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PubMed2002

Clinical and audiological features in auditory neuropathy.

OBJECTIVE: To medically and audiologically characterize a population of children diagnosed as having auditory neuropathy (AN). STUDY DESIGN: Retrospective medical chart review. SETTING/SUBJECTS: We identified 22 patients from a pediatric otology clinic in a tertiary care pediatric hospital setting. RESULTS: A genetic factor in AN is suggested by our identification of 3 families with 2 affected children and 2 other children with family histories that were positive for hearing loss. Clinical features common among our population included a history of hyperbilirubinemia (n = 11 [50%]), prematurity (n = 10 [45%]), ototoxic drug exposure (n = 9 [41%]), family history of hearing loss (n = 8 [36%]), neonatal ventilator dependence (n = 8 [36%]), and cerebral palsy (n = 2 [9%]). Full clinical and audiological data were available for 18 of the 22 children, including otoacoustic emissions, auditory brainstem responses with cochlear microphonics, and age-appropriate audiometric findings. Significantly, 9 of these 18 patients showed improvement in behavioral thresholds over time, indicating that a subset of children with AN may recover useful hearing levels. Also significant was the success of cochlear implantation in 4 children. CONCLUSIONS: Management of AN in children requires serial clinical and audiometric evaluations, with a prominent role for behavioral testing. Prematurity, genetics, and hyperbilirubinemia appear to be significant factors in the development of AN; hyperbilirubinemia can be associated with spontaneous improvement of hearing thresholds. For those children not benefiting from amplification or FM systems, cochlear implantation remains a potentially successful method of habilitation.

Audiometry↗
PubMed2003

"Auditory neuropathy": physiologic and pathologic evidence calls for more diagnostic specificity.

The term "auditory neuropathy" is being used in a rapidly increasing number of papers in the audiology/otolaryngology literature for a variety of individuals (mostly children) who fulfill the following criteria: (1) understanding of speech worse than predicted from the degree of hearing loss on their behavioral audiograms; (2) recordable otoacoustic emissions and/or cochlear microphonic; together with (3) absent or atypical auditory brain stem responses. Because of the general lack of anatomic foundation for the label "auditory neuropathy" as currently used, we review the anatomy of the auditory pathway, the definition of neuropathy and its demyelinating, axonal, and mixed variants. We submit that the diagnostic term "auditory neuropathy" is anatomically inappropriate unless patients have documented evidence for selective involvement of either the spiral ganglion cells or their axons, or of the 8th nerve as a whole. In view of biologic differences between peripheral nerves and white matter tracts in the brain, the term "auditory neuropathy" is inappropriate for pathologies affecting the central auditory pathway in the brainstem and brain selectively. Published reports of patients with "auditory neuropathy" indicate that they are extremely heterogeneous in underlying medical diagnosis, age, severity, test results, and that only a small number have undergone the detailed investigations that would enable a more precise diagnosis of the locus of their pathologies. The electrophysiology of peripheral neuropathies and the deficits expected with pathologies affecting the hair cells, spiral ganglion cells and their axons (auditory neuropathy sensu stricto), and brain stem relays are reviewed. In order to serve patients adequately, including potential candidates for cochlear implants, and to increase knowledge of auditory pathologies, we make a plea for more comprehensive evaluation of patients who fulfill the currently used audiologic criteria for "auditory neuropathy" in an effort to pinpoint the site of their pathologies. We suggest that the term auditory neuropathy be limited to cases in which the locus of pathology is limited to the spiral ganglion cells, their processes, or the 8th nerve, and that the term neural hearing loss be considered for pathologies that affect all higher levels of the auditory pathway, from the brainstem to the auditory cortex.

Audiology↗
PubMed1997

[Laser vibrometry. A middle ear and cochlear analyzer for noninvasive studies of middle and inner ear function disorders].

A complete battery of audiometric methods is required for the differential diagnosis of different hearing disabilities (including puretone audiometry, impedance, stapes reflex, speech audiometry, brainstam evoked response audiometry, otoacoustic emissions, etc.). In many cases, a comprehensive diagnosis is not possible. Here we describe a new technique based on a laser-Doppler vibrometer that has the potential for non-invasive diagnosis not only middle ear disease but also cochlear pathologies. Disturbance of cochlear function can be ascertained because the input impedance of the cochlea acts as a mechanical load on the middle ear and therefore influences motion of the umbo. In the present study vibration of the umbo and eardrum were measured with a commercially available laser-Doppler vibrometer coupled directly into a standard surgical microscope. The use of the microscope allowed non-invasive measurements of vibrations without having to introduce reflecting material onto the tympanic membrane. Sound pressure was measured with a calibrated probe microphone placed near the tympanic membrane. The displacement response and the specific acoustic impedance of the umbo were calculated from the velocity and sound pressure measured. For normal hearing subjects, the amplitude of the umbo's displacement for frequencies from 0.1 kHz to 1 kHz was 1 nm at 60 dB SPL and decreased with a slope of 6 dB/octave for frequencies between 1 and 5 kHz. A strong correlation was found between the specific acoustic impedance of the umbo and hearing thresholds for hearing-impaired subjects (having otosclerosis or sensorineural hearing losses). The frequency response of the umbo proved to be a means for evaluating the function of both the middle ear and the cochlea under pathological conditions. The measurement technique described is also suitable for intraoperative investigation of the frequency response of the opened middle ear, as well as for the in situ frequency response of partial and total ossicular replacement prostheses.

