Stapedius Reflex Threshold Research Articles

Electrically Evoked Stapedius Reflex Measurements in Cochlear Implantation and its Application in the Postoperative Fitting Process.

Measuring the electrically evoked stapedius reflex during the fitting of cochlear implants (CIs) provides a reliable estimation of maximum comfort levels, resulting in the programming of the CI with high hearing comfort and good speech understanding. Detection of the stapedius reflex and the required stimulation level on each implant channel is already being performed during surgery, whereby intraoperative stapedius reflexes are observed through the surgical microscope. Intraoperative stapedius reflex detection is both an indicator that the auditory nerve is responding to electrical stimulation up to the brainstem and a test for the ability to perform postoperative stapedius reflex measurements. Postoperative stapedius reflex thresholds can be used to estimate upper stimulation levels in the CI fitting process. In particular, in children or patients unable to provide feedback on loudness perception, this method avoids inadequate stimulation with the CI, which can result in poor hearing performance. In addition, overstimulation can be avoided, which could even lead to refusal to use the device.

Comparison of electrically evoked stapedial reflexes in patients with cochlear implants surgically implanted using Veria and posterior tympanotomy approaches.

The study aimed to compare ipsilateral and contralateral electrically evoked stapedial reflex thresholds in children with a unilateral cochlear implant surgically implanted either through Veria or posterior tympanotomy approaches. Forty-nine children using cochlear implants were studied, of whom 27 underwent the Veria approach and 22 underwent the posterior tympanotomy approach. The electrically evoked stapedius reflex thresholds were measured ipsilaterally and contralaterally by stimulating four equally spaced electrodes. The ipsilateral electrically evoked stapedius reflex threshold was absent in all four electrodes in the children implanted using the Veria approach. However, the ipsilateral electrically evoked stapedius reflex threshold was present in 70 per cent of the children implanted using the posterior tympanotomy approach. The contralateral electrically evoked stapedius reflex threshold was present in most of the children for both surgical approaches. The presence of the ipsilateral electrically evoked stapedius reflex threshold varies depending on the surgical technique used for cochlear implantation. However, contralateral reflexes are present in the majority of children using cochlear implants, irrespective of the surgical approach.

Stapedius reflex thresholds obtained in a free sound field as an indicator for over- and understimulation in cochlear implant listeners

Objective The goal of this study was to determine open field stapedius reflex thresholds (oSRTs) in CI patients with fittings based on subjective loudness ratings. A further objective was to compare these oSRTs and those of eSRT-based fittings that are similar to the oSRTs of normal hearing. Design Impedance measurements of the ear drum were taken while subjects were wearing their audio processors. The stapedius reflex was elicited by electrical stimulation transmitted through the activated CI system in response to an acoustic stimulus presented in the free sound field. Study sample Subjects were 50 experienced CI users (n = 57 ears) with CI fittings based on subjective loudness scaling. Results A reference range for the oSRTs was defined that was identified in CI patients with eSRT-based fittings. Sound levels for stapedius reflex detection were inside the reference target range in 70% of the cases, below the reference range (i.e. down to 40 dB HL) in 20% of the cases, and above the reference range in 10% of the cases. Conclusion Stapedius reflex detection in a free sound field may help detect fittings with too high or too low stimulation levels that might reduce audiological performance.

Automated Adaptive Wideband Acoustic Stapedius Reflex Thresholds in Adults With Normal Hearing and Sensorineural Hearing Loss.

