Correlation of eustachian tube dimension and chronic otitis media

Background: Eustachian tube (ET) is a dynamically intricate and poorly accessible structure connecting the nose and the middle ear. Although chronic otitis media (COM) is multifactorial disease, ET dysfunction is an important but overlooked predisposing factor. With newer evidence into the dynamics and prognostic factor in outcome of middle ear surgeries, it has become a focus of research. Our study aims to evaluate the various ET parameters using high-resolution computed tomography (HRCT) scan with multiplanar reconstruction technique. These parameters were compared between the diseased and normal ears to evaluate any association between the ET parameters and middle ear disease. Materials and Methods: It is a retrospective study of 66 HRCTs, with 47 HRCTs of COM and rest were controls. ET parameters including (a) ET-angle, (b) length, (c) pretympanic diameter, and (d) diameter at isthmus are measured accurately using HRCT temporal bone. Results: ET angle was significantly obtuse in COM group (154.81° ± 6.33°) when compared with the controls (149.99° ± 6.24°) with P < 0.001. Similar observation in ET angle was noted in diseased ear (154.54° ± 5.79°) in unilateral COM when compared with contralateral ear (149.56° ± 6.87°) (P = 0.001). ET was longer in COM group (3.44 ± 0.31) when compared with controls (3.4 ± 0.35). Pretympanic diameter and diameter at isthmus were greater in control group. Conclusion: The obtuse ET angle and narrow pretympanic diameter may contribute to the pathogenesis of COM. These measurements may be useful in the assessment of ET function preoperatively and might help in determining the surgical outcome. HRCT of temporal bone with multiplanar reconstruction is an effective tool to measure ET dimensions accurately.