Evaluative audiometry after cochlear implant provision.

BACKGROUND: One of the main treatment goals in cochlear implant (CI) patients is to improve speech perception. One of the target parameters is speech intelligibility in quiet. However, treatment results show a high variability, which has not been sufficiently explained so far. The aim of this noninterventional retrospective study was to elucidate this variability using a selected population of patients in whom etiology was not expected to have a negative impact on postoperative speech intelligibility. MATERIALS AND METHODS: Audiometric findings of the CI follow-up of 28 adult patients after 6 months of CI experience were evaluated. These were related to the preoperative audiometric examination and evaluated with respect to a recently published predictive model for the postoperative monosyllabic score. RESULTS: Inclusion of postoperative categorical loudness scaling and hearing loss for Freiburg numbers in the model explained 55% of the variability in fitting outcomes with respect to monosyllabic word recognition. CONCLUSION: The results of this study suggest that much of the cause of variability in fitting outcomes can be captured by systematic postoperative audiometric checks. Immediate conclusions for CI system fitting adjustments may be drawn from these results. However, the extent to which these are accepted by individual patients and thus lead to an improvement in outcome must be subject of further studies, preferably prospective.

The Effects of Stimulus Repetition Rate on Electrically Evoked Auditory Brainstem Potentials in Postlingually Deafened Adult Cochlear Implant Recipients.

Background: By using outcome prediction scores, it is possible to distinguish between good and poor performers with cochlear implants (CI) after CI implantation. The reasons for poor performance, despite good basic conditions, can be manifold. On the one hand, the postoperative fitting may be inadequate; on the other, neurophysiological disease processes may impair speech understanding with a CI. These disease processes are not yet fully understood. In acoustics, it is known that the auditory brainstem responses (ABR) and their latencies and amplitudes allow differential diagnosis based on reference values for normal-hearing individuals. The aim of this study was to provide reference values for electrically evoked brainstem responses (EABRs) in terms of rate-dependent latencies and amplitudes. Methods: 20 ears of 18 experienced adult CI recipients with a predicted and measured good postoperative word recognition score were recruited from the clinic's patient pool. In the same stimulation mode and intensity we measured latencies and interpeak-latencies of EABRs and electrically evoked compound action potentials (ECAPs). With a defined supra-threshold stimulation intensity above the individual ECAP threshold, we applied stimulation at several rates between 11 and 91 stimuli per second. Results: We found rate dependences for EABR latency t3 and t5 in the order of 0.19 ms and 0.37 ms, respectively, while ECAP was not affected by rate. Correspondingly, the interpeak intervals' rate dependences for t5-t1, t5-t3 and t3-t1 were of the order of 0.37 ms, 0.18 ms and 0.19 ms. Comparing the EABR amplitudes between the stimulation rates 11/s and 81/s, we found that at 81/s the amplitudes were significantly reduced down: to 73% for A3 and 81% for A5. These rate dependences of latency and amplitude in EABR have characteristics comparable to those of acoustic ABR. Conclusions: These data may serve to provide reference values for EABR and ECAP latencies, interpeak intervals and amplitudes with respect to stimulation rate. Altered response patterns of ECAPs and EABRs to normalised stimulation modes could be used in the future to describe and classify neuropathological processes in a better-differentiated way.

[Evaluative audiometry after cochlear implant provision. German Version]. / Zur evaluierenden Audiometrie nach Cochlea-Implantat-Versorgung.

BACKGROUND: One of the main treatment goals in cochlear implant (CI) patients is to improve speech perception. One of the target parameters is speech intelligibility in quiet. However, treatment results show a high variability, which has not been sufficiently explained so far. The aim of this noninterventional retrospective study was to elucidate this variability using a selected population of patients in whom etiology was not expected to have a negative impact on postoperative speech intelligibility. MATERIALS AND METHODS: Audiometric findings of the CI follow-up of 28 adult patients after 6 months of CI experience were evaluated. These were related to the preoperative audiometric examination and evaluated with respect to a recently published predictive model for the postoperative monosyllabic score. RESULTS: Inclusion of postoperative categorical loudness scaling and hearing loss for Freiburg numbers in the model explained 55% of the variability in fitting outcomes with respect to monosyllabic comprehension. CONCLUSION: The results of this study suggest that much of the cause of variability in fitting outcomes can be captured by systematic postoperative audiometric checks. Immediate conclusions for CI system adjustments may be drawn from these results. However, the extent to which these are accepted by individual patients and thus lead to an improvement in outcome must be subject to further study, preferably prospective.

