ECG of the Inner Ear: Establishment of the Short-pulse DPOAE for the Detection of Ototoxicity

• Applicant: Dr. Katharina Bader
• Subject Area: Otolaryngology, Phoniatrics and Audiology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 469837692

To date, there is no international consensus on monitoring ototoxicity in a standardized manner. In 2009, the American Academy of Audiology evaluated pure-tone audiometry (PTA), especially in the high frequency range (HFA) and distortion-product otoacoustic emissions (DPOAE) as the most reliable methods. In 2019, a joint recommendation was made by the “International Late Effects of Childhood Cancer Guideline Harmonization Group” in collaboration with the European “PanCare Consortium“ to include anamnesis, PTA for the frequencies 1 – 8 kHz, DPOAE and tympanometry for the evaluation of ototoxicity in children and adolescents. Ideally, ototoxicity monitoring should be performed using multiple methods, as single methods are not sufficiently informative.Based on moderate-evidence studies, DPOAE and HFA detect changes in hearing earlier and with greater sensitivity than PTA. Conventional DPOAE stimulus- and analysis methods use continuous stimulus tones, which cannot distinguish between the two DPOAE source components and can erroneously influence DPOAE signal detection by interference. At the ENT department in Tübingen, the separation of the two main DPOAE source components with the analysis of the DPOAE signal in the time domain and using pulsed stimulus tones was established and further developed. So-called short-pulse DPOAEs allow by the usage of DPOAE input-output functions precise and time-efficient estimates of hearing thresholds (EDPTs). The combined use of short-pulse DPOAEs and individual optimum primary tone levels in DPOAE level maps showed in recent studies not only a further improvement in accuracy for frequencies 1 – 14 kHz, but also a lower variability of EDPTs for high frequencies compared to PTA.In the proposed project, we aim to further develop DPOAE level maps based on short-pulse DPOAE as an analytical tool of the cochlear amplifier and establish it in patients receiving radio-chemotherapy. The characterization of high frequency DPOAE and the dynamic range of the cochlear amplifier for different frequencies as well as the implementation of a modern FPL-EPL calibration are essential preparatory steps. Furthermore, it is necessary to evaluate EDPTs based on DPOAE level maps in a hearing impaired patient population and to adapt them if necessary before short-pulse DPOAE and hearing threshold estimates based on them are applied in close time intervals in patients receiving radio-chemotherapy.The goal of the proposed project is to assess the sensitivity of EDPTs compared to RTA and conventional DPOAE, quantify differences in amplitude and latency of individual DPOAE source components using single short-pulse DPOAE signals, and investigate longitudinal changes in DPOAE level maps and their parameters. If successful, short-pulse DPOAE can act as a time-efficient, easily clinically applicable analysis tool of the inner ear and detect degeneration or even regeneration of the cochlear amplifier early and sensitively.

• DFG Programme: Research Grants