至2021年7月首都医科大学附属北京友谊医院放射科行10 μm级耳科专用CT检查的患者资料，最终共纳入“特发性”传导性耳聋患者19例（25侧），男8例，女11例，年龄4~50（37±20）岁，其中IMF者5例（6侧），男2例，女3例，年龄18~70［65（20，68）］岁。按1∶3纳入性别年龄匹配的听力正常者18例（18侧）作为IMF的对照组，男6例，女12例，年龄20~68（39±14）岁。测量鼓室盖与锤骨头间距、鼓室盖与水平半规管间距及锤骨头与水平半规管间距。分析比较两组间鼓室盖与锤骨头间距、鼓室盖与水平半规管间距及锤骨头与水平半规管间距。 结果： 在无其他病因的“特发性”传导性耳聋患者中IMF的发生率为24.0%（6/25）。10 μm级耳科专用CT诊断IMF特异度为100%。IMF患者的鼓室盖-水平半规管间距、鼓室盖-锤骨头间距较对照组显著减小［-0.65（-1.21，-0.35）mm比1.34（0.04，1.68）mm；0.92（0.51，1.49）mm比2.82（1.76，3.53）mm］（均P<0.05）；锤骨头-水平半规管间距两组间差异无统计学意义［-1.30（-1.90，-0.46）mm比-0.42（-1.15，0.05），P=0.057］。 结论： IMF在无其他病因的传导性耳聋中并不少见，10 μm级耳科专用CT可清晰显示此征象；其发生与锤骨上方鼓室盖局限性低位有关，不伴锤骨上移。.