This study compared the measurement of the acoustic stapedius reflex threshold (ART) obtained using a traditional method with that obtained using an automated adaptive wideband (AAW) method. Participants included three groups of adults with normal hearing (NH), mild sensorineural hearing loss (SNHL), or moderate SNHL. The purpose of the study was to compare ARTs for the three groups and to determine which method had the best performance in detecting SNHL. Ipsilateral and contralateral ARTs were obtained using 0.5, 1, and 2 kHz tonal activators, and broadband noise (BBN) activators on a traditional admittance system (Clinical) at tympanometric peak pressures (TPP) and on an experimental wideband system using an AAW method at both ambient pressure and TPP. ART data previously reported for 39 NH adults with a mean age of 47.7 years were compared with data for 25 participants with mild SNHL with a mean age of 63.8 years, and 20 participants with moderate SNHL with a mean age of 65.7 years. Differences in ARTs between the normal-hearing and SNHL groups for the three methods were examined using a General Linear Model Repeated-Measures test. A receiver operating characteristic curve (ROC) analysis was also used to determine the ability of an ART test to detect SNHL. For the 0.5 kHz activator condition, there were no significant group mean differences in ART between NH and SNHL groups for either ipsilateral or contralateral activator presentation modes for the Clinical or AAW methods. There were significant group mean differences for the 1 and 2 kHz tonal activators and BBN activator for both ipsilateral and contralateral modes with greater differences in ART between groups for the AAW method than the Clinical method. In these conditions, the mean ART was lower for the AAW tests relative to the Clinical test. The greatest difference between groups was for the ipsilateral AAW tests for the comparison of NH with moderate SNHL for the BBN activator. This difference was approximately 20 dB for the AAW tests and 8 dB for the Clinical test. The ROC analysis showed that the area under the ROC curve (AUC) increased with the frequency of the activator stimulus and with the degree of hearing loss and was maximal for the BBN activator for both the AAW and Clinical methods for both ipsilateral and contralateral presentations. For ipsilateral and contralateral ART tests for activator frequencies above 0.5 kHz and BBN, listeners with SNHL generally had elevated ARTs compared with those with NH. The AAW method resulted in greater differences between SNHL groups and NH than the Clinical method. The AUC for detecting SNHL also increased with activator frequency and degree of hearing loss and was greatest for the BBN activator for the AAW method in both the ambient and TPP conditions. The results are encouraging for the use of an AAW ART method for the assessment of individuals with SNHL.

Accessing the stapedius muscle via novel surgical retrofacial approach during cochlear implantation surgery: Intraoperative results on feasibility and safety.

Human stapedius muscle (SM) can be directly and safely accessed via retrofacial approach, opening new approaches to directly measure the electrically evoked stapedius reflex threshold (eSRT). The measurement of the SM activity via direct surgical access represents a potential tool for objective eSRT fitting of cochlear implants (CI), increasing the benefit experienced by the CI users and leading to new perspectives in the development of smart implantable neurostimulators. 3D middle-ear reconstructions created after manual segmentation and related SM accessibility metrics were evaluated before the CI surgery for 16 candidates with assessed stapedius reflex. Retrofacial approach to access the SM was performed after facial recess exposure. In cases of poor exposition of SM, the access was performed anteriorly to the FN via drilling of the pyramidal eminence (PE). The total access rate of the SM via both the retrofacial and anterior approach of the FN was 100%. In 81.2% of cases (13/16), the retrofacial approach allowed to access the SM on previously categorized well exposed (8/8), partially exposed (4/5), and wholly concealed (1/3) SM with respect to FN. Following intraoperative evaluation in the remaining 18.8% (3/16), the SM was accessed anteriorly via drilling of the PE. Exposure of SM with respect to the FN and the sigmoid sinus's prominence was a predictor for the suitable surgical approach. The retrofacial approach offers feasible and reproducible access to the SM belly, opening direct access to electromyographic sensing of the eSRT. Surgical planner tools can quantitatively assist pre-surgical assessment.

Sinus tympani revisited for planning retrofacial approach—radiologic study in pneumatized temporal bones and its surgical implications

Background and purposeRetrofacial approach (RFA) is an access route to sinus tympani (ST) and it is used in cholesteatoma surgery, especially when type C ST is encountered. It may also be used to gain an access to stapedius muscle to assess the evoked stapedius reflex threshold. The primary object of this study was to evaluate the morphology of sinus tympani and its relationship to facial nerve (FN) and posterior semicircular canal (PSC) in context of planning retrofacial approach in pneumatized temporal bones.MethodsCBCT of 130 adults were reviewed. The type of sinus tympani was assessed according to Marchioni's classification. Width of entrance to sinus tympani (STW), depth of ST (STD), distance between the posterior semicircular canal and facial nerve (F-PSC), distance between the latter plane to the floor of ST at the right angle (P-ST) were measured at level of round window (RW) and pyramidal ridge (PR).ResultsAll of the bones were well-aerated and classified in Dexian Tan pneumatization group 3 or 4. Type B of ST is dominant (70.8%) in adult population with no history of inflammatory otologic diseases, followed by type C (22.7%) and then type A (6.5%). The depth of ST (STD) presented significant deviations (ANOVA, p < 0.05) among all three types. STW reaches greater values on the level of PR. F-PSC does not correlate with type of ST. In over 75% of examined type C sinus tympani the distance P-ST was less than 1 mm.ConclusionsThe qualitative classification of the sinus tympani into types A, B and C, introduced by Marchioni is justified by statistically significant differences of depth between individual types of tympanic sinuses. The STW distance reaches greater values inferiorly—it may suggest that RFA should be performed in infero-superior manner rather than opposite direction. Preoperative assessment of temporal bones CT scans gives very important information about size of sinus tympani and distance between FN and PSC.

