Role of auditory stimulation in maturation of the auditory pathway

OBJECTIVE: To compare the maturation of the auditory pathway, as shown by electrical brainstem auditory potentials (EABRs), in ears with and without prior auditory stimulation. MATERIAL AND METHODS: Electrophysiological data were collected prospectively from ears which had received cochlear implants. Implant-evoked (Imp)EABRs were recorded. Thirty children, implanted after January 2000, were selected according to a strict inclusion/exclusion protocol. All the children had received a 22-channel Nucleus cochlear implant (CI24 series). Intraoperatively, ImpEABRs were recorded using the Medelec Synergy Evoked Response system in conjunction with Nucleus Neural Response Telemetry software. The ImpEABR latencies of waves eII, eIII and eV and the morphology of wave eV were assessed. RESULTS: ImpEABRs alter during the first 12 months of life. The latency becomes shorter during this period and the morphology of wave eV alters from a broad shape to a more distinct waveform. This appears to occur independently, even in the absence of auditory stimulation. CONCLUSION: The development of electrical brainstem auditory potentials is not dependent on auditory stimulation.     

Electrically evoked auditory brainstem response monitoring of auditory brainstem implant integrity during facial nerve tumor surgery.

Evoked potentials identified as electrically evoked auditory brainstem responses (EABRs) have been recorded from a patient in response to electrical stimulation of the cochlear nucleus via an auditory brainstem implant. Recording such EABRs during surgery for removal of an ipsilateral facial nerve tumor provided a means to monitor the integrity of the implant. The presence of stable EABRs similar to those obtained before surgery indicated that the lead wires had not been severed and that the implanted electrodes had not been dislodged. EABR recording may also be useful for assisting with positioning the stimulating electrodes during initial implantation surgery, by verifying that stimulation can activate the auditory system.     

Beneficial auditory and cognitive effects of auditory brainstem implantation in children

Conclusion: This preliminary study demonstrates the development of hearing ability and shows that there is a significant improvement in some cognitive parameters related to selective visual/spatial attention and to fluid or multisensory reasoning, in children fitted with auditory brainstem implantation (ABI). The improvement in cognitive paramenters is due to several factors, among which there is certainly, as demonstrated in the literature on a cochlear implants (CIs), the activation of the auditory sensory canal, which was previously absent. The findings of the present study indicate that children with cochlear or cochlear nerve abnormalities with associated cognitive deficits should not be excluded from ABI implantation. Objectives: The indications for ABI have been extended over the last 10 years to adults with non-tumoral (NT) cochlear or cochlear nerve abnormalities that cannot benefit from CI. We demonstrated that the ABI with surface electrodes may provide sufficient stimulation of the central auditory system in adults for open set speech recognition. These favourable results motivated us to extend ABI indications to children with profound hearing loss who were not candidates for a CI. This study investigated the performances of young deaf children undergoing ABI, in terms of their auditory perceptual development and their non-verbal cognitive abilities. Patients and methods: In our department from 2000 to 2006, 24 children aged 14 months to 16 years received an ABI for different tumour and non-tumour diseases. Two children had NF2 tumours. Eighteen children had bilateral cochlear nerve aplasia. In this group, nine children had associated cochlear malformations, two had unilateral facial nerve agenesia and two had combined microtia, aural atresia and middle ear malformations. Four of these children had previously been fitted elsewhere with a CI with no auditory results. One child had bilateral incomplete cochlear partition (type II); one child, who had previously been fitted unsuccessfully elsewhere with a CI, had auditory neuropathy; one child showed total cochlear ossification bilaterally due to meningitis; and one child had profound hearing loss with cochlear fractures after a head injury. Twelve of these children had multiple associated psychomotor handicaps. The retrosigmoid approach was used in all children. Intraoperative electrical auditory brainstem responses (EABRs) and postoperative EABRs and electrical middle latency responses (EMLRs) were performed. Perceptual auditory abilities were evaluated with the Evaluation of Auditory Responses to Speech (EARS) battery – the Listening Progress Profile (LIP), the Meaningful Auditory Integration Scale (MAIS), the Meaningful Use of Speech Scale (MUSS) – and the Category of Auditory Performance (CAP). Cognitive evaluation was performed on seven children using the Leiter International Performance Scale – Revised (LIPS-R) test with the following subtests: Figure ground, Form completion, Sequential order and Repeated pattern. Results: No postoperative complications were observed. All children consistently used their devices for >75% of waking hours and had environmental sound awareness and utterance of words and simple sentences. Their CAP scores ranged from 1 to 7 (average =4); with MAIS they scored 2–97.5% (average =38%); MUSS scores ranged from 5 to 100% (average =49%) and LIP scores from 5 to 100% (average =45%). Owing to associated disabilities, 12 children were given other therapies (e.g. physical therapy and counselling) in addition to speech and aural rehabilitation therapy. Scores for two of the four subtests of LIPS-R in this study increased significantly during the first year of auditory brainstem implant use in all seven children selected for cognitive evaluation.     

