Normative Wideband Reflectance, Equivalent Admittance at the Tympanic Membrane, and Acoustic Stapedius Reflex Threshold in Adults.

OBJECTIVES: Wideband acoustic immittance (WAI) measures such as pressure reflectance, parameterized by absorbance and group delay, equivalent admittance at the tympanic membrane (TM), and acoustic stapedius reflex threshold (ASRT) describe middle ear function across a wide frequency range, compared with traditional tests employing a single frequency. The objective of this study was to obtain normative data using these tests for a group of normal-hearing adults and investigate test-retest reliability using a longitudinal design. DESIGN: A longitudinal prospective design was used to obtain normative test and retest data on clinical and WAI measures. Subjects were 13 males and 20 females (mean age = 26 years). Inclusion criteria included normal audiometry and clinical immittance. Subjects were tested on two separate visits approximately 1 month apart. Reflectance and equivalent admittance at the TM were measured from 0.25 to 8.0 kHz under three conditions: at ambient pressure in the ear canal and with pressure sweeps from positive to negative pressure (downswept) and negative to positive pressure (upswept). Equivalent admittance at the TM was calculated using admittance measurements at the probe tip that were adjusted using a model of sound transmission in the ear canal and acoustic estimates of ear-canal area and length. Wideband ASRTs were measured at tympanometric peak pressure (TPP) derived from the average TPP of downswept and upswept tympanograms. Descriptive statistics were obtained for all WAI responses, and wideband and clinical ASRTs were compared. RESULTS: Mean absorbance at ambient pressure and TPP demonstrated a broad band-pass pattern typical of previous studies. Test-retest differences were lower for absorbance at TPP for the downswept method compared with ambient pressure at frequencies between 1.0 and 1.26 kHz. Mean tympanometric peak-to-tail differences for absorbance were greatest around 1.0 to 2.0 kHz and similar for positive and negative tails. Mean group delay at ambient pressure and at TPP were greatest between 0.32 and 0.6 kHz at 200 to 300 µsec, reduced at frequencies between 0.8 and 1.5 kHz, and increased above 1.5 kHz to around 150 µsec. Mean equivalent admittance at the TM had a lower level for the ambient method than at TPP for both sweep directions below 1.2 kHz, but the difference between methods was only statistically significant for the comparison between the ambient method and TPP for the upswept tympanogram. Mean equivalent admittance phase was positive at all frequencies. Test-retest reliability of the equivalent admittance level ranged from 1 to 3 dB at frequencies below 1.0 kHz, but increased to 8 to 9 dB at higher frequencies. The mean wideband ASRT for an ipsilateral broadband noise activator was 12 dB lower than the clinical ASRT, but had poorer reliability. CONCLUSIONS: Normative data for the WAI test battery revealed minor differences for results at ambient pressure compared with tympanometric methods at TPP for reflectance, group delay, and equivalent admittance level at the TM for subjects with middle ear pressure within ±100 daPa. Test-retest reliability was better for absorbance at TPP for the downswept tympanogram compared with ambient pressure at frequencies around 1.0 kHz. Large peak-to-tail differences in absorbance combined with good reliability at frequencies between about 0.7 and 3.0 kHz suggest that this may be a sensitive frequency range for interpreting absorbance at TPP. The mean wideband ipsilateral ASRT was lower than the clinical ASRT, consistent with previous studies. Results are promising for the use of a wideband test battery to evaluate middle ear function.

On the origin of ear clicks during deglutition or pressure equalization.

To explore the origin of clicking sounds in the ear during deglutition or other pharyngeal movements, which are interpreted differently in the literature. Experimental study at a tertiary referral centre. Acoustic phenomena during a forced opening test of the Eustachian tube (ET) were studied in a temporal bone model. Additionally, in vivo experiments were carried out in healthy volunteers for ruling out movements of the ossicular chain or the drumhead as potential causes of clicks. Thus, acoustic recordings were performed parallel to stapedius or tensor reflex measurements or pneumatic video endoscopies of the tympanic membrane. Obviously the acoustic signals (clicks) appear when the tube opens, which could be visualized and acoustically recorded during forced opening tests in temporal bone experiments. Middle ear muscle contractions with movements of the tympanic membrane did not cause any click events. Together with the results of a previous paper (9) we interpret the clicks as disruptions of fluid or mucus films covering the mucosa during the ET opening. The final goal of our studies is to use such clicks as indicators of ET openings in a new tube function test, which has to be elaborated.