Maximum acceptable level for the determination of ECAP and ESRT in a paediatric population

Objectives Two of the most used objective measures are electrically evoked action potentials (ECAPs) and electrically evoked stapedius reflex thresholds (ESRTs). Although stimuli used for these measures differ considerably, both measures are influenced by subjective loudness percept. We focus on the subjective maximum acceptable loudness (MAL) to investigate if loudness sensitivity varied along the electrode array during ECAP recordings. In addition, we explored how the MAL reached during an ECAP recording related to the postoperative ESRT. Methods Uni- and bilaterally implanted young CI users (n = 15, average age = 9 y, age range 3–18 y) underwent ECAP and ESR recordings using the clinical software MAESTRO (MED-EL, Innsbruck, Austria) and a commercially available immittance instrument (PATH MEDICAL GmbH, Germering, Germany). Results Loudness tolerance during ECAP recordings was lowest at the two apical-most electrode contacts (number 1 and 2). There was a moderate correlation between the MAL achieved during ECAP recordings and ESR maximum stimulation amplitudes. (r: 0.44344). Conclusions ECAP recordings should commence at basal or medial contacts to increase the users’ comfort and loudness tolerance, especially in young CI users. A higher maximum stimulation appears to increase the chance of the automatic determination of ECAP thresholds for all electrode contacts.

Outcome of Cochlear Implantation in Children with Auditory Neuropathy-A Dual Case Study

Objectives: The aim of this study is to compare the outcome of cochlear implantation in two pediatric auditory neuropathy cases. Methods: Two cases with auditory neuropathy were taken. Case 1 was 10 year old male. Case 2 was 11 year old male. In preoperative assessment both have bilateral severe to profound sensory-neural hearing loss. Case 1 was implanted by MED-EL using sonata Ti100 opus 2 processor. Case 2 was implanted using MED-EL using sonata Ti100 opus 2 processor. Both cases were given auditory verbal therapy. Both cases attended auditory verbal therapy for a period of 2 years. In postoperative assessment for each individual subject, electrically evoked compound action potentials (ECAPs), electrically evoked stapedius reflex threshold (ESRT), and electrically evoked auditory brainstem response (EABR) thresholds were determined. The following questionnaire extended receptive expressive emergent language scale (E-REELS) , Categories of Auditory Performance (CAP) score, Speech Intelligibility Rating (SIR) scale, Meaningful Auditory-Integration Scale (MAIS) and Meaningful Use of Speech Scale (MUSS) are scales were administered. Results: In the postoperative assessment, ECAP, ESRT, EABR, MUSS, MAIS shows that case 1 with auditory neuropathy have better performance than case 2. Conclusion: It is essential that all possible complications and postoperative performance should be considered in cochlear implantation for auditory neuropathy individuals

Normative eSRT Value among MED-EL Pediatric Population in Indonesia

Introduction: Early stimulation of the auditory sense is essential for the development of language and speech. In children with a cochlear implant, the most common issue is whether the hearing has been optimized or not, as they are still unable to provide reliable feedback regarding their hearing ability. Thus, electrically evoked stapedius reflex threshold (ESRT) based fitting has been used as one of the available methods in programming a cochlear implant (CI) audio processor. As eSRT is an objective test, patient cooperation was not needed making it especially beneficial for children with CI who have limitations in providing feedback. Now that eSRT has been applied commonly almost worldwide, the goal of this study is to determine the normative value of eSRT among the pediatric population in Indonesia. Methods: A total of 32 pediatric CI users in the age range 3 - 11 years implanted with Med-El cochlear implant were included in this study. ESRT was performed during follow-up mapping between September 2021 and January 2022 in the Med-El Indonesia hearing center. Results: The result of the present study showed an average normative value of 20.55 qus. This finding is consistent with the values obtained in previous studies. Conclusion: The result found can be used as a valuable indicator of average optimised MCL among the pediatric population.