Electrophysiological mapping of the cochlear nucleus with multi-channel bipolar surface microelectrodes

Auditory potentials in response to electrical stimulation of the cochlear nucleus were recorded in guinea pigs using two types of multi-channel surface microelectrodes with inter-electrode distance of 100 and 200 μm. Unequivocal waves of electrically evoked auditory brainstem responses (EABRs), which increased in amplitude with increasing stimulation current, were consistently observed. Electrophysiological mapping with these multichannel electrodes could clearly distinguish stimulation points showing positive EABRs from points showing undetectable EABRs, indicating that multi-channel surface microelectrodes have great potential in clinical use to determine the optimal location for the positioning of auditory brainstem implants, and may allow more precise discrimination of pitch. Further study to clarify the optimal inter-electrode distance for humans is necessary before application to physiological mapping in the human cochlear nucleus.     

Nucleus24型人工耳蜗使用者电诱发听神经复合动作电位的测定

目的 :探讨电诱发听神经复合动作电位 (ECAP)的特点及在人工耳蜗临床中的应用价值和意义。方法 :应用NRT(neuralresponsetelemetry)软件 ,通过体外言语处理器和耳蜗内的植入电极系统 ,采用单极模式电极刺激和近场记录方法 ,对 37例NucleusCI2 4M装置使用者进行ECAP的记录。对其中 12例使用者做了行为测试。结果 :87.6 %的使用者记录到ECAP波形。分析了有行为阈值的 12例测试者的ECAP阈值和行为阈值的关系 ,二者之间存在显著的相关性。结论 :ECAP的检出率高且波形稳定可靠 ,在临床人工耳蜗装置的调试中可作为对行为测试的补充 ;对于年幼儿童和首次开机的患者的调试尤其重要     

Distribution of fos-like immunoreactivity in the auditory pathway evoked by bipolar electrical brainstem stimulation

Objective—The auditory brainstem implant (ABI) represents a new modality for the treatment of patients deafened as a result of complete excision of a bilateral VIIIth nerve tumor. However, little work has been done on the effect of the ABI on the mammalian auditory pathway. The aim of this study was to demonstrate the effect of the ABI using Fos-like immunoreactivity.

Material and Methods—A bipolar electrode was implanted in the dorsal cochlear nucleus of bilaterally deafened Sprague–Dawley rats, and electrical stimulation was presented at an intensity four times that of threshold.

Results—Fos-like immunoreactivity was induced in the neurons of various auditory brainstem nuclei and observed in the low-to-middle frequency area. In the ipsilateral dorsal cochlear nucleus, ipsilateral posterior ventral cochlear nucleus and bilateral inferior colliculus, Fos-like immunoreactive neurons were observed as a distinct banding pattern.

Conclusions—This study showed that Fos-like immunoreactivity was observed in the restricted area of the primary brainstem auditory pathway with the appropriate tonotopicity. These results indicate that the ABI can provide auditory information suitable for speech recognition.     

