Electrophysiological characterisation of envelope-following responses

IntroductionThe auditory ability to discriminate rapid changes in the envelope of language sounds is essential for speech comprehension. This ability is deteriorated in some neurological diseases such as multiple sclerosis, auditory neuropathy, sensorineural hearing loss, presbycusis and primary developmental language disorder. Envelope-following responses (EFRs) in humans are useful in objective measurement of temporal processing in the auditory nervous system.ObjectivesTo evaluate EFRs in healthy younger subjects and to investigate the effects of subject states on the EFRs recorded.MethodsEleven young subjects were included; six of them were awake and five were asleep. EFRs were evoked by white noise carrier stimuli with a sweep of modulation frequencies from 20 to 200 Hz presented at 50 dB HL.ResultsThe EFRs we recorded were similar in all subjects. There were two principal components. During both subject sleep and wakefulness, the first component (located between 30-50 Hz) was significantly larger than the second component (located between 80-110 Hz). There was also a significant effect of sleep on the EFR amplitude for the modulation frequencies between 88-110, 155-165 and 190-200 Hz. However, there were no significant effects of sleep on the principal EFR components.ConclusionsThese results corroborate the usefulness of the EFR technique for objective measurement of human auditory temporal processing.     

Newborn hearing screening test with multiple auditory steady-state responses

IntroductionThe techniques most frequently used within a screening context (otoacoustic emissions and click auditory brainstem response) have well-known limitations in hearing loss detection.ObjectiveThis study examines the feasibility of a semi-automated multiple auditory steady-state responses (MSSR) system designed for neonatal hearing screening.MethodsA sample of 50 newborns without risk factors (well-babies) was tested within two weeks of birth. All had detectable auditory brainstem responses to clicks down to 40 dB nHL in both ears. Two amplitude modulated carrier tones of 500 and 2,000 Hz were mixed together and presented simultaneously. Each infant (and ear) was screened with the MSSR system; to simulate a hearing loss, a recording without stimulation was also obtained.ResultsMean auditory thresholds were 42.5 ± 7 dB HL at 500 Hz and 35.5 ± 6 dB HL at 2,000 Hz. The average duration of the MSSR recording was 2.6 ± 1.6 minutes for each tested ear and the overall duration of the screening procedure (including electrode fitting and infant preparation) was 17.8 ± 3.7 minutes. The diagnostic sensibility and the positive predictive values of the MSSR semi-automatic screening system was 100% and 96% respectively, with specificity of 96% and negative predictive values of 100%.ConclusionsAlthough the diagnostic efficiency of the semi-automated MSSR system was found adequate, further technological improvements are still necessary to facilitate its use in the context of universal newborn hearing screening program.     

Maturational changes in the human envelope-following responses

IntroductionThe auditory ability to discriminate rapid changes in the envelope of language sounds is essential for speech comprehension. Human envelope-following responses (EFRs) are useful for objective measurement of temporal auditory processing in subjects who are unable to give accurate behavioural responses (e.g., young children).ObjectiveTo evaluate age-dependent changes in EFRs during the first 2 years of life.MethodsThe EFRs were recorded in a sample of 16 well babies distributed into 2 age groups (G1: 12 newborns; G2: 4 babies of 2 years). The EFRs were evoked by white noise carrier stimuli with a sweep of modulation frequencies from 20 to 200 Hz presented at 50 dB HL.ResultsThe age-related changes affected both morphology and EFR detectability. The main morphological differences were at the expense of frequencies below 50 Hz, where the first component P1 was not well defined in either of the 2 age groups. For all modulation frequencies, age significantly affected EFR amplitude and detectability.ConclusionsThe present study provides the first evidence on EFR maturation. Some understanding of normal EFR development would facilitate a better use of this technique in clinically-objective measurement of auditory temporal processing in infants who cannot provide reliable behavioural responses.     

