Hearing Aid Treatment in Patients with Mixed Hearing Loss. Part I: Expected Benefit and Limitations after Stapes Surgery

Abstract

Objective:The purpose of the present study was to determine the fraction of patients with mixed hearing loss who can or cannot expect benefit from power hearing aids (HAs) after stapes surgery. Design: The audiological outcome of 374 stapes surgeries was used to calculate the patients' individual postoperative requirements in terms of gain and output of HAs. These requirements were compared to the available gain and output provided by state-of-the-art power HAs at 0.5, 1.0, 2.0, and 4.0 kHz. According to these comparisons, ears were divided into three groups. For G0, required gain and output lay within the corresponding technical limits of the HAs at all frequencies. In G1, one or both requirements could not be fulfilled at 1 frequency. G2 combined all ears where the requirements lay beyond the HA's technical limitations at 2 or more frequencies. Results: Stapes surgery resulted in an improvement of air-bone gap (ABG) in 84.5% of the cases by 15.7 dB on average. Based on pure-tone average (0.5, 1.0, 2.0, 4.0 kHz), 40.6% of all cases showed an ABG ≤10 dB. 44.9% of all cases did no longer need a HA after stapes surgery. A power HA would fulfill both audiological criteria at all 4 frequencies in 81.6% of cases that needed a HA postoperatively. However, 18.4% would not be sufficiently treatable at 1 or more frequencies (15.0% in G1, 3.4% in G2). Conclusions:The present study identified a subset of patients with mixed hearing loss after stapes surgery that cannot be treated sufficiently with available power HAs. As the residual ABG is an important reason for this lack of treatment success, the advancement of alternative hearing devices that circumvent the middle ear, such as powerful active middle ear implants, is indicated.

Hearing Aid Treatment for Patients with Mixed Hearing Loss. Part II: Speech Recognition in Comparison to Direct Acoustic Cochlear Stimulation

“…Initially, only patients with (surgically treated or untreated) otosclerosis were invited; owing to the low numbers, patients with an ABG of different origin (surgically treated or not) were invited as well. In contrast to part I [Wardenga et al, 2020], where the selection was done based on pathology to provide a representative cohort of patients seen at our clinic, the selection of patients here was performed based on the severity of the hearing loss to provide a cohort that covers the range where conventional hearing aids reach their potential limits.…”

“…To determine whether the hearing device could satisfy the audiological needs of an individual patient, two decision criteria were defined as introduced before by Wardenga et al [2020]. In short, speech presented at a normal conversational level must be audible, which can be translated into a required gain for proper hearing aid fitting.…”

“…In short, speech presented at a normal conversational level must be audible, which can be translated into a required gain for proper hearing aid fitting. The required gain should comprise full compensation of the conductive part and approximately half of the sensorineural component (for details, see part I [Wardenga et al, 2020]). As a second criterion, the MPO of the hearing aid should be high enough to cover the patient's dynamic range of hearing, with a minimum of 35 dB [Zwartenkot et al, 2014;van Barneveld et al, 2018], resulting in a required output (see Table 2 for the applied criteria).…”

“…Hearing aid provision and fitting in patients with mixed hearing loss is not straightforward. Following prescription rules, in principle, full compensation of the airbone gap (ABG) is required, as well as a substantial proportion of the sensorineural component [Wardenga et al, 2020]. Therefore, for treatment of mixed hearing loss, hearing aids have to be powerful in terms of output and stable gain.…”

“…Moreover, such power hearing aids have a limited bandwidth. Especially in the high frequencies, the available gain is limited, as is illustrated in the accompanying paper [Wardenga et al, 2020]: the available gain at 4 kHz of powerful state-of-the-art (SOTA) hearing aids is approximately 20 dB below that at 1 kHz (see Table 1a in Wardenga et al [2020]). Dillon [2012] (in chapter 10) argued that for patients with severe, pure sensorineural hearing loss (the main target group for power hearing aids), decreased high-frequency amplification might be beneficial as most patients might have hearing loss that is sloping, with the poorest hearing in the high-frequency range.…”