Cochlear implantation in patients with auditory neuropathy of varied etiologies

OBJECTIVES/HYPOTHESIS: Auditory neuropathy is a relatively recently described pattern of hearing loss characterized by preservation of outer hair cell function despite absent brainstem auditory evoked responses. Intact outer hair cell function is demonstrated by the presence of otoacoustic emissions and/or a measurable cochlear microphonic on electrocochleography, whereas no synchronous neural activity (absent action potentials) is seen on acoustically evoked brainstem auditory evoked response testing. The study reviews the authors' experience with six patients diagnosed with auditory neuropathy, four of whom have undergone cochlear implantation. MATERIALS AND METHODS: A retrospective review of all medical and audiological charts at the University of Virginia Hospitals (Charlottesville, VA) was performed to identify patients who have undergone cochlear implantation or have been diagnosed with auditory neuropathy, or both. RESULTS: Six patients with hearing loss attributable to auditory neuropathy were identified, four of whom have undergone cochlear implantation. Causes varied, including congenital, infectious, and idiopathic origins. Adults demonstrated subjective auditory perception on promontory stimulation, whereas no repeatable brainstem auditory evoked response waveforms could be demonstrated on pediatric promontory stimulation testing. Patients with implants demonstrated implant-evoked brainstem auditory evoked responses and improved audiological performance. CONCLUSIONS: The six cases presented in the study represent varied causes and, probably, varied sites of lesions of auditory neuropathy. Promontory stimulation has been valuable, particularly in adults. Cochlear implantation allows the opportunity to provide a supraphysiological electrical stimulation to the auditory nerve, with the hope of reintroducing synchronous neural activity. Greater confidence and enthusiasm for cochlear implantation in appropriately selected patients with auditory neuropathy are gained through experience with such diverse cases.     

Abnormal Cochlear Potentials from Deaf Patients with Mutations in the Otoferlin Gene

Otoferlin is involved in neurotransmitter release at the synapse between inner hair cells (IHCs) and auditory nerve fibres, and mutations in the OTOF gene result in severe to profound hearing loss. Abnormal sound-evoked cochlear potentials were recorded with transtympanic electrocochleography from four children with otoferlin (OTOF) mutations to evaluate physiological effects in humans of abnormal neurotransmitter release from IHCs. The subjects were profoundly deaf with absent auditory brainstem responses and preserved otoacoustic emissions consistent with auditory neuropathy. Two children were compound heterozygotes for mutations c.2732_2735dupAGCT and p.Ala964Glu; one subject was homozygous for mutation p.Phe1795Cys, and one was compound heterozygote for two novel mutations c.1609delG in exon 16 and c.1966delC in exon 18. Cochlear potentials evoked by clicks from 60 to 120 dB peak equivalent sound pressure level were compared to recordings obtained from 16 normally hearing children. Cochlear microphonic (CM) was recorded with normal amplitudes from all but one ear. After cancelling CM, cochlear potentials were of negative polarity with reduced amplitude and prolonged duration compared to controls. These cochlear potentials were recorded as low as 50–90 dB below behavioural thresholds in contrast to the close correlation in controls between cochlear potentials and behavioural threshold. Summating potential was identified in five out of eight ears with normal latency whilst auditory nerve compound action potentials were either absent or of low amplitude. Stimulation at high rates reduced amplitude and duration of the prolonged potentials, consistent with neural generation. This study suggests that mechano-electrical transduction and cochlear amplification are normal in patients with OTOF mutations. The low-amplitude prolonged negative potentials are consistent with decreased neurotransmitter release resulting in abnormal dendritic activation and impairment of auditory nerve firing.     