[Suitability of determining percentage hearing loss for monitoring cochlear implant rehabilitation]. / Eignung der Bestimmung prozentualer Hörverluste zum Monitoring der Cochlea Implantat Rehabilitation.

BACKGROUND: Calculation of percentage hearing loss (pHV) from the pure-tune audiogram according to Röser in 1973 or from the speech audiogram according to Boenninghaus and Röser in 1973 is a method still applied for quantitative assessment of hearing. However, this is not common for the evaluation of postoperative results of implantable hearing systems. During the regular work-up after cochlear implantation (CI) in Germany, all necessary parameters are available for calculation of pHV either from categorical loudness scaling (pHVKLS) or speech-recognition threshold (pHVFB). OBJECTIVE: The parameters pHVKLS and pHVFB are introduced and calculated from data available from clinical routine. Their potential applicability for assessment of the result of CI is evaluated. MATERIALS AND METHODS: This study comprises retrospective chart review of audiological parameters from 66 CI procedures in one tertiary referral center. pHVKLS was calculated from the equal loudness curve 5 CU, pHVFB from the Freiburg speech test in free field. RESULTS: While pHVKLS shows small variation, the variation in pHVFB is initially larger but decreases over time. Furthermore, starting from initial fitting, the mean pHV shows convergence over time. The difference between pHVFB and pHVKLS is positive and statistically significant. CONCLUSION: It is possible to calculate pHVKLS and pHVFB from routine data. A correlation of the difference between pHVFB and pHVKLS with successful CI performance seems plausible.

[OLSA level control in monaural speech audiometry in background noise for the evaluation of the CI fitting result]. / OLSA-Pegelsteuerung bei monauraler Sprachaudiometrie im Störschall zur Evaluation des CI-Versorgungsergebnisses.

SCIENTIFIC BACKGROUND: Speech audiometry measurements under the influence of background noise are a fundamental part of evaluating the outcome of hearing care. As yet far, there are no recommendations for selecting a suitable method for adaptive speech audiometry measurements in background noise in cochlear implant (CI) care, so either the choice the adaptive level change of the speech signal (S) with constant noise (N) or the adaptive level change of N with constant S. OBJECTIVES: Do the measurement results of the monaural speechrecognition threshold in noise (SRT) with the Oldenburg Sentence Test (OLSA) depend on the choice of level control? MATERIAL AND METHODS: A total of 50 series of measurements with OLSA in noise and the Freiburg speech intelligibility test in quiet (FBE) on middle-aged CI patients from clinical routine. RESULTS: There is no significant difference in the measurement results with different level controls when the SRT is less than 5 [Formula: see text]. Below 55 % monosyllabic intelligibility in quiet, the SRT in noise becomes greater than 5 [Formula: see text]. CONCLUSION: From a clinical, audiological and methodological point of view, it is advisable to carry out the adaptive monaural speech intelligibility measurement with a constant speech signal at 65 [Formula: see text].

Intraoperative quantification of floating mass transducer coupling quality in active middle ear implants: a multicenter study.

PURPOSE: Evaluating the effectiveness of intraoperative auditory brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant for quantifying the implant's floating mass transducer (FMT) coupling quality. METHODS: In a diagnostic multicentric study, patients (> 18 years) who received a VSB with different coupling modalities were included. Pre- and postoperative bone conduction thresholds, intraoperative VSB-evoked ABR thresholds (VSB-ABR) using a modified audio processor programmed to preoperative bone conduction thresholds, postoperative vibrogram thresholds, and postoperative VSB-ABR thresholds were measured. Coupling quality was calculated from the difference between the pure tone average at 1000, 2000, and 4000 Hz (3PTA) vibrogram and postoperative 3PTA bone conduction thresholds. RESULTS: Twenty-three patients (13 males, 10 females, mean age 56.6 (± 12.5) years) were included in the study. Intraoperative VSB-ABR response thresholds could be obtained in all except one patient where the threshold was > 30 dB nHL. Postoperatively, an insufficient coupling of 36.7 dB was confirmed in this patient. In a Bland-Altman analysis of the intraoperative VSB-ABRs and coupling quality, the limits of agreement exceeded ± 10 dB, i.e., the maximum allowed difference considered as not clinically important but the variation was within the general precision of auditory brainstem responses to predict behavioral thresholds. Five outliers were identified. In two patients, the postoperative VSB-ABR thresholds were in agreement with the coupling quality, indicating a change of coupling before the postoperative testing. CONCLUSION: The response thresholds recorded in this set-up have the potential to predict the VSB coupling quality and optimize postoperative audiological results.