Increased contralateral suppression of otoacoustic emissions indicates a hyperresponsive medial olivocochlear system in humans with tinnitus and hyperacusis.

Atypical medial olivocochlear (MOC) feedback from brain stem to cochlea has been proposed to play a role in tinnitus, but even well-constructed tests of this idea have yielded inconsistent results. In the present study, it was hypothesized that low sound tolerance (mild to moderate hyperacusis), which can accompany tinnitus or occur on its own, might contribute to the inconsistency. Sound-level tolerance (SLT) was assessed in subjects (all men) with clinically normal or near-normal thresholds to form threshold-, age-, and sex-matched groups: 1) no tinnitus/high SLT, 2) no tinnitus/low SLT, 3) tinnitus/high SLT, and 4) tinnitus/low SLT. MOC function was measured from the ear canal as the change in magnitude of distortion-product otoacoustic emissions (DPOAE) elicited by broadband noise presented to the contralateral ear. The noise reduced DPOAE magnitude in all groups ("contralateral suppression"), but significantly more reduction occurred in groups with tinnitus and/or low SLT, indicating hyperresponsiveness of the MOC system compared with the group with no tinnitus/high SLT. The results suggest hyperresponsiveness of the interneurons of the MOC system residing in the cochlear nucleus and/or MOC neurons themselves. The present data, combined with previous human and animal data, indicate that neural pathways involving every major division of the cochlear nucleus manifest hyperactivity and/or hyperresponsiveness in tinnitus and/or low SLT. The overactivation may develop in each pathway separately. However, a more parsimonious hypothesis is that top-down neuromodulation is the driving force behind ubiquitous overactivation of the auditory brain stem and may correspond to attentional spotlighting on the auditory domain in tinnitus and hyperacusis.

Unilateral cochlear implant use promotes normal-like loudness perception in adolescents with childhood deafness.

OBJECTIVES: Behavioral measures of cochlear implant (CI) device stimulation levels can be difficult to obtain in individuals with limited or no hearing experience. Loudness measures are particularly challenging. It would therefore be useful to have a battery of objective and behavioral measures to determine CI stimulation levels in listeners with childhood deafness. In the present study, the authors characterized loudness growth in 20 adolescents: 8 with normal hearing and 12 CI participants with pre/perilingual bilateral sensorineural hearing loss. They asked (1) do adolescent CI users with childhood deafness experience similar increases in loudness as their peers with normal hearing? and (2) can loudness be predicted by objective measures of auditory activity? The authors hypothesized that loudness perception would be significantly different between CI and normal-hearing groups and that it would correlate with objective measures. DESIGN: CI users were recruited from the Cochlear Implant Program at The Hospital for Sick Children and all had used unilateral Nucleus CIs for at least 2 years. The dynamic range for each participant was defined as the difference between the behavioral threshold and the electrically evoked stapedius reflex (ESR) threshold. Loudness growth was assessed within this range behaviorally on a continuous visual scale and objectively with physiological measures. Auditory brainstem responses (ABRs) and ESRs were recorded in both groups and electrically evoked compound action potentials (ECAPs) of the auditory nerve were recorded in addition in CI listeners. The regression line slopes of ECAP and ABR amplitude growth functions were then calculated and compared with behavioral loudness growth slopes in the upper portion (40-100%) and lower portion (0-40%) of the dynamic range. Electrical pulse stimuli (in CI users) and acoustic clicks (in normal-hearing participants) were presented within each participant's dynamic range. RESULTS: The mean dynamic range in CI listeners was more variable than in normal-hearing individuals. Despite this difference, loudness at the ESR threshold was not significantly different in CI adolescents from their normal-hearing peers, and CI users exhibited normal-like loudness growth. There was a significantly positive correlation between ECAP amplitude growth and loudness growth in CI users in the upper portion of the dynamic range, while ABR wave V amplitude growth was not related to loudness growth in either group. CONCLUSIONS: We confirmed that the ESR threshold is a good measure of comfortably loud levels in adolescents with cochlear implants and their normal-hearing peers. Adolescents using CIs show normal-like rates of loudness growth on average, despite having highly variable dynamic ranges of hearing. Individual rates of loudness growth in the upper dynamic range in CI users can be predicted by the rate of amplitude growth of the ECAP. Thus, the rate of neural recruitment with increasing CI current is important for loudness perception in pre/perilingually deaf listeners and should be considered when programming their CIs.