Incidence and characteristics of facial nerve stimulation in children with cochlear implants

OBJECTIVES: Electrical stimulation from a cochlear implant can spread beyond the auditory nerve. The aims of this study were to accurately measure facial nerve stimulation in pediatric implant users and to determine the characteristics and incidence of this unwanted activity. Part A consisted of a prospective study of a randomized sample of 44 pediatric implant users. Part B consisted of a retrospective analysis of 121 children with previously recorded electrically evoked auditory brainstem responses (EABR). STUDY DESIGN AND METHODS: Responses were evoked by 3 electrodes along the implant array in three groups of children: 1) postmeningitic, 2) abnormal cochlea, and 3) neither. Intraoperative measures were obtained under anesthesia; all other recordings were completed in awake children. RESULTS: Intraoperative recordings revealed large nonauditory responses in a number of channels, including the midline EABR. Under paralysis, these responses disappeared, and clear EABRs were recorded. Similarly, prospective postoperative electromyographic (EMG) responses from the facial nerve were found in more than 59% (26 of 44) of experienced implant users (Nucleus 24): 31% of postmeningitic children (4 of 13), 80% of those with abnormal cochlea (8 of 10), and 66% of those with neither (14 of 21). Retrospective analysis of previously recorded postoperative EABRs demonstrated facial nerve stimulation in 35% (42 of 121). In most cases, facial nerve stimulation occurred when levels were perceptually loud but comfortable. CONCLUSIONS: 1) Facial nerve potentials can be recorded using EMG in a large proportion of cochlear implant users at high levels of stimulation. 2) The EABR can be obscured in the presence of facial nerve stimulation and care should be taken to distinguish it from the EMG response, particularly when auditory brainstem activity is in question. 3) Use of surface EMG provides an additional objective measure to ensure the safe and comfortable use of cochlear implants.     

Objective measurements of auditory nerve recovery function in nucleus CI 24 implantees in relation to subjective preference of stimulation rate

Objective Setting the optimal rate of stimulation for individual cochlear implant recipients is critical to the successful functional outcome of cochlear implantation. In the absence of an objective methodology, cochlear implants are currently fitted by means of a time-consuming (and therefore expensive) trial-and-error process of limited accuracy. The aim of this study was to evaluate a possible relationship between the patient's subjectively preferred stimulation rate and an objective measurement of auditory nerve recovery time.

Material and Methods Eleven recipients of Nucleus CI 24 implants initially fitted with a speech processor using the advanced combination encoders speech-coding strategy at a rate of 900 Hz were introduced to 2 other stimulation rate options, 1200 and 1800 Hz, at 2 different fitting sessions and were asked to choose their preferred rate. Preferences were compared with objective measurements of auditory nerve recovery time obtained with the refractory recovery function of neural response telemetry.

Results The auditory nerve recovery time for individuals with a subjective preference for a slow stimulation rate was longer than that for individuals who preferred a fast stimulation rate, with significant differences between the 2 groups for 3 of the tested electrodes (Nos. 7, 11 and 15): p=0.024, 0.009 and 0.03, respectively (Mann–Whitney test).

Conclusions The association observed between subjective stimulation rate preference and measurements of auditory nerve recovery time indicates that the measured auditory nerve recovery time can be used as a reliable predictor for setting up a basic stimulation rate of a particular individual's map, thus reducing the cost of the technology and significantly increasing its effectiveness.     

Activity-dependent developmental plasticity of the auditory brain stem in children who use cochlear implants

