The influence of aging of the hearing system on the variability of the Carhart effect in middle ear diseases.

Abstract

<b>Introduction:</b> In the course of middle ear diseases, a disturbed influence of the system transmitting sound through the middle ear on the function of the inner ear is observed. The audiometric consequence of the disease process taking place in the middle ear is the shift in bone conduction (BC) thresholds, which is called pseudoperceptive hearing loss (the so-called Carhart effect). The natural process of aging of the hearing system (age-related hearing loss) means that the manifestation of the Carhart effect varies in different age groups.<b>Aim:</b> The aim of the study is to assess the influence of the sound transmitting system in the middle ear and the aging of the hearing system on the variability of the Carhart effect in middle ear diseases.<b>Methods:</b> The study included 532 patients with audiometrically confirmed Carhart effect, diagnosed and treated for middle ear diseases in 2010-2020. Three groups of patients were distinguished: otosclerosis, otitis media with effusion treated surgically with myringotomy and subsequent drainage of secretions from the middle ear, chronic otitis media. The behavior of the Carhart effect was assessed by pure tone audiometry performed before and after the therapeutic process.<b>Results:</b> The restoration of physiological amplification of the sound transmitted through the ossicular chain led to a statistically significant change in the Carhart effect and a strong positive correlation between the change in the Carhart effect and the change in average BC thresholds. Canal wall down tympanoplasty coexisting with significant damage to the ossicular chain weakened the influence of middle ear mechanics on the inner ear, being a factor that adversely affected the change in the Carhart effect and the change in average BC threshold values.<b>Conclusions:</b> 1. Restoring the physiological amplification of sound transmitted through the ossicular chain leads to a statistically significant change in the Carhart effect and a change in the average BC threshold values; 2. The role of the impact of aging of the hearing system on the behavior of pseudoperceptive hearing loss is best visible in the case of a properly preserved system transmitting sound through the middle ear; 3. As the damage to the ossicular chain progressed, the type of reconstruction of the ossicular chain played a major role in the audiometrically observed change in the Carhart effect; 4. Canal wall down tympanoplasty coexisting with significant damage to the ossicular chain weakened the influence of middle ear mechanics on the inner ear, being a factor that adversely affected the change in the Carhart effect and the change in average BC threshold values.