Investigation of the Positional Relationship Between the Tympanic Segment of the Chorda Tympani and the Incus in Patients With Otosclerosis or Middle Ear Anomalies Using Ultra-High Resolution Computed Tomography.

Objective: This study evaluated the sensitivity and accuracy of ultra-high-resolution computed tomography (U-HRCT) in predicting the relationship between the chorda tympani and the long crus of the incus in patients with otosclerosis or middle ear anomalies. Methods: Thirteen patients with otosclerosis or middle ear anomalies were enrolled in this study (three males and ten females; mean age, 41.6 years; range, 7-67 years). The patients underwent U-HRCT (Aquilion Precision; Canon Medical Systems, Japan). Multiplanar reconstruction images were obtained, and the distance between the chorda tympani and the long crus of the incus was measured in a plane parallel to the superstructure of the stapes. In addition, the distance between the two structures was measured during surgery. Subsequently, distances of every 0.5 mm obtained using the two modalities were grouped and compared. Results: The U-HRCT-based evaluation revealed that the mean distance from the chorda tympani to the long crus of the incus was 0.7 mm, whereas the mean actual distance during the surgery was 0.9 mm. In nine of the 13 patients, the U-HRCT-based and actual distances belonged to the same group. In four patients, the U-HRCT measurements were smaller than the actual distances. The chorda tympani was attached to the long crus of the incus in three cases, and U-HRCT precisely predicted this finding in all three cases. Conclusion: U-HRCT is useful for detecting the relationship between the chorda tympani and the long crus of the incus in patients with otosclerosis or middle ear anomalies.