OBJECTIVES: 1) To determine if a period of early auditory deprivation influences neural activity patterns as revealed by human auditory brain stem potentials evoked by electrical stimulation from a cochlear implant. 2) To examine the potential for plasticity in the human auditory brain stem. Specifically, we asked if electrically evoked auditory potentials from the auditory nerve and brain stem in children show evidence of development as a result of implant use. 3) To assess whether a sensitive or critical period exists in auditory brain stem development. Specifically, is there an age of implantation after which there are no longer developmental changes in auditory brain stem activity as revealed by electrically evoked potentials? DESIGN: The electrically evoked compound potential of the auditory nerve (ECAP) and the electrically evoked auditory brain stem response (EABR) were recorded repeatedly during the first year of implant use in each of 50 children. The children all had pre- or peri-lingual onset of severe to profound sensorineural hearing loss and received their implants at ages ranging from 12 mo to 17 yr. All children received Nucleus cochlear implant devices. All children were in therapy and in school programs that emphasized listening and required the children to wear their implants consistently. RESULTS: Initial stimulation from the cochlear implant evoked clear responses from the auditory nerve and auditory brain stem in most children. There was no correlation between minimum latency, maximum amplitude, or slope of amplitude growth of initial responses with age at implantation for ECAP eN1, EABR eIII and eV components (p > 0.05). During the first year of implant use, minimum latency of these waves significantly decreased (p < 0.01, p < 0.0001, p < 0.0001, respectively). Neural conduction time, measured using the interwave latency of ECAP eN1-EABR eIII for lower brain stem and EABR eIII-eV for upper brain stem, decreased during the period of 6 to 12 mo of cochlear implant use (p < 0.01 (lower), p < 0.0001(upper)). The ECAP wave eN1 and the EABR wave eV showed significant increases in amplitude during time of implant use (p < 0.05 and p < 0.01, respectively). There were no correlations between the rate of interwave latency decrease and the rate of amplitude increases and the age at which children underwent implantation (p < 0.05). CONCLUSIONS: Activity in the auditory pathways to the level of the midbrain can be evoked by acute stimulation from a cochlear implant. EABR measures are not influenced by any period of auditory deprivation. Auditory development proceeds once the implant is activated and involves improvements in neural conduction velocity and neural synchrony. Underlying mechanisms likely include improvements in synaptic efficacy and possibly increased myelination. The developmental plasticity that we have shown in the human auditory brain stem does not appear from EABR data to be limited by a critical period during childhood.     

Estimation of the status of spiral ganglion neurons and Schwann cells in the auditory neural degeneration mouse using the auditory brainstem response

Conclusion: The auditory brainstem response (ABR) wave I threshold, latency and amplitude are insensitive to spiral ganglion neurons (SGNs) degeneration, but are sensitive to the degeneration of Schwann cells and can estimate the status of Schwann cells in a neural degeneration mouse model. The thorough pre-operative ABR assessment would be helpful in predicting cochlear implant performance.

Objectives: This study aimed in finding a non-invasive electrophysiological method to evaluate the status of the auditory nerve and the Schwann cells in sensorineural hearing loss (SNHL) and auditory neuropathy (AN) ears, and providing useful information for candidates screening and outcome prediction in cochlear implantation.

Methods: The frequency-specific acoustic ABR was recorded in mice. The immunohistochemical staining was performed to detect the SGNs and Schwann cells in mice cochlea. The correlations between ABR wave I metrics and SGNs, Schwann cells were investigated.

Results: In SNHL and AN mice cochlea, statistically significant correlations between ABR wave I thresholds, latencies and amplitudes at 8, 16, and 32?kHz and their corresponding SGNs densities were found only in wave I amplitude at 8?kHz. While the ABR wave I metrics at all three frequencies showed strong significant correlations with their corresponding Schwann cells densities.     

The auditory characteristics of children with inner auditory canal stenosis

Conclusions This study shows that the prevalence of auditory neuropathy spectrum disorder (ANSD) in the children with inner auditory canal (IAC) stenosis is much higher than those without IAC stenosis, regardless of whether they have other inner ear anomalies. In addition, the auditory characteristics of ANSD with IAC stenosis are significantly different from those of ANSD without any middle and inner ear malformations. Objectives To describe the auditory characteristics in children with IAC stenosis as well as to examine whether the narrow inner auditory canal is associated with ANSD. Method A total of 21 children, with inner auditory canal stenosis, participated in this study. A series of auditory tests were measured. Meanwhile, a comparative study was conducted on the auditory characteristics of ANSD, based on whether the children were associated with isolated IAC stenosis. Results Wave V in the ABR was not observed in all the patients, while cochlear microphonic (CM) response was detected in 81.1% ears with stenotic IAC. Sixteen of 19 (84.2%) ears with isolated IAC stenosis had CM response present on auditory brainstem responses (ABR) waveforms. There was no significant difference in ANSD characteristics between the children with and without isolated IAC stenosis.     