Intraoperatives Tip-Foldover-Screening mittels Spread of Excitation Messungen.

BACKGROUND: In rare cases, a cochlear implantation can lead to a so-called tip fold-over during insertion of the electrode array. In order to detect or exclude such a misalignment a radiological check of the cochlear implant (CI) electrode array is carried out intra- or often post-operatively (gold standard), thereby exposing the patient to additional radiation. Alternatively, successful electrode insertion can be verified by measuring the spread of excitation (SOE). However, interpretation of the test results requires considerable expertise, and standardized measurement protocols and reference values are also essential. Therefore, the aim of the study is to evaluate an automated screening procedure in order to obtain a reliable statement about the normal tonotopic position of the implanted CI electrode array intraoperatively and with as little effort as possible. METHODS: For CI surgery with Cochlear™ Nucleus® implants, an intraoperative tip-fold-over (TFO) screening was performed in a bi-centric study in over 100 adult patients: Firstly, threshold measurements for electrically evoked compound action potential (ECAP) using AutoNRT™ were recorded. Subsequently, SOE measurements were carried out on electrodes 13 and 22. The automated evaluation of the SOE data sets then made it possible to make a dichotomous decision about a normal or abnormal test result. The position of the electrode array was checked intra- or post-operatively using conventional transorbital X-ray (reference method). RESULTS: The intraoperative TFO screening procedure is applicable in around 80% of cases. The accuracy of the screening for measurements via the active stimulation electrodes 13 / 22 is 63.9% / 95.4%. The classification error is 36.1% / 4.6% and the phi coefficient is 0.27 / 0.69. All radiologically proven tip-fold-overs were reliably identified with the intraoperative screening (sensitivity = 100%). A higher specificity (>95%) can be achieved only with measurements via electrode 22. CONCLUSIONS: The TFO Screening via measurement at electrode 22 can successfully distinguish between a correct and incorrect position of the electrode array due to a tip-fold-over, and the remaining cases would require further imaging.

Active Middle Ear Implant Evoked Auditory Brainstem Response Intensity-Latency Characteristics.

OBJECTIVE: To analyze intensity-latency functions of intraoperative auditory evoked brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant with respect to coupling efficiency, VSB evoked ABR thresholds, and coupling modality [oval window (OW) placement vs. Incus placement and vs. round window (RW) placement]. STUDY DESIGN: Exploratory study. SETTING: Bi-centric study at tertiary referral centers. PATIENTS: Twenty-four patients (10 female, 14 male, mean age: 58 years) who received a VSB. OUTCOME MEASURES: Wave-V intensity-latency functions of intraoperative VSB evoked ABRs using a modified audio processor programmed to preoperative bone conduction thresholds for stimulation. Threshold level correction to coupling efficiency and ABR thresholds. Individual plots and exponential function fits. RESULTS: After ABR threshold level correction, the latency functions could be aligned. A large variance of latencies was observed at individual threshold level. Wave-V latency was longest in the Incus placement subgroup (9.73 ms, SD: 1.04) as compared to OW placement subgroup (9.47 ms, SD: 1.05), with the shortest latency in the RW placement subgroup (8.99 ms, SD: 0.68). For increasing stimulation levels, the variance decreased with intensity-latency function slopes converging toward a steady-state (saturation) latency caused by saturation of audio processor (stimulation) gain. Latency saturation was reached at a stimulation level of 50 dB nHL for the OW placement subgroup, 35 dB nHL for the Incus placement subgroup, and 30 dB nHL for the RW placement subgroup. The latency and saturation results indicated decreased dynamic range for RW placement, i.e., reverse stimulation. CONCLUSIONS: VSB evoked ABR wave-V intensity-latency function slopes were similar to acoustic stimulation at high stimulation levels with a shift toward longer latencies caused by audio processor signal delay. Saturation of latencies occurred for higher stimulation levels due to saturation of audio processor gain. Thus, the analysis of VSB evoked intensity-latency functions appears to allow for the objective assessment of a patient's individual dynamic range. This can further improve diagnostics as well as intraoperative and postoperative quality control.