High levels of sound pressure: acoustic reflex thresholds and auditory complaints of workers with noise exposure

IntroductionThe clinical evaluation of subjects with occupational noise exposure has been difficult due to the discrepancy between auditory complaints and auditory test results. This study aimed to evaluate the contralateral acoustic reflex thresholds of workers exposed to high levels of noise, and to compare these results to the subjects’ auditory complaints.MethodsThis clinical retrospective study evaluated 364 workers between 1998 and 2005; their contralateral acoustic reflexes were compared to auditory complaints, age, and noise exposure time by chi-squared, Fisher's, and Spearman's tests.ResultsThe workers’ age ranged from 18 to 50 years (mean = 39.6), and noise exposure time from one to 38 years (mean = 17.3). We found that 15.1% (55) of the workers had bilateral hearing loss, 38.5% (140) had bilateral tinnitus, 52.8% (192) had abnormal sensitivity to loud sounds, and 47.2% (172) had speech recognition impairment. The variables hearing loss, speech recognition impairment, tinnitus, age group, and noise exposure time did not show relationship with acoustic reflex thresholds; however, all complaints demonstrated a statistically significant relationship with Metz recruitment at 3000 and 4000 Hz bilaterally.ConclusionThere was no significance relationship between auditory complaints and acoustic reflexes.     

Azimuthal sound source localization of various sound stimuli under different conditions

AimTo evaluate azimuthal sound-source localization performance under different conditions, with a view to optimizing a routine sound localization protocol.Material and methodTwo groups of healthy, normal-hearing subjects were tested identically, except that one had to keep their head still while the other was allowed to turn it. Sound localization was tested without and then with a right ear plug (acute auditory asymmetry) for each of the following sound stimuli: pulsed narrow-band centered on 250 Hz, continuous narrowband centered on 2000 Hz, 4000 Hz and 8000 Hz, continuous 4000 Hz warble, pulsed white noise, and word (“lac” (lake)). Root mean square error was used to calculate sound-source localization accuracy.ResultsWith fixed head, localization was significantly disturbed by the earplug for all stimuli (P < 0.05). The most discriminating stimulus was continuous 4000 Hz narrow-band: area under the ROC curve (AUC), 0.99 [95% CI, 0.95–1.01] for screening and 0.85 [0.82–0.89] for diagnosis. With mobile head, localization was significantly better than with fixed head for 4000 and 8000 Hz stimuli (P < 0.05). The most discriminating stimulus was continuous 2000 Hz narrow-band: AUC, 0.90 [0.83–0.97] for screening and 0.75 [0.71–0.79] for diagnosis. In both conditions, pulsed noise (250 Hz narrow-band, white noise or word) was less difficult to localize than continuous noise.ConclusionThe test was more sensitive with the head immobile. Continuous narrow-band stimulation centered on 4000 Hz most effectively explored interaural level difference. Pulsed narrow-band stimulation centered on 250 Hz most effectively explored interaural time difference. Testing with mobile head, closer to real-life conditions, was most effective with continuous narrow-band stimulation centered on 2000 Hz.     

Effect of contralateral stimulation on acoustic reflectance measurements

IntroductionAcoustic reflectance is an important tool in the assessment of middle ear afflictions, and the method is considered advantageous in relation to tympanometry. There has been a growing interest in the study of contralateral acoustic stimulation and its effect on the activation of the efferent auditory pathway. Studies have shown that the introduction of simultaneous stimulation in the contralateral ear generates alterations in auditory response patterns.ObjectiveTo investigate the influence of contralateral stimulation on acoustic reflectance measurements.MethodsCase study of 30 subjects with normal hearing, of both genders, aged 18–30 years. The test and retest acoustic reflectance was conducted in the frequency range 200–6000 Hz. The procedure was repeated with the simultaneous presence of contralateral white noise at 30 dBNS.ResultsThe analysis of the conditions of test, retest, and test with contralateral noise showed statistical difference at the frequency of 2 kHz (p = 0.011 and p = 0.002 in test and retest, respectively) in the right ear.ConclusionThe activation of the auditory efferent pathways through contralateral acoustic stimulation produces alterations in response patterns of acoustic reflectance, increasing sound reflection and modifying middle ear acoustical energy transfer.     

