Background: The eustachian tube (ET) has a complicated anatomy, which is related to middle ear pathology. The anatomy of the ET has been well investigated in cadavers, but may not accurately reflect that in living subjects. Three-dimensional (3D) computed tomography (CT) was used to examine the ET in patients with patulous ET. Method: The subjects were 35 patients (17 males, aged 59 ± 16 years, and 18 females, aged 44 ± 15 years) with patulous ET which could be continuously traced from the pharyngeal orifice to the tympanic orifice (53 ears). CT was performed in the sitting position at rest, followed by 3D reconstruction. The course of the ET from the middle ear to the pharynx was visualized in 3D surface images. Morphological measurements of the curvature angle (angle C) and the inclination angle (angle I) were determined from 3D coordinates on the CT images. Results: The full length of the ET could be visualized in most patients suffering from patulous ET in the sitting position. Angle C was 21.7 ± 5.8° in the patients aged <40 years (n = 20), which is significantly larger than 16.7 ± 6.8° in the patients aged >59 years (n = 18; Student's t test, p < 0.05). Angle I was 26.5 ± 4.2° in the patients aged <40 years (n = 20), also significantly larger than 21.6 ± 5.8° in the patients aged >59 years (n = 18; Student's t test, p < 0.05). Conclusion: CT in the sitting position is a potential diagnostic tool of the ET and middle ear pathology.
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