Slope of electrically evoked compound action potential amplitude growth function is site-dependent.

OBJECTIVES: In human cochlear implant (CI) recipients, the slope of the electrically evoked compound action potential (ECAP) amplitude growth function (AGF) is not very well investigated, in comparison to the threshold derived from the AGF. This is despite the fact that it was shown in animal experiments that the slope correlates with the number of excitable neurons. The rationale of this study was to establish baseline data of the AGF slope for possible clinical applications, while investigating stability over time and dependence on cochlear site. DESIGN: ECAP AGFs of 16 ears implanted with MED-EL CIs were recorded on all electrode contacts during the normal clinical routine at 4 different points in time. RESULTS: Due to patient availability, not all 16 ears could be measured at all 4 points in time. A dependence of the slope on the electrode position was visible and statistically significant: At the three electrode contacts at the apical end of the array, the slope is greater compared to the medial and basal region of the cochlea. CONCLUSION: The three most apical electrode contacts show greater slopes of ECAP AGF recordings. Our data of the cohort slopes show mild effects between the 4 different points in time.

Intraoperative Recording of Auditory Brainstem Responses for Monitoring of Floating Mass Transducer Coupling Efficacy During Revision Surgery-Proof of Concept.

OBJECTIVE: The objective of the study was to measure auditory brainstem responses elicited by stimulation via a semi-implantable active middle ear implant with an electromagnetically driven floating mass transducer to quantify the coupling efficacy (=vibroplasty in situ thresholds - bone conduction thresholds) in a patient during a revision surgery. PATIENTS: One patient, reimplanted with an active middle ear implant in a revision surgery. INTERVENTION(S): Diagnostic. MAIN OUTCOME MEASURE(S): Intraoperative auditory brainstem responses evoked by stimulation via an active middle ear implant in a calibrated set-up directly indicating the coupling efficacy magnitude (auditory brainstem response threshold = coupling efficacy), as well as pre- and postoperative bone conduction and vibroplasty in situ thresholds. RESULTS: The intraoperative auditory brainstem response threshold was detected at 0 dB nHL, i.e., the magnitude of coupling efficacy was determined intraoperatively to be 0 dB. The actual postoperative coupling efficacy (=postoperative vibroplasty in situ - postoperative bone conduction thresholds) was -2.5 dB. CONCLUSIONS: The coupling efficacy determined intraoperatively was consistent with the postoperative coupling efficacy. The described method seems to be a promising tool to objectively quantify the magnitude of coupling efficacy in active middle ear implant surgeries.

Excitation characteristic of a bipolar stimulus for broadband stimulation in measurements of electrically evoked auditory potentials.

OBJECTIVE: The aim of this study was to determine the optimum electrical stimulation mode for the measurement of electrically evoked potentials. To quantify the broadband excitation electrically evoked compound action potentials were recorded in cochlear implant recipients. The full width half maximum was determined for spread of excitation along the electrode array. DESIGN: Prospective clinical study. STUDY SAMPLE: The study sample consisted of 20 adult cochlear implant users. RESULTS: The applied alternating, intracochlear stimulation mode leads to neural excitation along approximately 80% of the length of the electrode array. The median of the full width at half maximum values covered the range of 18 electrodes on the implant array. CONCLUSION: The bipolar, alternating, and intracochlear stimulation mode would provide a sufficient, broadband excitation of the spiral ganglion to measure electrically evoked auditory potentials.

The Role of Auditory Evoked Potentials in the Context of Cochlear Implant Provision.