A new genetic variant causing auditory neuropathy: A CARE case report

IntroductionAuditory neuropathy refers to impaired synchronization of the auditory signal along the cochlear nerve. The present study, following CARE case report guidelines, describes a case of auditory neuropathy secondary to a genetic variant not previously described.ObservationAn 18-year-old patient was followed for multiple learning disorder. His main complaint was speech comprehension, especially in noise. Auditory neuropathy was diagnosed on electrophysiological criteria, linked to a 2.66 Mb deletion on the short arm of chromosome 16, at 16p13.11p12.3 (15,492,317-18,162,167, according to the hg19 version of the human reference genome). Adapted speech therapy sessions with auditory training for intelligibility in noise and a hearing aid with high-frequency microphone were prescribed. At 6 months, the patient reported improvement in understanding speech in noise.ConclusionThe involvement of this 16p13.11 deletion in the patient's symptomatology was not obvious, in a probable context of incomplete penetrance and variable expression. Early diagnosis of auditory neuropathy allowed implementation of better adapted multidisciplinary specialized management.     

Automated analysis of bone-conduction cortical auditory evoked potential in normal-hearing neonates

IntroductionThe cortical auditory evoked potential allows the possibility of objectively evaluating the entire auditory system, which is desirable in the pediatric population. Bone conduction auditory stimulation is recommended in the differential diagnosis of conductive hearing loss. However, there are not many studies of cortical auditory evoked potential using bone conduction.ObjectiveThe aim of this study was to characterize the response of cortical auditory evoked potential through bone conduction in normal-hearing neonates using an automated response analysis equipment.MethodsThis study included 30 normal-hearing neonates, without risk factors for hearing loss. The equipment used was the HEARlab automated response analysis and the cortical responses were evaluated at the frequencies of 500–4000 Hz through bone conduction, at intensity ranging from 0 to 60 dBnHL. The latencies and amplitudes were manually marked by experienced judges.ResultsCortical auditory evoked potential responses were detected in 100% of the evaluated subjects and there was no difference regarding the cortical response of the neonates in relation to the variables of gender, ear and masking use. At an intensity of 60 dBnHL for the frequencies of 500, 1000, 2000 and 4000 Hz the latencies were 234; 241; 239 and 253 ms and the amplitudes were 15.6; 8.4; 6.2; 6.3 μV. The mean thresholds were 23.6; 28; 31 and 33.1 dBnHL, respectively.ConclusionIt was possible to measure the cortical auditory evoked potential response in the neonatal population using bone vibrator as sound transducer and to draw the profile of the cortical auditory evoked potential latencies and amplitudes by frequencies at the intensity of 60 dBnHL and at the threshold.     

Cortical auditory evoked potential in assessment of neonates: a study about minimum level of responses in term and preterm newborns

IntroductionThe study of the threshold level of cortical auditory response in adults has been investigated in previous studies. Due to maturational issues, little is known about these responses in neonates. Technological advances with automatic analysis devices now allow investigation in specific populations. Thus, new studies are needed to establish the feasibility of using this auditory potential to identify the lowest levels of responses in children.ObjectiveVerify and compare latency and amplitude in 80 dBnNA and the minimum level of cortical auditory response in term and preterm neonates.MethodsA cross-sectional, comparative study involving 59 neonates, 35 full-term births and 24 preterm births, with positive results in the Neonatal Hearing Screening. The Hearlab system was used to investigate the P1i auditory potential with tone burst stimulus at frequencies of 500, 1000, 2000 and 4000 Hz. The minimum response level search ranged from 80 to 0 dBNA and was detected automatically. The results were compared between groups, evaluating the latency and amplitude in 80 dBNA and the minimum level of cortical auditory response.ResultsThe mean values obtained for the minimum level of cortical auditory response in term group were 26 ± 8.81; 26.14 ± 6.97; 29 ± 7.65 and 29.43 ± 7.04 dBNA and for preterm neonates of 31.96 ± 10.41; 34.13 ± 11.34; 33.64 ± 11.03 and 37.73 ± 11.92 dBNA, for the frequencies of 500, 1000, 2000 and 4000 Hz, respectively. There was a difference between groups for the latency of P1i at 4000 Hz and the minimum response levels at 500, 1000 and 4000 Hz, with higher values for preterm infants.ConclusionIt was possible to obtain latency and amplitude values at 80 dBnNA and the minimum level of cortical response in term and preterm newborns, with different results between groups, with higher values in those born preterm.     