术中经蜗窗龛电刺激记录听性脑干反应方法的建立及初步应用

目的 建立人工耳蜗手术中经蜗窗龛电刺激记录听性脑干反应的方法.方法 应用自制铂铱合金球形电极作为刺激电极,改装的人工耳蜗植入体连接体外言语处理器作为电刺激仪及Bio-logic Navigator Pro诱发电位仪,对17例不同病因(包括听神经病2例、耳蜗骨化1例、内耳畸形5例、脑白质异常1例,原因不明8例),不同年龄的人工耳蜗植入患者在手术中进行测试.植入人工耳蜗装置前,将刺激电极放置在蜗窗龛内,用电荷平衡双相脉冲电流经蜗窗龛进行电刺激,记录电诱发听性脑干反应.结果 17例患者均记录到明确的电诱发听性脑干反应波形,Ⅲ波和Ⅴ波的潜伏期分别为(2.12±0.18)ms 和(4.18±0.19)ms,阈值为(220.00±16.04)CL.其中2例听神经病、5例内耳畸形、1例耳蜗骨化、1例脑白质异常患者均记录到分化良好的波形.结论 电诱发听性脑干反应是一项能够较准确地反映听觉传导通路功能完整性的客观神经电生理测试方法,对于判断人工耳蜗植入后患者能否获得听性反应,具有重要的应用价值.本研究方法的安全性符合要求,听性反应的引出率高,值得推广应用.     

Contribution from crossed and uncrossed brainstem structures to the brainstem auditory evoked potentials: A study in humans

The neural generators of the brainstem auditory evoked potentials (BAEPs) in humans are not completely known. Attempts to identify the anatomical location of the neural generators of the human BAEP based on the results of studies in animals commonly used in auditory experimentation have been difficult because of the considerable anatomical differences between the ascending auditory pathways in humans and animals. The authors of this study compared recordings obtained from different locations on the lateral side of the brainstem in six patients undergoing micro vascular decompression surgery for a cranial nerve disorder affecting the fifth cranial nerve (i.e., trigeminal neuralgia). Ipsilateral click stimulation evoked prominent responses from the caudal aspect of the pons up to the junction between the pons and the midbrain, but all components of the responses with latencies shorter than 8 msec had smaller amplitudes when recorded at more rostral locations. Components with latencies in the range of peak V elicited by contralateral click stimulation had their largest amplitudes when recorded from the lateral brainstem at the level of the fourth cranial nerve (thus, close to the inferior colliculus). Earlier components of the contralateral responses (latencies in the range of the latency of peak III) had their largest amplitudes when recorded from the caudal lateral brainstem. The results of this study indicate that the part of the uncrossed auditory pathway that is located rostral to the cochlear nucleus contributes little to the farfield potentials (i.e., BAEP), and it is doubtful whether the contralateral response that can be recorded at the level of the cochlear nucleus contributes noticeably to the BAEP.     

Effects of auditory pathway anatomy and deafness characteristics? (1): On electrically evoked auditory brainstem responses

The purpose of this study was to distinguish the effects of different parameters on latencies of wave IIIe, wave Ve, and interpeak interval IIIe-Ve of electrical auditory brainstem responses (EABRs). EABRs were recorded from all the intra-cochlear electrodes in eight adult HiRes90K((R)) cochlear implant users. The relationship between latencies and stimulation sites in the cochlea was characterized to assess activity along the auditory pathway. Audiograms before implantation, psychophysics at first fitting and duration of deafness were used to describe the influence of deafness on latencies. A decreasing baso-apical latency gradient was found for waves IIIe and Ve, while the interpeak interval IIIe-Ve remained the same along the electrode array. Electrical stimulation enabling to stimulate various parts of the cochlea at the same time, this could indicate an anatomical way of compensating for the delay the acoustic wave takes to reach the cochlea apex in a non-implanted ear. However, psychophysical levels were also found to increase at the cochlear base showing that the latency gradient could result from an increasing gradient of neural degeneration toward the base. Correlations of EABR latencies with psychophysics, audiometric data and duration of deafness show that factors linked to deafness have indeed an influence on EABR latencies. The possible explanations for the latency shift observed, whether they are anatomical and/or pathological, are exposed.     