Would an endosteal CI-electrode make sense? Comparison of the auditory nerve excitability from different stimulation sites using ESRT measurements and mathematical models.

UNLABELLED: Regarding potential endosteal cochlear implant electrodes, the primary goal of this paper is to compare different intra- and extra-cochlear stimulation sites in terms of current strengths needed for stimulating the auditory nerve. Our study was performed during routine cochlear implantation using needle electrodes for electric stimulation and by visually recording electrically elicited stapedius reflexes (ESRT) as a measure for the stimulus transfer. Of course this rather simple setup only allows rough estimations, which, however, may provide further arguments whether or not to proceed with the concept of an endosteal electrode. In addition, a mathematical model is being developed. In a pilot study, intra-operative electric stimuli were applied via a needle electrode commonly used for the promontory stimulation test. Thus, stapedius reflex thresholds (ESRTs), electrically elicited via the needle from different points inside and outside the cochlea served as indicators for the suitability of different electrode positions towards the modiolus. Tests were performed on 11 CI-recipients. In addition, the extension of electrical fields from different stimulation sites is simulated in a mathematical cochlea model. In most patients ESRT measurements could be performed and evaluated. Thus an "endosteal" stimulation seems possible, although the current intensities must be higher than at intraluminal stimulation sites. Moreover, our model calculations confirm that the extension of electric fields is less favourable with increasing distance from the electrode to the ganglion nerve cells. In terms of hearing, the concept of an endosteal electrode should only be promoted, if its superiority for hearing preservation can be proven, e.g. in animal experiments. However, for other indications like the electric suppression of tinnitus, further research seems advisable. LEVELS OF EVIDENCE: N/A.

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.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Acoustic stapedius reflex function in man revisited.

OBJECTIVE: The objective of this study was to examine the role of the acoustic stapedius reflex in the protection of speech recognition from the upward spread of masking arising from low-frequency background noise. DESIGN: Speech recognition scores were measured for nine control participants (19-34 years) and six patients with transected stapedius tendons poststapedotomy (39-57 years) as a function of the amplitude of a low-frequency masker, presented at nominal signal to noise ratios of +5 dB, -5 dB, and -15 dB. All participants had pure-tone hearing thresholds in the normal range. Continuous high-pass noise was present in all conditions to avoid ceiling effects; this reduced performance in quiet to approximately 85% for all participants. Scores were measured for soft and loud nonsense syllables (average third octave band levels of 35 and 65 dB SPL), so that a comparison of the low-frequency noise masking functions at the two levels would provide information about the effects of the reflex on speech intelligibility in noise. A third group of nine control participants (19-22 years) listened in the presence of a low-frequency masker gated to come on 1 sec before stimulus onset, to reduce the likelihood of reflex adaptation. The Speech-Intelligibility Index was used to quantify the amount of speech information available in each condition. RESULTS: Patients with transected tendons performed more poorly than control participants as a function of Speech-Intelligibility Index in all conditions, even at levels that were too soft for reflex activation. This could be because of postsurgical differences in sensitivity, the more advanced age of poststapedotomy group, or differences in medial olivocochlear inhibition. For loud speech, patient performance fell nearly linearly with increases in the low-frequency masker, but control participants' performance declined little as the signal to noise ratio declined from +5 to -5 dB, and then fell rapidly as the ratio declined to -15 dB. This plateau in the masking function did not occur for the patients. Masking functions obtained with the gated low-frequency masker were either highly similar or poorer to those obtained with a continuous masker, suggesting that the use of a continuous low frequency masker did not result in significant reflex adaptation. CONCLUSIONS: The stapedius reflex appears to offer some protection from the upward spread of masking of speech by background low-frequency noise at moderate levels, but not at high levels.

[The objective method for recording stapedial reflex during surgery for cochlear implantation].

The purpose of the present study was to develop a method for the objective registration of the stapedial reflex at the contralateral ear during cochlear implantation surgery on the affected one. The excessive pressure in the middle ear (up to 500 daPa) was compensated by the administration of an additional air volume (1 liter) into the AA220 impedance meter pneumatic circuit. A syringe was used to measure variations of pressure in the new pneumatic circuit. Eight of the 12 patients demonstrated coincident visual and objective reflex thresholds. In the remaining 4 patients, the visually apparent stapedial reflex thresholds proved higher than those obtained objectively by the standard procedure of impedancemetry. It is concluded that the objective registration of the stapedial reflex excludes the effect of subjective factors interfering with its estimation and provides the possibility for comparative intra- and postoperative studies using one and the same instrument.

