[Retrocochlear diagnostics for acute hearing loss and successful therapy]. / Retrocochleäre Diagnostik im Rahmen der Hörsturzuntersuchung und erfolgreiche Therapie.

A 41-year-old female patient presented due to acute onset of unilateral hearing loss 3 months previously and persistent since then. Systemic therapy with oral glucocorticoids in decreasing doses had been performed beforehand, but did not lead to any improvement. In the course of audiological diagnostics, based on subjective and objective methods, a retrocochlear hearing disorder was suspected. A meningioma was diagnosed by diagnostic imaging. Subsequent surgical removal achieved a significant hearing improvement.

Evaluation of CI electrode position from imaging: comparison of an automated technique with the established manual method.

BACKGROUND: A manual evaluation of the CI electrode position from CT and DVT scans may be affected by diagnostic errors due to cognitive biases. The aim of this study was to compare the CI electrode localization using an automated method (image-guided cochlear implant programming, IGCIP) with the clinically established manual method. METHODS: This prospective experimental study was conducted on a dataset comprising N=50 subjects undergoing cochlear implantation with a Nucleus® CI532 or CI632 Slim Modiolar electrode. Scalar localization, electrode-to-modiolar axis distances (EMD) and angular insertion depth (aDOI) were compared between the automated IGCIP tool and the manual method. Two raters made the manual measurements, and the interrater reliability (±1.96·SD) was determined as the reference for the method comparison. The method comparison was performed using a correlation analysis and a Bland-Altman analysis. RESULTS: Concerning the scalar localization, all electrodes were localized both manually and automatically in the scala tympani. The interrater differences ranged between ±0.2 mm (EMD) and ±10° (aDOI). There was a bias between the automatic and manual method in measuring both localization parameters, which on the one hand was smaller than the interrater variations. On the other hand, this bias depended on the magnitude of the EMD respectively aDOI. A post-hoc analysis revealed that the deviations between the methods were likely due to a different selection of mid-modiolar axis. CONCLUSIONS: The IGCIP is a promising tool for automated processing of CT and DVT scans and has useful functionality such as being able to segment the cochlear using post-operative scans. When measuring EMD, the IGCIP tool is superior to the manual method because the smallest possible distance to the axis is determined depending on the cochlear turn, whereas the manual method selects the helicotrema as the reference point rigidly. Functionality to deal with motion artifacts and measurements of aDOI according to the consensus approach are necessary, otherwise the IGCIP is not unrestrictedly ready for clinical use.

[Extended preoperative speech audiometric diagnostics for cochlear implant treatment]. / Erweiterte präoperative sprachaudiometrische Diagnostik im Rahmen der Cochleaimplantatversorgung.

BACKGROUND: For severe hearing loss and even profound deafness, cochlear implants (CIs) have become the treatment of choice. For establishment of the CI indication, the preoperative Freiburger monosyllabic word recognition (EV) at 65 dB SPL in free field with a hearing aid (EVHG65) and the maximal understanding (mEV) without a hearing aid with headphones results are important. The goal of this retrospective study was to analyse the correlation of word recognition with a hearing aid at 80 dB SPL (EVHG80) and mEV. This represents an extension to measuring EVHG65 compared to mEV and to pure-tone audiometry (4FPTA). METHODS: In this study, word recognition with and without a hearing aid was retrospectively analysed for 661 ears. Inclusion criterium was CI implantation at a later date. RESULTS: During preoperative CI diagnostics, an mEV of 0% was found in 334 ears. The EVHG65 for 485 ears and the EVHG80 for 335 ears were also 0%. The EV with hearing aid was found to worsen with increasing 4FPTA at both sound pressure levels, although this effect was smaller at 80 dB SPL than at 65 dB SPL. Including only ears with mEV > 0 % (N = 260 ears), a stronger correlation between EVHG80 and mEV with a difference of (-4.0 ± 16.4%) in comparison to EVHG65 and mEV with a difference of (-18.3 ± 16.7%) is seen. This shows a significant difference between mEV and EVHG80 compared to mEV and EVHG65. CONCLUSION: At a sound pressure level of 65 dB SPL, EV with hearing aid often does not show the accordance with mEV specified by hearing aid and CI guidelines. The EVHG80 correlates better with mEV than EVHG65. For clinical diagnosis it is rational to measure speech discrimination with hearing aid at levels higher than 65 dB SPL.

Facilitation properties in electrically evoked compound action potentials depending on spatial location and on threshold.