Accessing the Stapedius Muscle Via Novel Surgical Retrofacial Approach: A Cadaveric Feasibility Study.

Despite the complete embodiment of the stapedius muscle (SM) into the pyramidal eminence, it is possible to safely gain access to the SM belly via a retrofacial approach. This presents a novel approach to directly measure the electrically evoked stapedius reflex threshold (eSRT). Objective fitting of maximum comfortable loudness levels for cochlear implant users can improve the benefit introduced by the device. Sensing SM activity via direct surgical access represents a potential tool for objective eSRT fitting. Eighteen human temporal bones (TBs) were used. Micro-computed tomography was performed for six TBs. Standard computed tomography for six TBs. Manual 3D-segmentation of the relevant middle and inner ear anatomy was performed on 12 TBs. Mastoidectomy and posterior tympanotomy allowed the access to middle ear of all 18 the TBs. Once identified the mastoidal segment of the facial nerve (FN), the retrofacial access to the SM was drilled. The total access rate was 72.2%. Only in the first three cases the posterior semi-circular canal was hit. The SM access was identified posterior to the FN at a 4 ± 0.78 mm distance from the stapes' head, almost halfway to the chorda tympani's branching point along the FN direction. The drilling depth to access the SM posterior to the external surface of FN on average was 2 ± 0.30 mm. The exposure took on average of 5 to 8 minutes. The retrofacial approach seems to offer a feasible and reproducible access to the SM belly opening an avenue to electromyographic sensing of eSRT.

The optimal probe tone frequency for eSRT measurements at individual electrodes in children with cochlear implants

Background Higher probe tone frequencies have been shown to increase the elicitation rates in electrically evoked stapedius reflex threshold (eSRT) measurements. Objectives To determine the optimal probe tone frequency for contralateral eSRT measurements at individual electrodes in children with unilateral cochlear implants and to assess the relationship between eSRTs for this frequency and most comfortable levels (M-levels). Materials and methods Contralateral eSRT measurements with three probe tone frequencies (226, 678, and 1000 Hz) at individual electrodes were performed on 26 paediatric Advanced Bionics cochlear implant recipients. Results The elicitation rates of eSRTs for 226, 678, and 1000 Hz probe tones were 73.08% (57/78), 88.46% (69/78), and 88.46% (69/78), respectively. The average eSRT for the 1000 Hz probe tone was significantly lower than those for 226 and 678 Hz probe tones (p<.001 and p=.009, respectively). ESRTs for the 1000 Hz probe tone and M-levels were significantly correlated at all tested electrodes (all p<.001). Conclusions and significance The optimal probe tone frequency for contralateral eSRT measurement at individual electrodes in children with unilateral cochlear implants is 1000 Hz. ESRTs for the 1000 Hz probe tone are significantly correlated with M-levels and can be used to guide the M-levels setting in these children.

Automated Adaptive Wideband Acoustic Reflex Threshold Estimation in Normal-hearing Adults.

Acoustic stapedius reflex threshold (ART) tests are included in a standard clinical acoustic immittance test battery as an objective cross-check with behavioral results and to help identify site of lesion. In traditional clinical test batteries, middle-ear admittance of a 226 Hz probe is estimated using ear-canal measurements in the presence of a reflex-activating stimulus. In the wideband (WB) acoustic immittance ART test used in this study, the pure-tone probe is replaced by a WB probe stimulus and changes in absorbed power are estimated using ear-canal measurements in the presence of the activator. The ART is defined as the lowest level at which a criterion change in admittance (clinical) or absorbed power (WB) is observed in the presence of the activator. In the present study, ARTs were obtained in adults with normal hearing using the clinical, manual method and with a new WB automated adaptive threshold detection method. It was hypothesized that the WB test would result in lower ARTs than the clinical test because reflex-related changes in power absorbance could be observed across multiple frequency bands in the WB test compared with a single frequency in the traditional test. Data were collected in a prospective research design. ARTs were obtained in ipsilateral and contralateral conditions using 500, 1000, 2000 Hz, and broadband noise (BBN) activators on a clinical system and on an experimental WB system. The bandwidth of the BBN activator was 125 to 4000 Hz on the clinical system and 200 to 8000 Hz on the wideband system. ARTs were estimated at both tympanometric peak pressure (TPP) and ambient pressure on the WB system. Data were collected in both ears of 39 adults (21 males) of mean age 47.7 years (range 23-72 years). Differences in ARTs among the three threshold estimation methods (clinical, WB at TPP, WB at ambient) were examined using the general linear model repeated measures test in SPSS. Post-hoc pairwise comparisons were completed with Bonferroni correction for multiple comparisons. Statistical significance was defined as p < 0.05 for all analyses. ARTs obtained on the WB system at TPP and ambient pressure were significantly lower than obtained on the clinical system. ARTs obtained on the WB system at TPP were significantly higher than at ambient pressure in the 500 and 2000 Hz ipsilateral conditions. WB automated adaptive ARTs in normal-hearing adults were lower than for clinical methods when measured at TPP and ambient pressure. Lower presentation levels required to estimate ART in the WB test may be more tolerable to patients. Patients with ARTs that are not present at the maximum level of a traditional reflex test may have present ARTs with a WB ART test, which may reduce the need to refer for additional testing for possible retrocochlear involvement. Automation of the test may allow clinicians more time to attend to the other requisite tasks of a hearing evaluation and make the system useful for telehealth applications.

