Introduction: Middle ear volume (MEV) is a clinically relevant parameter across middle ear diseases. MEV values between these techniques have never before been tested for agreement in ears with perforated tympanic membranes (TMs).
Methods: Middle ears were identified from 36 patients ranging 18-89 years of age with TM perforations who underwent tympanometry and temporal bone computed tomography (CT) between 2005 and 2015. MEVs calculated by both tympanometry and three-dimensional volume reconstruction (3DVR) were analyzed for agreement using Bland Altman plots. The differences between tympanometric and 3DVR MEV values for each given middle ear were characterized across MEV quartiles (1 = smallest; 4 = largest) and across increasing states of middle ear disease using Kruskal-Wallis and Wilcoxon testing with Bonferroni correction.
Results: Bland Altman plots demonstrated significant disagreement between MEV measurement techniques. Differences between tympanometric (T) and 3DVR MEV values were significantly greater with increasing average (i.e. (T+3DVR)/2)) MEV per linear regression (p < 0.0001). Significance was demonstrated between fourth and first average MEV quartiles (p = 0.0024), fourth and second quartiles (p = 0.0024), third and first quartiles (p = 0.0048), and third and second quartiles (p = 0.048). Absolute MEV difference was not significantly different across varying states of middle ear disease (p = 0.44).
Conclusion: Statistically and clinically significant disagreement was demonstrated between tympanometric and 3DVR MEV values. Studies that vary in MEV estimation techniques may be expected to demonstrate significantly different results. These preliminary results suggest that clinicians should endeavor to seek further confirmation when interpreting high tympanometric MEV values.
Keywords: Middle ear volume; Three-dimensional volume reconstruction; Tympanic membrane perforation; Tympanometry.