Representation of amplified speech at cortical level in good and poor hearing aid performers

IntroductionHearing aid users reject their own hearing aid because of annoyance with background noise. The reason for dissatisfaction is located anywhere from the hearing aid microphone to the integrity of neurons along the auditory pathway. In this preview, the output of hearing aid was recorded at the level of ear canal and at auditory cortex in good and poor hearing aid users, who were classified using acceptable noise level.ObjectiveTo study the representation of amplified speech in good and poor hearing aid performers.MethodsA total of 60 participants (age ranged 15–65 years) with moderate bilateral sensorineural hearing impairment grouped into good (n = 35) and poor (n = 25) hearing aid performers. Gap detection test and aided SNR 50 were administered. In addition, ear canal acoustic measures and cortical auditory evoked potentials were recorded in unaided and aided conditions at 65 dB SPL.ResultsHearing aid minimally alters temporal contrast of speech reflected in envelope difference index. Although having similar temporal impairment, acoustic characteristics of amplified speech sounds and SNR 50 scores from both groups, the aided cortical auditory evoked potentials surprisingly showed significant earlier latencies and higher amplitudes in good performers than poor performers. In addition, good and poor performers classified based on annoyance level was predicted by latencies of 2N1 and 2P2 components of acoustic change complex. Further, a follow-up revealed hearing aid use has relation with acceptance towards noise.ConclusionParticipants who are willing to accept noise from those who are not willing to accept noise have subtle physiological changes evident at the auditory cortex, which supports the hearing aid usage.     

EFFECTS OF MODERATE NOISE EXPOSURE ON HEARING FUNCTION IN C57BL/6J MICE

Objective To study characteristics of hearing loss after exposure to moderate noise exposure in C57BL/6J mice. Methods Male C57BL/6J mice with normal hearing at age of 5-6 weeks were chosen for this study. The mice were randomly sclccted to be studied immediately after exposure （Group P0）, or 1 day （Group P1）, 3 days （Group P3）, 7 day （Group P7） or 14 days （P14） after exposure. Their before exposure condition served as the normal control. All mice were exposed to a broad-band white noise at 100 dB SPL for 2 hours, ABR thresholds were used to estimate hearing status at each time point. Results ABR threshold elevation was seen at every tested frequency at P0 （P〈0.01）. Elevation at high-frequencies （16 kHz and 32 kHz） was greater than at lower frequencies （4 kHz and 8 kHz, P〈0.05）. From P1 to P14, ABR thresholds continuously improved, and there was no significant difference between P14 and before exposure （P〉0.05）. Conclusion There is a frequency specific re- sponse to 100 dB SPL broad-band white noise in C57BL/6J mice, with the high-frequency being more susceptible. Hearing loss induced by moderate noise exposure appears reversible in C57BL/6J mice.     