Intraoperative recordings of electromyogenic responses from the human stapedius muscle

Following surgical implantation of a cochlear implant, the external processor must be programmed individually, which is typically achieved by behavioral measurements, with the user indicating the perceived loudness between the threshold and the maximum comfort levels (MCLs). However, the stapedius reflex measurement could be used instead, as the basis for programming the fitting maps. The electrically evoked stapedius reflex threshold is known to have a high correlation with the MCLs and thus is used as an objective tool to determine the MCL, especially in children and non-cooperative patients. Previous studies demonstrated that the electromyogenic (EMG) activity of the stapedius muscle could be measured to determine stapedius reflex responses. The objective of this study was to demonstrate that intraoperative EMG recordings from the stapedius muscle could be performed with an EMG recording electrode designed for chronical implantation.Ten adult subjects with single sided deafness (SSD) participated in this study. The study was split up into a pre-, intra- and postoperative phase. In the preoperative phase the subjects were screened for the presence of the acoustic stapedius reflex by using a standard tympanometer in the ear to be implanted, while the contralateral ear was stimulated acoustically. During the intraoperative phase an EMG recording electrode was placed in the stapedius muscle and EMG responses were recorded during acoustical and electrical stimulation. The surgical procedure consisted of two interconnected procedures: A classical surgical approach for cochlear implantation with two additional surgical steps, and the temporary placement of an EMG recording electrode in the stapedius muscle made through an opening in the pyramidal eminence, allowing EMG recordings. The postoperative phase was used to evaluate the preservation of the stapedius reflex postoperatively at 1- and 6-months with contralateral acoustic and ipsilateral electrical stimulation.The EMG recording electrode could successfully be placed in the stapedius muscle in all subjects and was able to reliably record EMG signals from the stapedius muscle elicited by acoustic and electrical stimulation. Overall, EMG recordings were obtained intraoperatively in all subjects tested (8 out of 8 subjects). Contralateral acoustic stapedius reflexes were obtained in 6 out of 8 subjects and ipsilateral electrical stapedius reflex in 7 out of 8 subjects. In the postoperative phase, the preservation of the postoperative reflex was observed in 6 out of 10 subjects 1-month after surgery and in 8 out of 10 subjects 6-months after surgery.The study showed that intraoperative EMG recordings from the stapedius muscle can be performed with an EMG recording electrode designed for chronical implantation. The minimally invasive procedure is promising; in particular with regard to the future perspective of measurements in the long-term with an integrated closed-loop self-fitting system.

Effect of Number of Electrodes Used to Elicit Electrical Stapedius Reflex Thresholds in Cochlear Implants

