MRI validation of the accuracy of tympanometric gradient for the diagnosisof OME

Tympanometry provides a rapid, non-invasive and objective assessment of mid dle ear (ME) status and is widely used for the clinical diagnosis and follo w-up of otitis media with effusion (OME). ME pressure, acoustic admittance and tympanometric gradient are the main test parameters used in making assi gnments to diagnostic classes (i.e. presence or absence of effusion, effusi on quantity). Of these, the tympanometric gradient was suggested to be more sensitive to the presence of effusion, but this has not been demonstrated conclusively and no standard definition of that gradient is accepted. In th is study, 10 cynomolgus monkeys with experimental OME were used to compare the diagnosis of OME made using three different methods to estimate tympano metric gradient with that provided by simultaneous magnetic resonance imagi ng (MRI) of the ME. All three methods of tympanometric gradient measurement were highly correlated with the quantity of ME effusion measured by the MR I. Although not significant, the MRI results were better correlated with th ose for the 'width' method when compared to either the 'difference' or the 'ratio' method of gradient estimation. This study demonstrates the use of M RI as a gold standard for evaluating the accuracy of other methods to diagn ose ME effusion.