: Auditory evoked potentials (AEP) are highly demanded during the whole process of equipping patients with cochlear implants (CI). They play an essential role in preoperative diagnostics, intraoperative testing, and postoperative monitoring of auditory performance and success. The versatility of AEP's is essentially enhanced by their property to be evokable by acoustic as well as electric stimuli. Thus, the electric responses of the auditory system following acoustic stimulation and recorded by the conventional surface technique as well as by transtympanic derivation from the promontory (Electrocochleography [ECochG]) are used for the quantitative determination of hearing loss and, additionally, electrically evoked compound actions potentials (ECAP) can be recorded with the intracochlear electrodes of the implant just adjacent to the stimulation electrode to check the functional integrity of the device and its coupling to the auditory system. The profile of ECAP thresholds is used as basis for speech processor fitting, the spread of excitation (SOE) allows the identification of electrode mislocations such as array foldover, and recovery functions may serve to optimize stimulus pulse rate. These techniques as well as those relying on scalp surface activity originating in the brainstem or the auditory cortex accompany the CI recipient during its whole life span and they offer valuable insights into functioning and possible adverse effects of the CI for clinical and scientific purposes.

A New Score to Predict the Risk of Hearing Impairment After Microvascular Decompression for Hemifacial Spasm.

BACKGROUND: Intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) has been implemented to reduce the risk of hearing impairment during microvascular decompression for hemifacial spasm. OBJECTIVE: To evaluate intraoperative monitoring of BAEPs during microvascular decompression in patients with hemifacial spasm for predicting the risk of hearing impairment after surgery. METHODS: This prospective study included 100 patients. BAEPs were recorded for all patients. We established a scoring system for the changes in wave I amplitude, I-III interpeak latency, and wave V amplitude and latency. For each change, total points were calculated, and a score out of 6 was assigned to every patient. We classified the patients based on the points scored into 3 risk groups: low-risk (0-3), medium-risk (4-5), and high-risk (6). Further, the correlation between the score and the hearing outcome was evaluated to detect the incidence and degree of hearing impairment. RESULTS: Eighty-seven patients scored 0 to 3, 10 scored 4 to 5, and 3 scored 6. The degree of hearing impairment was proportionate to the score recorded at the end of surgery, and patients in the low-risk group showed no impairment; medium-risk group, deterioration of maximum 2 grades according to World Health Organization classification of hearing impairment; and high-risk group, deterioration of 3 to 4 grades. CONCLUSION: Intraoperative monitoring of BAEPs evaluated through our scoring system was valuable in predicting hearing impairment after surgery.

Influence of Floating-Mass Transducer Coupling Efficiency for Active Middle-Ear Implants on Speech Recognition.

OBJECTIVE: The efficiency of vibroplasty (coupler-floating mass transducer [FMT] assembly) can be monitored by direct stimulation of the inner ear through the active middle-ear implant system and comparison of the vibroplasty in vivo threshold and the postoperative bone-conduction pure-tone threshold. The aim of this study was to compare the vibroplasty in vivo threshold with the postoperative speech recognition in patients with a high preoperative maximum word recognition score. STUDY DESIGN: Retrospective cohort study of German-speaking patients implanted with a vibrating ossicular prosthesis (VORP) 502 or VORP 503 and high preoperative maximum word recognition score between the years of 2011 and 2015. SETTING: Multicenter study of four German centers. PATIENTS: Twenty-three active middle-ear implant users. INTERVENTION: Rehabilitative. MAIN OUTCOME MEASURES: Bone-conduction pure-tone and vibroplasty thresholds, postoperative aided word recognition score (WRS) at 65 dB SPL (sound pressure level) and preoperative maximum WRS with Freiburg monosyllabic words. RESULTS: The mean postoperative aided WRS at 65 dB SPL was 82%. An increasing difference between vibroplasty thresholds and bone-conduction thresholds was associated with a higher discrepancy between the unaided maximum WRS and the postoperative aided WRS. Only if this difference was less than 20 dB, an articulation index of 0.5 (WRS = 75%) or more was achieved. CONCLUSIONS: Audiological outcome after vibroplasty depends on the coupling efficiency reflected by the vibroplasty threshold.