Introduction: When mapping cochlear implant (CI) patients with limited reporting abilities, the lowest electrical stimulus level that produces a stapedial reflex (i.e., the electrical stapedius reflex threshold [eSRT]) can be measured to estimate the upper bound of stimulation on individual or a subset of CI electrodes. However, eSRTs measured for individual electrodes or a subset of electrodes cannot be used to predict the global adjustment of electrical stimulation levels needed to achieve comfortable loudness sensations that can be readily used in a speech coding strategy. In the present study, eSRTs were measured for 1-, 4-, and 15-electrode stimulation to (1) determine changes in eSRT levels as a function of the electrode stimulation mode and (2) determine which stimulation mode eSRT levels best approximate comfortable loudness levels from patients’ clinical maps. Methods: eSRTs were measured with the 3 different electrical stimulation configurations in 9 CI patients and compared with behaviorally measured, comfortable loudness levels or M-levels from patients’ clinical maps. Results: A linear, mixed-effects, repeated-measures analysis revealed significant differences (p < 0.01) between eSRTs measured as a function of the stimulation mode. No significant differences (p = 0.059) were measured between 15-electrode eSRTs and M-levels from patients’ clinical maps. The eSRTs measured for 1- and 4-electrode stimulation differed significantly (p < 0.05) from the M-levels on the corresponding electrodes from the patients’ clinical map. Conclusion: eSRT profiles based on 1- or 4-electrode stimulation can be used to determine comfortable loudness level on either individual or a subset of electrodes, and 15-electrode eSRT profiles can be used to determine the upper bound of electrical stimulation that can be used in a speech coding strategy.

Stapedius reflex evoked in free sound field in cochlear implant users compared to normal-hearing listeners

Objective To determine the relation between stapedius reflex thresholds in cochlear implant users evoked once through direct electric stimulation on single channels (ESRT) and once through acoustic stimulation in free sound field. For comparison, stapedius reflex thresholds were obtained in free sound field in a normal-hearing control group. Design For each participant a new ESRT-based fitting was created. Stapedius reflex thresholds were obtained for this new fitting in free sound field for different loudness adjustments. Acoustic stimuli for eliciting the stapedius reflex were narrow band noise signals covering the audiometric frequency range. Study sample N = 29 experienced CI users (34 ears) and N = 10 normal hearing listeners. Results ESRT-based fitting resulted in different stapedius reflex behaviour compared to normal-hearing listeners. A frequency dependence was observed. Stapedius reflex thresholds decreased with increasing centre frequencies of acoustic narrow band noise stimuli. A linear relation between upper stimulation levels on the implant channels and corresponding stapedius reflex thresholds evoked in free sound field was found. Conclusion The found correlation may be a guideline for adjusting the electrical dynamic range during cochlear implant fitting. This allows the implant system to mimic the natural reflex behaviour in the best possible way and potentially avoid overstimulation.

Examination of the use of electrical stapedius reflex thresholds in attaining upper stimulation levels in cochlear implant mapping in children: A systematic review

Examination of the use of electrical stapedius reflex thresholds in attaining upper stimulation levels in cochlear implant mapping in children: A systematic review

Endoscopic measurement of the stapedius reflex threshold

【背景】強大音から蝸牛を防御するアブミ骨筋反射（SR）は，音刺激が閾値を超えると両側の顔面神経核が刺激され両側性に生じる．検査としてはインピーダンスオージオメトリーによるレフレックス検査があるが，アブミ骨筋が収縮してアブミ骨の可動が耳小骨やMI joint を逆行に経由して鼓膜まで可動したものを間接的に検出しているにすぎない．そのため，真の閾値は測定できておらず，実際はさらに小さな音刺激でもSRが生じているはずである．SR を直接観察することができれば，より正確な閾値を評価することができるはずである． 【目的】正確なSR 閾値を測定する方法の開発 【対象と方法】健側耳聴力が正常かつ患側の鼓室に病変を伴わない，局所麻酔下に内視鏡下耳科手術を施行する患者を対象とする．術中に健側耳への音刺激にて対側耳に生じるSRを内視鏡下にアブミ骨の可動を直接確認し閾値の測定を行う．また，鼓室に銀ボール電極を設置し，筋電図を測定することにより，電気生理学的にも閾値を評価する． 【結果】内視鏡下にSRを直接確認することができた．術前のレフレックス検査によるSR閾値と比べて，内視鏡下で観察した最小音刺激閾値は低かった．アブミ骨筋筋電図も測定することができ，内視鏡下に観察した閾値とほぼ同じであった． 【考察】この検討結果はSRのより正確な閾値を測定する方法の開発に寄与する．本検討の臨床応用として，末梢性顔面神経麻痺の超早期予後診断への活用が挙げられる．SRが検出されれば顔面神経麻痺は回復しやすいとされているが，検出されなくても麻痺が回復することも多く，レフレックス検査では正確な予後診断に限界がある．それは，SRの真の閾値を測定できていないことが関係しており，より正確な閾値を測定できれば，予後診断の精度も向上するはずである．今後更なる検討を行っていく．

Effect of Electrode to Modiolus Distance on Electrophysiological and Psychophysical Parameters in CI Patients With Perimodiolar and Lateral Electrode Arrays.

