Correlation Between Reid–Eustachian Tube Angle, Length, and Diameter Based on Temporal Bone CT Scan with Severity Level in Chronic Suppurative Otitis Media

Abstract

Chronic suppurative otitis media (OMSK) is an inflammatory condition of the middle ear characterized by perforation of the tympanic membrane and persistent otore, with a global prevalence of 65–330 million people, mainly in developing countries such as Indonesia (2.7% in rural areas, 0.7% in urban areas). The Reid–Eustachian tube angle, length, and diameter of the tubes play an important role in the pathogenesis of OMSK as it affects ventilation and drainage of the middle ear. This study explored the correlation of anatomical parameters of the Eustachian tube with the severity of OMSK based on the Middle Ear Risk Index (MERI) Score using CT scan of the temporal bone. Determine the Correlation of Reid–Eustachian Tube angle, length, and diameter of the Eustachian tube based on CT scan with OMSK severity based on MERI Score, and determine optimal threshold values (cut-off) for predicting moderate to severe OMSK severity. Cross-sectional analytical observational research was conducted on 60 OMSK patients at Prof. Dr. I.G.N.G. Ngoerah Hospital, Denpasar, for the period January 2019–December 2024. Reid–tuba angle, length, and diameter data were measured via 128/256-slice CT scan with multiplanar reconstruction. The severity of OMSK was assessed using the MERI Score. Spearman correlation analysis, ordinal logistic regression, and ROC curve were used to evaluate relationships and determine cut-offs. The Reid–Tuba angle showed a significant negative correlation with the MERI score (r = –0.342; p = 0.007). Narrower angles (5–13°) increased the risk of OMSK by 7.823 times more than wider angles (p = 0.011; 95% CI: 1.587–38.542). The ROC curve analysis set a cut-off point of 17.8° to distinguish mild from medium–heavy OMSK, and 15.2° to distinguish moderate OMSK (15.2°–<17.8°) from heavy OMSK (<15.2°). Eustachian tube length (r = –0.040; p = 0.763) and Eustachian tube diameter (r = –0.001; p = 0.994) showed no significant association with OMSK severity. A cut-off of 17.8° provides 100% sensitivity, 96.2% specificity, and a Youden Index of 0.962, with an AUC of 0.991 confirming the classification accuracy is excellent. The Reid–Tuba angle was negatively correlated with the MERI's score, where the narrower angle was associated with a higher severity of OMSK. The analysis showed that the Reid–Tuba angle was able to distinguish light, medium, and heavy OMSK with excellent accuracy, while the length and diameter of the Eustachian tube had no significant effect. These findings confirm the potential of the Reid–Tuba angle as an important anatomical indicator in the early detection and stratification of OMSK severity.