The role of experimental myringosclerosis in interpretation of tympanograms and its possible clinical implications

Abstract

Myringosclerosis (MS) is hyalinization and calcification of the collagen layer in certain areas of the tympanic membrane (TM) and appears as white chalky patches in otomicroscopy. One of the most common sequela from the use of grommets is the development of MS and its rate in the tubed ear ranges between 44% and 54% during long term follow-up. Among tympanometric configurations, type As tympanograms may indicate ossicular fixation, tympanosclerosis or otitis media with effusion. In case of multiple pathologies (e.g., MS and otitis media with effusion), it is not possible to evaluate the effect of a specific pathology in the absence of other, with otomicroscopy and tympanometry. We believe that the movement of TM is hampered by lesions of sclerotic material, thus resulting in decrease of amplitude in tympanograms without any effusion in middle ear. Now, we propose an experimental model specific for creating MS solely on TM and for performing tympanometric measurements on this pure MS model without creating any pathology in the middle ear, to test in what proportion this specific pathology contributes to decrease of amplitude in tympanograms. A myringotomy in rat's TM admits ambient air into the middle ear cavity, resulting in a relatively hyperoxic condition. The result of a myringotomy therefore is an increased production of free oxygen radicals, initiating irreversible tissue damage involving fibrosis, hyalin degeneration and finally apopitosis as observed in MS. After the closure of perforations, tympanometric measurements can be made on this pure MS model. When evaluating a child for suspected otitis media with effusion, the results of the experimental model might have far-reaching clinical implications and might provide suitable target for prevention of unnecessary myringotomies especially in the pediatric age-group.