Cortical auditory responses according to hearing rehabilitation in unilateral hearing loss

ObjectiveTo assess the impact of rehabilitation systems (CROS: Contralateral Routing of Signal; BAHA: Bone-Anchored Hearing Aid; CI: cochlear implant) on cortical auditory evoked potentials (CAEP) and auditory performance in unilateral hearing loss.Subjects and methodTwenty-one adults with unilateral hearing loss, using CROS (n = 6), BAHA (n = 6) or CI (n = 9), were included. Seven normal-hearing subjects served as controls. CAEPs were recorded for a (/ba/) speech stimulus; for patients, tests were conducted with and without their auditory rehabilitation. Amplitude and latency of the various CAEP components of the global field power (GFP) were measured, and scalp potential fields were mapped. Behavioral assessment used sentence recognition in noise, with and without spatial cues.ResultsOnly CI induced N1 peak amplitude change (P < 0.05). CI and CROS increased polarity inversion amplitude in the contralateral ear, and frontocentral negativity on the scalp potential map. CI improved understanding when speech was presented to the implanted ear and noise to the healthy ear, and vice-versa.ConclusionCochlear implantation had the greatest impact on CAEP morphology and auditory performance. A longitudinal study could analyze progression of cortical reorganization.     

Análisis de la potencia de salida y del rendimiento auditivo de los dispositivos auditivos osteointegrados

Background and objectiveOsseointegrated auditory devices are hearing gadgets that use the bone conduction of sound to produce hearing improvement. The mechanisms and factors that contribute to this sound transmission have been widely studied, however, there are other aspects that remain unknown, for instance, the influence of the processor power output. The aim of this study was to know if there is any relationship between the power output created by the devices and the hearing improvement that they achieve.Materials and methodsForty-four patients were implanted with a percutaneous Baha® 5 model. Hearing thresholds in pure tone audiometry, free-field audiometry, and speech recognition (in quiet and in noise) were measured pre and postoperatively in each patient .The direct bone conduction thresholds and the power output values from the processors were also obtained.ResultsThe pure tone average threshold in free field was 39.29 dB (SD 9.15), so that the mean gain was 29.18 dB (SD 10.13) with the device. This involved an air-bone gap closure in 63.64% of patients. The pure tone average threshold in direct bone conduction was 27.6 dB (SD 10.91), which was 8.4 dB better than the pure tone average threshold via bone conduction. The mean gain in speech recognition was 39.15% (SD 23.98) at 40 dB and 36.66% (SD 26.76) at 60 dB. The mean gain in the signal-to-noise ratio was ?5.9 dB (SD 4.32). On the other hand, the mean power output values were 27.95 dB μN (SD 6.51) in G40 and 26.22 dB μN (SD 6.49) in G60. When analysing the relationship between bone conduction thresholds and G40 and G60 values, a correlation from the frequency of 1,000 Hz was observed. However, no statistically significant association between power output, functional gain or speech recognition gain was found.ConclusionsThe osseointegrated auditory devices generate hearing improvement in tonal thresholds and speech recognition, even in noise. Most patients closed the air-bone gap with the device. There is a direct relationship between the bone conduction threshold and the power output values from the processor, but only in mid and high frequencies. However, the relationship between power output and gain in speech recognition is weaker. Further investigation of contributing factors is necessary.     

Gender differences in binaural speech-evoked auditory brainstem response: are they clinically significant?

IntroductionBinaurally evoked auditory evoked potentials have good diagnostic values when testing subjects with central auditory deficits. The literature on speech-evoked auditory brainstem response evoked by binaural stimulation is in fact limited. Gender disparities in speech-evoked auditory brainstem response results have been consistently noted but the magnitude of gender difference has not been reported.ObjectiveThe present study aimed to compare the magnitude of gender difference in speech-evoked auditory brainstem response results between monaural and binaural stimulations.MethodsA total of 34 healthy Asian adults aged 19–30 years participated in this comparative study. Eighteen of them were females (mean age = 23.6 ± 2.3 years) and the remaining sixteen were males (mean age = 22.0 ± 2.3 years). For each subject, speech-evoked auditory brainstem response was recorded with the synthesized syllable /da/ presented monaurally and binaurally.ResultsWhile latencies were not affected (p > 0.05), the binaural stimulation produced statistically higher speech-evoked auditory brainstem response amplitudes than the monaural stimulation (p < 0.05). As revealed by large effect sizes (d > 0.80), substantive gender differences were noted in most of speech-evoked auditory brainstem response peaks for both stimulation modes.ConclusionThe magnitude of gender difference between the two stimulation modes revealed some distinct patterns. Based on these clinically significant results, gender-specific normative data are highly recommended when using speech-evoked auditory brainstem response for clinical and future applications. The preliminary normative data provided in the present study can serve as the reference for future studies on this test among Asian adults.     

