Voluntary increase of acoustic middle ear impedances with simultaneous sound attenuation associated with mild hyperacusis (VIMH)

Background: Acoustic impedances, as measured with tympanometers, change with the pressure in the middle ears, or reflexively as a response to a range of stimuli. A few persons are able to influence their acoustic impedances voluntarily. Aims/objectives: To describe this phenomenon and its clinical consequences. Material and methods: Presentation of five case reports with measurements of the acoustic impedances, hearing thresholds, and otoacoustic emissions (TEOAE) in the relaxed state and while the change in acoustic impedance was invoked. Results: All five subjects were able to voluntarily increase the acoustic impedance of their ears for short periods of time. While the change was active, TEOAE levels decreased by 0.8–9.7 dB and a mild transient conductive hearing loss in the low frequencies occurred. Four out of the five subjects reported a mild hyperacusis when the voluntary change was not invoked and showed unusual features in their acoustically evoked reflex. Conclusions and significance: Subjects who can control their acoustic impedances voluntarily seem to have an increased prevalence of mild hyperacusis. Our results suggest interference of the voluntary control with the acoustic stapes reflex as a mechanism and we propose to name this phenomenon ‘Voluntary Impedance increase with Mild Hyperacusis’, or VIMH.