Evaluation and significance of Eustachian tube angles and pretympanic diameter in HRCT temporal bone of patients with chronic otitis media

OBJECTIVE: To evaluate the significance of Eustachian tube (ET) angles and ET pretympanic diameter on high resolution computed tomography (HRCT) Temporal bone in patients with chronic otitis media (COM). METHODS: A retrospective study was carried out at Tertiary care centre. Group A included 92 ears with COM (38 patients with bilateral COM and 16 with unilateral COM); and Group B included 108 normal ears (54 patients with bilateral normal ears). Reid plane-ET angle, Tubotympanic angle and the ET pretympanic diameter was evaluated by HRCT temporal bone, and compared in the two groups. Patients with chronic otitis media (Group A) were subdivided into Group A1 (Blocked ET) and Group A2 (Patent ET). The parameters were evaluated and compared in the subgroups too. RESULTS: The mean Reid plane-ET angle and Tubotympanic angle in Group A was 25.41 ± 2.57 and 148.12 ± 3.43 respectively; whereas in Group B it was 27.56 ± 3.62 and 145.14 ± 4.34 respectively. Reid plane-ET angle was significantly less in patients with COM and Tubotympanic angle was significantly more obtuse in COM patients. ET pretympanic diameter was (5.37 ± 2.10) mm in Group A and (6.47 ± 2.40) mm in Group B. It was significantly less in patients with COM. A significant correlation was found between the ET patency and the two ET parameters (Reid plane-ET angle and pretympanic diameter). CONCLUSIONS: Eustachian tube angles in adults may play a significant role in the etiology of chronic otitis media. Decrease in Reid plane-ET angle and pretympanic diameter on HRCT temporal bone can be used to predict ET dysfunction and to plan the surgical management of chronic otitis media.