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.

Evoked stapedius reflex and compound action potential thresholds versus most comfortable loudness level: assessment of their relation for charge-based fitting strategies in implant users.

AIM: The main goal of the present study was to assess the feasibility of using evoked stapedius reflex (eSR) and evoked compound action potential (eCAP) thresholds to create speech processor programs for children using Med-El Maestro software. The secondary goals were (1) to compare the eSR and eCAP thresholds recorded using charge units in experienced adults fitted with Med-El Pulsar CI100 cochlear implants with most comfortable loudness levels (MCLs) obtained for the apical, medial and basal electrodes, and (2) to compare eSR and eCAP thresholds for the apical, medial and basal electrodes between adults and children. METHODS: Fourteen children and 16 adults participated in the study. eSR and eCAP thresholds were measured in both groups using the auditory nerve response telemetry algorithm, with MCL being behaviourally measured only in the adult group. RESULTS: In the adult population, the correlation between eSR threshold and MCL was better for apical, medial and basal electrodes than that between eCAP threshold and MCL. There was no significant difference in the means obtained for eCAP and eSR thresholds in children and adults for any of the electrodes tested. This finding suggests that in children, the correlations between eCAP thresholds and MCL values, and those between eSR thresholds and MCL values are not lower than those generally found in adults. CONCLUSIONS: Although the eSR threshold is a better predictor of MCL values, both eSR and eCAP thresholds can be useful tools for assisting with map creation for children.

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

OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: ESR test can be very informative for programming young and uncooperative patients.

Test-retest reliability of the acoustic stapedial reflex test in healthy neonates.

OBJECTIVE: The acoustic stapedial reflex (ASR) test has been shown to provide useful information about the function of the auditory system. However, the reliability of this test when applied to healthy neonates has not been systematically studied. This study aimed to evaluate the test-retest reliability of the ASR test in newborn babies shortly after birth. DESIGN: Using a cross-sectional design, 219 healthy neonates, aged between 24 and 192 hr, who passed an automated auditory brain stem response screening test, were recruited and assessed using transient-evoked otoacoustic emissions (TEOAEs), high-frequency (1000 Hz) tympanometry, and ASR tests. One randomly selected ear from each neonate was tested. ASRs were elicited by presenting a 2 kHz pure tone and broadband noise (BBN) separately to the test ear in an ipsilateral stimulation mode using a Madsen Otoflex diagnostic immittance meter. A total of 194 (86/108 males/females; 115/79 left/right) ears, which met a set of inclusion criteria, were included in the test-retest reliability analysis for the 2-kHz tone stimulus. In addition, 123 (62/61 males/females; 77/46 left/right) ears were included in the test-retest reliability analysis for the BBN stimulus. The ASR threshold (ASRT) for each stimulus was measured. The ASR procedure was then repeated to acquire retest data. RESULTS: Ipsilateral ASRs were elicited in 91.3% (200/219) of neonates, whereas the remaining 8.7% (19/219) exhibited flat tympanograms (no identifiable peak) and absent reflexes with a "refer" outcome in the TEOAE test. The mean ASRT (76.2 dB HL averaged over 194 ears) for the 2 kHz pure tone was higher than that for the BBN (64.9 dB HL averaged over 123 ears). The findings, based on the results of an analysis of variance with repeated measure, showed that the ASRTs for the retest condition did not differ significantly from those of the first test for both stimuli (p > 0.05). The ASR test also showed high test-retest reliability as demonstrated by intracorrelation coefficients across the test-retest conditions of 0.83 for the 2 kHz pure tone and 0.76 for the BBN stimulus. CONCLUSION: This study demonstrated that ASRs could be consistently elicited from healthy neonates who showed a single-peaked configuration in the high-frequency tympanometry test and passed the automated auditory brain stem response and TEOAE tests. The findings showed that the ASRTs did not vary significantly across the test-retest conditions, and the high intracorrelation coefficients illustrate the reliability of the ASR test. Given the high test-retest reliability, the ASR test holds promise as a useful diagnostic/screening instrument in ascertaining the hearing status in neonates.

[Study of the relationship of stapedial reflex thresholds induced during cochlear implant surgery and the highest hearing comfort of paediatric patients]. / Estudio de la correlación entre los umbrales del reflejo estapedial inducido durante la cirugía del implante coclear y la máxima comodidad auditiva del paciente pediátrico.