The effect of very low dose pulsed magnetic waves on cochlea

IntroductionIn daily life biological systems are usually exposed to magnetic field forces at different intensities and frequencies, either directly or indirectly. Despite negative results, the therapeutic use of the low dose magnetic field has been found in recent studies. The effect of magnetic field forces on cochlear cells is not clear in the literature.ObjectiveIn our study, we first applied in vivo pulsed magnetic fields to laboratory rats to investigate the effects on cochlea with distortion product otoacoustic emission test followed by histopathological examinations.MethodsTwelve rats were included in this study, separated into two groups as study group and control group. The rats in the study group were exposed to 40 Hz pulsed magnetic field for 1 h/day for 30 days; the hearing of the rats was controlled by otoacoustic emission test. Also, their cochleas were removed and histochemical examination was performed by Caspase-3, Caspase-9, and TUNEL methods.ResultsA statistically significant difference was determined (p < 0.05) when the hearing thresholds of the groups obtained by using 5714 Hz and 8000 Hz stimuli were compared by Kruskal–Wallis test. A significant reaction was observed in the study group, especially in the outer ciliated cells during immunohistochemical examinations by using Caspase-3 and Caspase-9 methods. A significantly positive difference was determined in the study group, especially at the outer ciliated cells and the support cells of the corti organ, when compared to the control group (p < 0.05) by the TUNEL method.ConclusionAccording to the results of our study, the very low dose magnetic field, which is considered to be used for therapeutic purposes recently, can cause both auditory function defects and histopathologic damage in cochlear cells.     

The characteristic of otoacoustic emissions in full-term neonates according to ABO blood groups

IntroductionPrevious research has suggested that individuals with different blood groups show varied incidences of noise-induced hearing loss. The reduced otoacoustic emissions amplitudes indicate the higher possibilities of outer hair cell damage for noise exposure.ObjectiveThe objective is to analyze the characteristics of otoacoustic emissions, including the occurrence of spontaneous otoacoustic emission and the amplitudes of distortion product otoacoustic emission at certain frequencies in full term neonates with different ABO blood groups.MethodsA total of 80 selected full-term female neonates who passed the initial newborn hearing screen were enrolled into the study, with equal number of participants in four ABO blood groups (Blood Group A, Blood Group B, Blood Group AB, Blood Group O). Measurements of spontaneous otoacoustic emission and distortion product otoacoustic emission were performed in both ears for all participants.Results(1) The blood group O participants showed significantly fewer spontaneous otoacoustic emission occurrences than the other three blood groups (A = 70%, B = 80%, AB = 67%, O = 25%, p <  0.05). (2) The blood group O participants showed lower DPOAE amplitudes at 1257 Hz (M = 4.55 dB, SD = 8.36), 1587 Hz (M = 11.60 dB, SD = 6.57), 3174 Hz (M = 7.25 dB, SD = 5.99), 5042 Hz (M = 13.60, SD = 6.70) than participants with the other three blood groups in left ears (p < 0.05). In right ears, the blood group O participants showed reduced amplitudes at 1257 Hz (M = 6.55 dB, SD = 8.36), 1587 Hz (M = 13.60 dB, SD = 6.57), 3174 Hz (M = 7.65 dB, SD = 6.43), 5042 Hz (M = 13.65 dB, SD = 6.50) than participants from non-O blood groups (p < 0.05).ConclusionFemale individuals with blood group O have lower otoacoustic emissions values than individuals with the other three blood groups. We need to further investigate the possible relationships between ABO blood group and cochlear function, including the potential influences of noise damage on cochlear outer hair cells.     

