Changes in middle ear transmission characteristics secondary to altered bone remodelling

Alteration in the process of bone remodelling results in conditions like osteopenia and osteoporosis in which the bones become susceptible to fracture. The functioning of middle ear bones in such individuals were assessed in this study and it was found that the middle ear bones are equally susceptible to micro-fractures and can cause reduction in the transmission of sound energy.

Alteration in the process of bone remodelling or increase in the number of osteoclasts cells as it occurs in osteoporosis and osteopenia are likely to affect the middle ear bones in the same way it affects the skeletal bones. Whether these micro-structural changes occurring at the level of the middle ear secondary to altered bone remodelling cause any significant impairment in its functioning is not explored. Thus, the present study aimed at assessing the different aspects of middle ear functioning in individuals with reduced BMD.

The study included 25 normal, 39 osteopenic and 40 osteoporotic participants. The participants underwent pure-tone audiometry, otoscopic examination, conventional immittance evaluation using a 226 Hz probe tone, multi-component and multi-frequency tympanometry and acoustic reflex threshold testing. None of the participants had any current or previous history of middle ear effusion.

A significantly higher proportion of participants in the clinical group had hearing loss compared to the normal group. The clinical group participants also had reduced middle ear resonance frequency, elevated static compliance values and elevated or absent acoustic reflexes compared to the normal participants. There was no difference among the three groups for the proportion of participants having conductive hearing loss.

There is a detrimental impact of reduction in bone mineral density on middle ear transmission characteristics which may go unnoticed initially. Treatment of osteoporosis may potentially mitigate hearing loss from middle ear fractures due to reduced bone mineral density. Absence of significant air-bone gap with the presence of reduced middle ear resonance frequency may be early signs of reduced BMD.