INTRODUCTION AND GOALS: We have studied the relationship between the minimum stapedial reflex thresholds induced by means of the intra-operative stimulation of the cochlear implant and the post-operative thresholds of highest auditory comfort level. METHODS: We have assessed the maximum auditory comfort at the end of the first and second quarters following activation of the cochlear implant, by which time the strategy for codification of the stimuli and the programming map are considered to be already stable. The study was carried out at our cochlear implants unit. All the patients in the study had bilateral sensorineural deafness of varying aetiology and, following our standardized battery of diagnostic tests, were considered to be good candidates for cochlear implant. All aspects of the surgical technique were kept the same in order to be able to compare the results better. All members of the study were fitted with at least one Nucleus Freedom implant with Contour Advance Electrode. RESULTS: This study has been carried out on 24 cochlear implants placed in 22 patients younger than 14 years old. CONCLUSIONS: After assessing our experience, we can conclude that, in the Nucleus Freedom with Contour Advance Electrode cochlear implant, there is a positive statistical relationship between the levels of acoustic reflex induction obtained at the peri-operative stage and the levels of maximum auditory comfort, as determined by behavioural observation techniques for each of the different electrodes, in children up to 14 years old.

Multi-electrode sequential versus single electrode stimulation to elicit the stapedial reflex during cochlear implantation: Correlation with maximum comfort level.

OBJECTIVES: To assess whether electrical stimulation sequentially delivered through 4 electrodes located in different cochlear areas may elicit the stapedial reflex at lower levels compared to single electrode stimulation and to correlate the sequentially obtained values with the maximum comfort level (C-level). PATIENTS AND METHODS: A retrospective study was performed on 35 post-verbal adult patients (age 19-80 years) consecutively implanted in 2 cochlear implant centers, evaluating the level of stimulation (pulse width) necessary to electrically evoke the stapedial reflex with two different stimulation modalities: single electrode versus sequential 4 electrode stimulation. Threshold values were compared with C-level obtained at activation. RESULTS: The average differences of pulse width and C-level were significantly smaller (P<0.0001) when the stapedial reflex was obtained with the sequential stimulation modality and reached statistical significance for every single electrode (P<0.0001). CONCLUSIONS: Stapedial reflex thresholds obtained with sequential stimulation through 4 different electrodes significantly correlate to the C-level obtained at the first setting and may be helpful in defining the upper limit of the dynamic field during initial CI mapping.

Motoneurons of the stapedius muscle in the guinea pig middle ear: afferent and efferent transmitters.

The objective of the present study was to identify efferent and afferent transmitters of motoneurons of the stapedius muscle of the middle ear in order to gain more insight into the neuronal regulation of the muscle. To identify motoneurons, we injected the fluorescent neuronal tracer Fluorogold (FG) into the muscle after preparation of the middle ear in adult guinea pigs. Upon terminal uptake and retrograde neuronal transport, we observed FG in neurons located medial and ventral to the nucleus of the facial nerve ipsilateral to the injection site. Immunohistochemical studies of these motoneurons showed that the majority contains calcitonin gene-related peptide. Our data further demonstrate close spatial relationships of motoneurons to structures immunoreactive to either serotonin, substance P or neuronal nitric oxide and reveal that these neurons are under neuropeptidergic and nitrergic influence.

The effect of the 226-Hz probe level on contralateral acoustic stapedius reflex thresholds.

PURPOSE: The purpose of this study was to examine the effect of the 226-Hz probe level on the acoustic stapedius reflex threshold. METHOD: Contralateral reflex thresholds for a 1000-Hz pure-tone stimulus were obtained from 40 young adults with normal hearing using an experimental system at four 226-Hz probe levels (70, 75, 80, and 85 dB SPL) with a repeated measures experimental design. RESULTS: A repeated measures analysis of variance revealed that as the probe level increased over this 15-dB range, there was a mean decrease in reflex threshold of 2.5 dB SPL (p < .001), with the largest decrease for an individual participant of 12 dB. CONCLUSION: The results suggest that the level of the 226-Hz probe tone as used in clinical reflex measurements and as specified in the American National Standards Institute (1987) standard is sufficiently high to affect the acoustic reflex by facilitating its activation. The effect is small, on average, but may be of clinical significance for some individuals.