Evaluation of the impact of hearing loss in adults: Validation of a quality of life questionnaire

ObjectivesThe impact of hearing loss and of auditory rehabilitation (hearing aid, cochlear implant) on quality of life is a crucial issue. Commonly used questionnaires to assess quality of life in these patients (Nijmegen, APHAB, GBI) are time-consuming, difficult for patients to fill out, and show poor sensitivity to small improvements or deterioration. The objective of the present study was to validate a dedicated quality of life scale for hearing-impaired adults with or without auditory rehabilitation.Material and methodsERSA (Évaluation du Retentissement de la Surdité chez l’Adulte: Evaluation of the Impact of Hearing Loss in Adults) is a self-administered questionnaire. It is divided into 4 domains, each comprising 5 questions graded from 1 to 10. The questions are simple, and formulated so patients will answer according to how they feel at the actual time of the session. Test-retest reliability was measured in 38 patients. Internal coherence and validity against the APHAB questionnaire as gold standard and in relation to hearing performance were measured in 122 patients at auditory assessment. Sensitivity to change in hearing was measured in 36 cochlear implant patients, before and 6 or 12 months after implantation.ResultsTest-retest reliability was very satisfactory (ρ = 0.88). Internal coherence was good for all questions. External validity, comparing ERSA to APHAB scores in the same non-implanted hearing-impaired patients, was good (ρ = 0.52). Additionally, ERSA scores correlated with hearing performance in adverse conditions (monosyllabic words: ρ = 0.22; sentences in noise: ρ = 0.19). In patients tested before and after cochlear implantation, improvement in hearing performance in silence and in noise correlated with an improvement in ERSA score (ρ = 0.37 to 0.59, depending on the test), but not to GBI score.ConclusionThe ERSA questionnaire is easy and quick to use, reliable, and sensitive to change in hearing performance after cochlear implantation.     

Prevalence of potential candidates for electric-acoustic stimulation implant in a hearing-impaired population

ObjectiveTo estimate the prevalence of potential electric-acoustic stimulation (EAS) implant candidates in a hearing-impaired population through a review of auditory examinations.MethodsIn total, 7356 patients underwent audiometric examination in our department between 2011 and 2014. The prevalence of patients meeting the audiometric criteria for EAS and standard cochlear implant (CI) was assessed.ResultsThe percentage of EAS implant candidates meeting the pure-tone audiometric criteria was 0.71% (n = 34) among the hearing-impaired individuals (n = 4758) examined in our department, whereas 2.52% (n = 120) met the criteria for standard CI. Among the 34 EAS implant candidates, 2 individuals (5.83%) received EAS implant surgery after approval of the EAS device in Japan.ConclusionsThere was a lower prevalence of EAS implant candidates than standard CI candidates. Nevertheless, healthcare professionals should carefully examine the audiograms of patients with high frequency hearing loss with regard to meeting the indication criteria for EAS implant. This will enable patients to gain access to adequate information relating to further examinations and treatment options.     

Resultados en el estudio del córtex auditivo mediante resonancia magnética funcional (I): características generales y resultados individuales

ObjectiveTo demonstrate and investigate the activation patterns of the primary auditory cortex (Heschl's gyrus) using functional magnetic resonance imaging (fMRI).Material and methodsPure tone stimuli at 750 Hz and 2000 Hz were delivered to the right and left ear of 32 normal-hearing volunteers (18-49 years old) in 20-second on-off cycles. The fMRI data were obtained using a 1.5 Tesla scanner and processed with SPM2.ResultsFor both tone frequencies, bilateral hemispheric activation was identified in the transverse temporal gyrus (Heschl's gyrus) in 29 subjects (90.62 %) in response to pure tone stimuli with a probability level of p < 0.001. For monaural stimulation, bilateral hemispheric activation was observed with generally greater extent of activation in the Heschl's gyrus (HG) contralateral to the stimulated ear.ConclusionsThese results demonstrate that fMRI is a useful imaging technique to investigate the auditory cortex. The contralateral auditory cortex is more responsive than the ipsilateral cortex to tones presented monaurally.