To investigate the bony segment of the Eustachian tube (ET) using sitting 3D-computed tomography (CT) scans in Patulous Eustachian tube (PET) patients. A retrospective survey of medical records in Sen-En Hospital identified 43 patients and 43 ears with PET and 30 patients and 30 ears with sensorineural hearing loss or vertigo patients as the control. Diagnosis of PET was based on the Proposal on PET Diagnosis Criteria announced by the Otological Society of Japan in 2012. Patients were examined by cone beam CT (Accuitomo; Morita, Kyoto, Japan) in the sitting position. The heights and widths at the tympanic orifice, the middle portion, and isthmus were measured. The lumen of the bony portion was divided into three shapes: peritubal cells (PTC) poor type, PTC good with prominence type, and PTC good without prominence type. In PET patients and the control group, the PTC poor type was identified in nine (21%) and seven ears (23%), PTC good with prominence type was identified in 14 (33%) and seven ears (23%), and PTC good without prominence type was identified in 19 (45%) and 16 ears (53%), respectively. There was no significant difference between the two groups. At the tympanic orifice portion, the average height of the ET lumen was 5.99 ± 1.29 and 6.04 ± 1.41 mm, and the average width of the ET lumen was 2.81 ± 0.82 and 2.78 ± 0.57 mm in the PET and control groups, respectively. The PTC good with prominence type had a significantly smaller width in the tympanic orifice portion than the other types in each group (p < 0.05). The width of the ET lumen in the tympanic orifice averaged 2.87 ± 0.38 and 3.10 ± 0.45 mm in the PTC poor type, 2.23 ± 0.70 and 2.22 ± 0.48 mm in the PTC good with prominence type, and 3.21 ± 0.87 and 2.90 ± 0.50 mm in the PTC good without prominence type in the PET and control groups, respectively. The shape of the bony portion of the ET in PET patients is almost identical to that of controls. Thus, the bony portion has no influence on the pathology of patulous Eustachian tube syndrome. The PTC good with prominence type has a significantly smaller tympanic orifice portion width than the other types. Preoperative evaluation of the bony portion of the ET could provide useful information for ET surgeons.
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