Acoustic stapedial reflex in normal adults: biological behavior and determination of threshold levels.

OBJECTIVE: To record acoustic reflex thresholds for admittance (Y) and its components, susceptance (B) and conductance (G) in healthy subjects and to establish normative data. STUDY DESIGN: Acoustic reflex threshold was determined in 100 healthy persons, divided into 5 age groups of 20 persons each (20-29, 30-39, 40-49, 50-59 and 60-69 years old). Detection was performed for Y, B, and G at 226-, 678- and 1,000-Hz probe tones, using 500-, 1,000-, 2,000- and 4,000-Hz stimuli. RESULTS: Statistically significant differences in acoustic reflex thresholds were revealed between different components, stimuli and tones. The lowest threshold level was recorded for Y at 226 Hz using stimulus 1,000 Hz. Four percent missing values were observed at 226 Hz. Subjects belonging to different age groups had different reflex thresholds. CONCLUSION: Inclusion of acoustic reflex detection for B and G offers more detailed information about the middle ear status compared with Y alone, and appears to be sensitive in detecting subtle diseases.

An Objective Method to Determine the Electrically Evoked Stapedius Reflex Threshold During Cochlea Implantation.

OBJECTIVE: In cochlea implantation, assessment of the electrically evoked stapedius reflex threshold (eSRT) provides information for postoperative adjustment of the speech processor. This is used to prevent undesired overstimulation. To this day, the reflex is visually identified by the surgeon. However, this method may be prone to error due to ventilation-associated situs excursions, blinking, or other distractions. Therefore, the aim of this study was to establish an objective and automatized method to determine the eSRT. METHODS: Video material documenting the intraoperative measurements was analyzed offline applying a tracking software to quantify stapes head movements. Moreover, a computer program (TrackerAnalyzer) was developed to detect reflex associated movements automatically. RESULTS: Reflex responses seen visually by the surgeon compared with visual registration on the video material postoperatively and to results of the automatized method with TrackerAnalyzer showed a high inter-rater agreement (Cohen's kappa coefficient = 0.47-0.59). 82% of events in which the TrackerAnalyzer registered reflexes that were not seen by the surgeon had values close but lower to the intraoperatively determined eSRT (mean -1.02 current units). CONCLUSION: We demonstrated the feasibility of an objective and automatized method to determine electrically evoked stapedius reflex thresholds in cochlea implantation.

Measurement of the Electrically Evoked Stapedial Reflex Response with Wideband Acoustic Reflectance Measurement.

BACKGROUND: The electrically evoked stapedial reflex threshold (ESRT) has been shown to be a good predictor of upper stimulation level for cochlear implant recipients. Previous research has shown that the ESRT may be recorded at lower stimulation levels and with a higher incidence of success with the use of higher frequency probe tones (e.g., 678 and 1000 Hz) relative to the use of the conventional 226-Hz probe tone. Research has also shown that the acoustic reflex may be recorded at lower stimulus levels with the use of wideband reflectance when compared to the acoustic reflex threshold recorded with a conventional acoustic immittance measurement. PURPOSE: The objective of this study was to compare the ESRT recorded with acoustic immittance and wideband reflectance measurements. RESEARCH DESIGN: A repeated measures design was used to evaluate potential differences in ESRTs with stimulation at an apical, middle, and basal electrode contact with the use of two different techniques, acoustic immittance measurement and wideband reflectance. STUDY SAMPLE: Twelve users of Cochlear Nucleus cochlear implants were included in the study. DATA COLLECTION AND ANALYSIS: Participants' ESRTs were evaluated in response to simulation at three different electrode contact sites (i.e., an apical, middle, and basal electrode contact) with the use of two different middle ear measurement techniques, acoustic immittance with the use of a 226-Hz probe tone and wideband reflectance with the use of a chirp stimulus. RESULTS: The mean ESRT recorded with wideband reflectance measurement was significantly lower when compared to the ESRT recorded with acoustic immittance. For one participant, the ESRT was not recorded with acoustic immittance before reaching the participant's loudness discomfort threshold, but it was successfully recorded with the use of wideband reflectance. CONCLUSIONS: The ESRT may potentially be recorded at lower presentation levels with the use of wideband reflectance measures relative to the use of acoustic immittance with a 226-Hz probe tone. This may allow for the ESRT to be obtained at levels that are more comfortable for the cochlear implant recipient, which may also allow for a higher incidence in the successful recording of the ESRT.