To investigate the intracochlear position of the latest Cochlear Nucleus 532 electrode array compared with the straight Nucleus 522 and the precurved 512 arrays and determine the effect of the electrode-modiolus distance on electrically evoked compound action potential, C-levels, electrically evoked stapedius reflex thresholds (ESRTs), and impedances. Postoperative high-resolution cone beam computational tomography images of 30 patients with Cochlear Nucleus 532, 522, and 512 implants were evaluated using the Comet (Cochlea Measurement Tool) program to determine the distance between the 22 individual electrode contacts and the medial wall. ESRTs were documented intraoperatively and electrophysiological as well as psychophysical parameters were measured at multiple time points including the first fitting after the initial activation. The electrode-modiolus distance in perimodiolar arrays is uniformly small across the array, whereas in a straight electrode carrier it varies significantly along the length of the array. Electrically evoked compound action potential thresholds and C-levels are larger with increased distance to the modiolus. Impedances and stapedius reflex thresholds do not differ significantly between the arrays. Our results show that the electrode position has a significant effect on both electrophysiological and psychophysical parameters, while impedances and ESRTs are not impacted. Novel tools can be used in the evaluation of high resolution cone beam computational tomography images to determine individual electrode-modiolus distances after cochlear implantation. The results of this study suggest that the correlations between electrode-modiolus distance and electrophysiological and psychophysical parameters are not sufficiently strong to adjust CI-fitting based on imaging data.

Comparison of Perimodiolar Electrodes: Imaging and Electrophysiological Outcomes.

The perimodiolar CI532 Slim Modiolar electrode has been designed to bring the electrode contacts close to auditory nerve while reducing cochlear trauma during its insertion. It is currently unknown to what extent the electrode position and electrophysiological outcomes of the Slim Modiolar electrode differ from other perimodiolar electrodes. The objective was to compare the electrode position and electrophysiological outcomes between the CI532 Slim Modiolar and CI512 Contour Advance electrode. Forty-six adult patients received a Slim Modiolar or Contour Advance electrode. Electrode types were compared using intraoperative electrode impedances, evoked compound action potential (ECAP) and stapedius reflex thresholds, as well as position parameters from postoperative computed tomography or digital volume tomography images (medial-lateral position, electrode-to-modiolus distance, insertion angle). The medial-lateral position indicates a closer modiolar placement of the Slim Modiolar compared with the Contour Advance. Individual electrode contact measurements, however, showed significantly larger electrode-to-modiolus distances and higher ECAP thresholds for the Slim Modiolar in the basal region. On contacts E20-22 the Slim Modiolar is slightly closer to the modiolus compared with the Contour Advance, but this did not result in lower ECAP thresholds. Perimodiolar electrodes can vary in their intracochlear position, leading to divergent electrophysiological outcomes. To detect these differences, investigations must be done for each electrode contact rather than using a global factor for the whole electrode array. While the electrode dislocation rate is lower with the Slim Modiolar than with the Contour Advance, electrode-to-modiolus proximity is smaller and ECAP thresholds are lower with the Contour Advance in the basal cochlear region.

The Relationship between Electrical Stapedius Reflex Thresholds and Behaviorally Most Comfortable Levels in Experienced Cochlear Implant Users.

Programming the cochlear implant's speech processor with subjective methods in young, uncooperative children is difficult. Since young children cannot provide adequate feedback to the clinician, objective methods which do not require patient's response were often used. Electrical Stapedius Reflex Test is one of the most common procedures used. The goal of this study was to investigate the relationship between electricalstapedius reflex thresholds and behaviorally most comfortable levels in experienced cochlear implant users. The patients implanted with two brands of cochlear implants were compared in terms of electrical stapedius reflex thresholds versus most comfortable levels. Speech tests results were also compared between the two groups. 46 cochlear implanted patients who had at least 1 year of cochlear implant experience were included in the study. 28 patients were implanted with Nucleus, 18 patients with Med-El devices. Moderate correlations were obtained between Electrical Stapedius Reflex (ESR) thresholds and C levels in Nucleus users; higher correlations were obtained for Med-El patients. ESR thresholds were present at higher levels than MCL/C levels in both Nucleus and Med-El users. No significant difference was obtained between the two groups in terms of speech tests. ESR test can be very informative for programming young and uncooperative patients.