Spiral ganglion neurons (SGNs) facilitation properties can be recorded utilizing electrically evoked compound action potential (ECAP). While intracochlear variation of the ECAP threshold in relation to its electrode channel is reported, no study investigated its impact on facilitation. In this study, we quantified intracochlear variation of the facilitation properties in cochlear implants (CI) using ECAPs. We hypothesized that the facilitation effect is dependent on the electrode channel and its ECAP threshold. Therefore, ECAPs were recorded in 23 CI subjects. For each subject, five default (channel-derived) and up to two additional (threshold-derived) stimulation sites were defined. Facilitation was quantified by the paradigm introduced by (Hey et al., 2017) with optimized parameter settings. For each channel the maximum facilitated amplitude was determined by a series of ECAP measurements. A linear mixed-effects model was used to investigate the impact of the electrode channel and ECAP threshold on the maximum facilitated amplitude. The maximum facilitated amplitude was found to be dependent on the ECAP threshold and independent on the electrode channel. We conclude that the facilitation paradigm is a useful and feasible tool to gain local information on the SGNs temporal processing patterns.

Optimizing the efficiency of ECAP measurements due to interpolation.

BACKGROUND: Thresholds of electrically evoked compound action potentials (TECAP) may serve as starting points for electrophysiologically based fitting of cochlear implants. Absent TECAP data at single electrodes reduces the number of data points available for fitting and can be substituted by interpolation of measured data points. AIM: To compare complete TECAP profiles with interpolated TECAP profiles of 5/22 (∼22.7%) and 11/22 (50%) electrode contacts. MATERIAL AND METHODS: Single-centre, retrospective, observational study of data from 624 ears implanted with a Slim Modiolar (CI ×32) or Contour Advance (CI ×12, CI24RE(CA)) electrode array (Cochlear Ltd). The deviation of the complete measured TECAP profile from the same profile with missing and therefore interpolated TECAP values was quantified. RESULTS: Interpolated TECAP profiles significantly differ from complete measured profiles especially at the basal and apical electrodes. Reference data for Slim Modiolar and Contour Advance electrodes mean profiles are provided. CONCLUSIONS AND SIGNIFICANCE: Reducing the number of measured TECAP electrodes has to be weighted against losses in the TECAP accuracy of interpolated values. A clinically acceptable compromise may be a reduction from 22 to 11 even non-equidistant data points. While reducing ECAP measurement time, it is accompanied by a minimal loss of accuracy of the TECAP threshold profile.

Quality-assured training in the evaluation of cochlear implant electrode position: a prospective experimental study.

BACKGROUND: The objective of this study was to demonstrate the utility of an approach in training predoctoral medical students, to enable them to measure electrode-to-modiolus distances (EMDs) and insertion-depth angles (aDOIs) in cochlear implant (CI) imaging at the performance level of a single senior rater. METHODS: This prospective experimental study was conducted on a clinical training dataset comprising patients undergoing cochlear implantation with a Nucleus® CI532 Slim Modiolar electrode (N = 20) or a CI512 Contour Advance electrode (N = 10). To assess the learning curves of a single medical student in measuring EMD and aDOI, interrater differences (senior-student) were compared with the intrarater differences of a single senior rater (test-retest). The interrater and intrarater range were both calculated as the distance between the 0.1th and 99.9th percentiles. A "deliberate practice" training approach was used to teach knowledge and skills, while correctives were applied to minimize faulty data-gathering and data synthesis. RESULTS: Intrarater differences of the senior rater ranged from - 0.5 to 0.5 mm for EMD and - 14° to 16° for aDOI (respective medians: 0 mm and 0°). Use of the training approach led to interrater differences that matched this after the 4th (EMD) and 3rd (aDOI) feedback/measurement series had been provided to the student. CONCLUSIONS: The training approach enabled the student to evaluate the CI electrode position at the performance level of a senior rater. This finding may offer a basis for ongoing clinical quality assurance for the assessment of CI electrode position.

Artificial Polysialic Acid Chains as Sialidase-Resistant Molecular-Anchors to Accumulate Particles on Neutrophil Extracellular Traps.

Neutrophils are involved in numerous immunological events. One mechanism of neutrophils to combat pathogens is the formation of neutrophil extracellular traps (NETs). Thereby, neutrophils use DNA fibers to form a meshwork of DNA and histones as well as several antimicrobial components to trap and kill invaders. However, the formation of NETs can lead to pathological conditions triggering among other things (e.g., sepsis or acute lung failure), which is mainly a consequence of the cytotoxic characteristics of accumulated extracellular histones. Interestingly, the carbohydrate polysialic acid represents a naturally occurring antagonist of the cytotoxic properties of extracellular histones. Inspired by polysialylated vesicles, we developed polysialylated nanoparticles. Since sialidases are frequently present in areas of NET formation, we protected the sensitive non-reducing end of these homopolymers. To this end, the terminal sialic acid residue of the non-reducing end was oxidized and directly coupled to nanoparticles. The covalently linked sialidase-resistant polysialic acid chains are still able to neutralize histone-mediated cytotoxicity and to initiate binding of these polysialylated particles to NET filaments. Furthermore, polysialylated fluorescent microspheres can be used as a bioanalytical tool to stain NET fibers. Thus, polySia chains might not only be a useful agent to reduce histone-mediated cytotoxicity but also an anchor to accumulate nanoparticles loaded with active substances in areas of NET formation.