Optimization and Validation of Electric Acoustic Stimulation (EAS) Mapping as a Function of Residual Hearing After CI-Implantation

Overview

The aim of this clinical study is to investigate how the fitting of an EAS (electrical acoustic stimulation) based on electrocochleography (ECochG) thresholds compares to fitting based on pure tone audiogram thresholds in terms of speech intelligibility in quiet and noise. The personal feedback from the study participants regarding the question of better fitting and the resulting sound quality should also be included in the analysis.

Detailed description

As the indications for Cochlear Implant (CI) Surgery expand to also include hearing impaired patients with some residual hearing in the ipsilateral (to be implanted) ear, residual hearing preservation during the surgical intervention becomes even more important. It is also known from the literature that patients will benefit from having good residual acoustic hearing after CI-Implantation in terms of the sound quality. This is particularly so for speech comprehension in noise as well as for music perception with the CI.

Present-day clinical Sound Processor programming software provides Electric Acoustic Stimulation (EAS) to account for preserved residual hearing. For an optimized EAS fitting, it is postulated here that optimal conditions are achieved when the electric and acoustic stimulation do not overlap. To achieve this, the acoustic stimulation ought to be limited to only regions where there is still useful acoustic hearing, while the electric stimulation should also be restricted to regions where there is no longer significant useful acoustic hearing. In the Maestro clinical software, the threshold for significant useful acoustic hearing is set to 65 dB Hearing Level (HL). This then determines the cut-off frequency between the acoustic and electric stimulation regions.

The standard clinical Maestro software computes this cut-off based on a regular pure tone audiogram (PTA) which has been manually stored in the software. However, it is arguable that this does not always represent an accurate cut-off frequency required for optimal fitting because the audiogram thresholds themselves are subjective in nature and can often vary in a test-retest situation, depending on the attention and reaction times of the patient. It has been reported that the unaided thresholds do not play a significant role in the EAS fitting. In this respect, it may be more accurate and beneficial to use objective measures such as electrocochleography (ECochG) to determine the thresholds of the residual hearing.

The current family of Med-El Cochlear Implants are equipped with the capability to perform ECochG measurements using the implant's own intracochlear electrodes within the scala tympani. The measurements can also be conducted intraoperatively or postoperatively. This intracochlear ECochG feature of the implants therefore allows us to objectively determine the residual hearing thresholds.

The aim of this study is to discuss the advantages of objective fitting of the EAS compared to subjective fitting using a PTA with respect to speech intelligibility in quiet and in noise. The personal feedback from the study participants regarding the question of better fitting and the resulting sound quality should also be included in the analysis.

From the existing literature, it is not expected that there should be any significant gender effects. This also does not belong to the primary aims of this study and we will not be investigating this aspect.

Interventions

• Other The objective fitting method of the EAS based on the thresholds of electrocochleography is the intervention of our study.
  Measured ECochG thresholds will be used in the initial EAS fitting in period 1 for sequence B. For sequence A, the ECochG-based EAS fitting (with up-to-date ECochG thresholds) will take place three months later at the beginning of period 2.
• Other The subjective adjustment of an EAS based on thresholds from the pure tone audiogram.
  The control intervention is the subjective EAS fitting based on PTAs. This is provided to sequence A at the beginning of period 1 baseline and to sequence B at the beginning of period 2.

Primary outcome measures

• Speech Recognition Threshold (SRT50) [Time frame: Three months after EAS fitting]

Secondary outcome measures (3)

• Subjective level of auditory benefit [Time frame: Three months after EAS fitting]
• Subjectively preferred EAS fitting method [Time frame: at the end of the study, six months after baseline]
• Post-operative ECochG and PTA tresholds [Time frame: Three months after EAS fitting (either objective or subjective EAS fitting)]

Eligibility criteria

Inclusion criteria

• Patients aged between 18-85 years.
• Cochlear Implant (CI) candidates with measurable post-operative low-frequency residual hearing (125Hz <65dB, 250Hz <65dB, 500Hz <65dB).
• Only patients with MED-EL EAS.
• Written informed consent must be obtained prior to study start.

Exclusion criteria

• Patients with cognitive impairments who, as a result, lack the capacity to make decisions.
• Uncooperative patients regarding pure tone audiometry thresholds measurements.
• Morbus Menière or intracochlear/ vestibular schwannoma

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

Randomized

Model

Crossover

Masking

Open label

Primary purpose

Other

Study locations

Center list to be confirmed — check the primary protocol.

Publications

• Schaefer S, Sahwan M, Metryka A, Kluk K, Bruce IA. The benefits of preserving residual hearing following cochlear implantation: a systematic review. Int J Audiol. 2021 Aug;60(8):561-577. doi: 10.1080/14992027.2020.1863484. Epub 2021 Jan 10. PMID 33426931
• Rajan G, Tavora-Vieira D, Baumgartner WD, Godey B, Muller J, O'Driscoll M, Skarzynski H, Skarzynski P, Usami SI, Adunka O, Agrawal S, Bruce I, De Bodt M, Caversaccio M, Pilsbury H, Gavilan J, Hagen R, Hagr A, Kameswaran M, Karltorp E, Kompis M, Kuzovkov V, Lassaletta L, Yongxin L, Lorens A, Manoj M, Martin J, Mertens G, Mlynski R, Parnes L, Pulibalathingal S, Radeloff A, Raine CH, Rajeswaran R, Sc PMID 29073844
• 15. Wagener KC, Kühnel V, Kollmeier B (1999b) Entwicklung und Evaluation eines Satztests für die deutsche Sprache III: Evaluation des Oldenburger Sprachtests. Z Audiol 38:86-95.
• Wagener KC, Kühnel V, Kollmeier B (1999a) Entwicklung und Evaluation eines Satztests für die deutsche Sprache I: Design des Oldenburger Satztests. Z Audiol 38:4-15.
• Hey M, Bohnke B, Mewes A, Munder P, Mauger SJ, Hocke T. Speech comprehension across multiple CI processor generations: Scene dependent signal processing. Laryngoscope Investig Otolaryngol. 2021 Jun 15;6(4):807-815. doi: 10.1002/lio2.564. eCollection 2021 Aug. PMID 34401506
• Gifford RH, Sunderhaus LW, Dawant BM, Labadie RF, Noble JH. Cochlear implant spectral bandwidth for optimizing electric and acoustic stimulation (EAS). Hear Res. 2022 Dec;426:108584. doi: 10.1016/j.heares.2022.108584. Epub 2022 Jul 28. PMID 35985964
• Gawliczek T, Mantokoudis G, Anschuetz L, Caversaccio MD, Weder S. Comparison of auditory brainstem response and electrocochleography to assess the coupling efficiency of active middle ear implants. Front Neurol. 2023 Sep 6;14:1231403. doi: 10.3389/fneur.2023.1231403. eCollection 2023. PMID 37745650
• Dillon MT, O'Connell BP, Canfarotta MW, Buss E, Hopfinger J. Effect of Place-Based Versus Default Mapping Procedures on Masked Speech Recognition: Simulations of Cochlear Implant Alone and Electric-Acoustic Stimulation. Am J Audiol. 2022 Jun 2;31(2):322-337. doi: 10.1044/2022_AJA-21-00123. Epub 2022 Apr 8. PMID 35394798

Identifiers

NCT: NCT07476079 · EAS_fitting

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