LM406 - Extended High-Frequency Hearing Loss: From Speech Test Materials to Clinical Manifestations

Abstract:
Humans can hear up to 20 kHz; however, audiologists rarely test hearing at extended high frequencies in the clinic. This multi-authored presentation aims to provide evidence-based, comprehensive information on EHF hearing loss that has direct clinical significance. Specifically, we will present (1) the benefits that EHFs provide for speech recognition and whether the popular speech testing materials are useful for assessing EHF loss, (2) potential mechanisms by which EHF loss can affect speech-in-noise recognition, (3) physiologic and electrophysiologic test findings in cases with EHF loss, and (4) clinical case studies highlighting EHF loss in the presence of a normal audiogram.

Summary:
Humans can hear up to 20 kHz. However, current clinical tests do not focus on measuring hearing in the extended high frequencies (EHFs; > 8kHz). This is perhaps due to the assumption that EHFs have no perceptual or clinical significance and/or that EHF hearing loss has no adverse effects on speech-in-noise (SIN) recognition. In this learning module, we will discuss the latest research evidence from our laboratories supporting the clinical assessment of EHF loss. This learning module is organized into four sections: (1) review of speech test materials for EHF loss assessment; (2) mechanisms underlying SIN deficits in listeners with EHF loss; (3) otoacoustic emissions (OAEs) and auditory brainstem response (ABR) results in cases with EHF loss; and (4) individual clinical case studies highlighting EHF loss despite a normal audiogram.

EHFs in speech provide perceptual cues for speech recognition in noise, but many audiological testing materials do not include energy at EHFs. We will discuss the benefits that EHFs provide for speech recognition and review several speech testing materials to examine whether they are useful for testing EHF loss. Following this presentation, audience members will be able to describe the benefits that EHFs provide for speech recognition in noise. They will also be able to identify some popular speech testing materials that do not include EHFs.

Some people with clinically defined normal hearing report difficulty hearing in noise. Substantial evidence in adults and children demonstrates that EHF hearing, beyond the currently tested range of clinical audiometry, contributes to SIN perception. However, the mechanisms underlying this association are not yet clear. Our preliminary data in children and adults suggests three hypotheses: (1) loss of audibility and/or broadened auditory filters at EHFs results in impaired SIN perception; (2) EHF loss is an indicator of damaged outer hair cells outside the EHF range that results in impaired SIN perception; and (3) factors causing EHF loss may also cause deafferentation (e.g., loss of synapses, nerve fibers and/or hair cells), resulting in impaired SIN performance. We will review data collected through multiple studies in our laboratory using standard (0.25-8 kHz) and EHF (9-16 kHz) audiometry, subjective reports of listening difficulties, digits-in-noise test, Bamford-Kowal-Bench-SIN test, double-evoked OAEs with chirp stimuli (0.71-14.7 kHz), and wideband middle-ear muscle reflex in children and adults (7-65 years; N=344).

Listeners with EHF loss may have subclinical cochlear and/or neural deficits in the standard frequencies. We will review distortion-product OAEs and click-ABR results to examine if EHF loss is associated with pre-clinical deficits that may not be reflected in behavioral thresholds but can be identified using objective tests. We will also review clinical audiological testing that was completed in 2021-2022 in the UT Health RGV clinics for various hearing-related complaints (hearing, tinnitus, dizziness, and hyperacusis). Results from patients (14- 43 years) show normal hearing in the 0.25-8 kHz range yet impaired hearing in the EHFs.

Unlike most advancements in research, EHF testing can be relatively easily incorporated into clinical practice. Overall, this learning module will substantially facilitate clinical consensus for testing EHFs.