Electrophysiologic effects of placing cochlear implant electrodes in a perimodiolar position in young children

OBJECTIVE: The purpose of this study was to intraoperatively record the electrically evoked auditory brainstem response (EABR) before and after placement of the electrode positioning system (EPS) (CII Bionic Ear with HiFocus I cochlear implant electrode array) as well as before and after stylet removal (Nucleus Contour cochlear implant electrode array). It was hypothesized that physiologic changes would occur after perimodiolar positioning of the electrode array and these changes would be evident from the EABR recordings. STUDY DESIGN: Consecutive young (11-36 month old) pediatric cochlear implant recipients (n = 17) had intraoperative EABRs recorded from three intracochlear electrodes that represented apical, medial, and basal locations. Wave V amplitudes and thresholds were studied relative to electrode location and pre- versus postperimodiolar positioning. These evoked potential measures were analyzed for statistical significance. SETTING: Tertiary referral children's hospital/medical college. RESULTS: Wave V thresholds of the EABR were lower, and amplitudes were larger after perimodiolar positioning, although the changes were dependent on electrode location and implant design. Statistically significant decreases in EABR wave V threshold and increases in suprathreshold wave V amplitude were found for the basal electrode for the CII Bionic Ear HiFocus I and for the apical electrode for the Nucleus Contour. CONCLUSIONS: Placement of either the CII Bionic Ear HiFocus I or Nucleus Contour cochlear implant electrode array in the perimodiolar position in young children resulted in less electrical current necessary to stimulate the auditory system. Changes in electrophysiologic thresholds and amplitudes, measured with EABR, indicate that the electrode array is placed closer to the modiolus with both electrode designs.     

Effects of chronic exposure to electromagnetic waves on the auditory system

Conclusion: The results support that chronic electromagnetic field exposure may cause damage by leading to neuronal degeneration of the auditory system. Objectives: Numerous researches have been done about the risks of exposure to the electromagnetic fields that occur during the use of these devices, especially the effects on hearing. The aim of this study is to evaluate the effects of the electromagnetic waves emitted by the mobile phones through the electrophysiological and histological methods. Methods: Twelve adult Wistar albino rats were included in the study. The rats were divided into two groups of six rats. The study group was exposed to the electromagnetic waves over a period of 30 days. The control group was not given any exposure to the electromagnetic fields. After the completion of the electromagnetic wave application, the auditory brainstem responses of both groups were recorded under anesthesia. The degeneration of cochlear nuclei was graded by two different histologists, both of whom were blinded to group information. Results: The histopathologic and immunohistochemical analysis showed neuronal degeneration signs, such as increased vacuolization in the cochlear nucleus, pyknotic cell appearance, and edema in the group exposed to the electromagnetic fields compared to the control group. The average latency of wave in the ABR was similar in both groups (p > 0.05).     

儿童孤独症患者脑干听觉诱发

目的通过观察儿童孤独症患者脑干听觉诱发电位的改变,探讨听觉诱发电位检测在听觉障碍儿童孤独症诊断中的临床意义.方法按DSM-IV诊断标准确诊的15例孤独症患儿和14例正常对照组,同期接受听觉诱发反应检测,比较两组间波I～V各波峰潜伏期、波峰潜伏期差和波幅的差异.结果孤独症患儿左侧波V、右侧波II峰间潜伏期和右侧I～III、I～V峰间潜伏期差较对照组显著延长(P<0.05～0.005),孤独症组右侧波III振幅较对照组增高(P<0.05),其他各指标两组间无显著性差异.结论孤独症患儿脑干听觉诱发电位的突出改变是潜伏期有延长的趋势;对就诊于耳鼻咽喉科的听阈正常而有听觉障碍,言语交往能力差,脑干听觉诱发电位检查潜伏期延长的儿童,应警惕孤独症或其他神经精神发育障碍.