Acoustic Impedance Tests↗
PubMedDate not supplied

[The effects of methodical factors on the microphonic potential in the guinea pig cochlea with perfusion of perilymph].

The decreas in microphonic potentials detected from the round window (RMP) is negligible only if the bores are located very close to the round window, whereas it will increase with increasing distance from it. Only at pressures of more than +/- 30 cm water column, in rare cases even below that, will a sharp decrease in the RMP occur, possibly because of a lesion of either the oval or the round windown membrane. At a perfusion pressure above +5.6 cm water column, the perfusion liquid will enter the cerebrospinal fluid space. At a lower pressure the perfusion liquid is diluted by cerebrospinal fluid via the cochlear aqueduct. The perfusion speed of 1 to 50 mul/min has no effect on the function of the organ of Corti.

Action Potentials↗
PubMedDate not supplied

Large vestibular aqueduct syndrome: a case study.

A 23-month-old female was referred for hearing aid fitting after failing newborn hearing screening and being diagnosed with significant hearing loss through subsequent diagnostic testing. Auditory brainstem response (ABR) and behavioral testing revealed a moderate-to-severe bilateral mixed hearing loss. Prior to the hearing aid evaluation, tympanostomy tubes had been placed bilaterally with little or no apparent change in hearing sensitivity. Initial testing during the hearing aid fitting confirmed earlier findings, but abnormal middle ear results were observed, requiring referral for additional otologic management. Following medical clearance, binaural digital programmable hearing aids were fit using Desired Sensation Level parameters. Behavioral testing and probe microphone measures showed significant improvements in audibility. Decrease in hearing sensitivity was observed six months following hearing aid fitting. Radiological studies, ordered due to the mixed component and decreased hearing sensitivity, revealed large vestibular aqueduct syndrome (LVAS). Based on the diagnosis of LVAS, a cochlear implant was placed on the right ear; almost immediate speech-language gains were observed.

Child Language↗
PubMed1998

[Development and clinical testing of a non-magnetic cochlear implant. Preliminary experimental studies and surgical concept. Results in the first 10 patients].

BACKGROUND: To ensure good transmission of electromagnetic signals from the speech processor to the internal cochlear stimulator (ICS) in cochlear implants, exact alignment of the external transmitter coil over the receiver coil of the ICS is necessary. Usually this is achieved by two magnets: one implanted within the ICS, the other one integrated into the transmitter coil of the external headset. Although this principle works, there are some serious problems with the implanted magnet. The most serious of these is that it renders MRI studies potentially hazardous or impossible, or at least compromises image quality. METHOD AND RESULTS: We developed a method to eliminate the magnet. The method requires varying the implantation technique and using a special headset. The technique is easy to perform, and the headset is suitable for series production. Experience with our first patients revealed the coil alignment to be remarkably stable, even more than in patients with a cochlear implant equipped with a magnet. Results of the first ten patients are presented. DISCUSSION: Aside from eliminating the magnet, we attempted to optimize the acoustic properties of the headset. This resulted in design changes such as repositioning the microphone. Further improvements such as integration of telephone coils and special sockets to connect peripheral appliances can easily be implemented in our special headset.

Adult↗
PubMed2006

[A multicentre comparative study of the ESPrit and the Nucleus 22].

BACKGROUND: Cochlear implant recipients often report additional difficulty in comprehension of speech in noisy conditions and of softly spoken speech. The aim of this clinical study was to evaluate and compare the performance advantages offered by the ear level ESPrit 3G for experienced Nucleus Mini 22 cochlear implantees. PATIENTS AND METHODS: Twenty-eight German-speaking implanted subjects, who had had experience with either the Spectra 22 or the ESPrit 22 for at least 6 months, were evaluated with their current processor and the ESPrit 3G (on microphone, M, and whisper, W, settings) following a 4-week trial. Freiburger monosyllabic words (FMW) were used at soft and conversational levels in quiet conditions and Oldenburger sentences (OLSA) were used in noisy conditions to compare performance. Subjective impressions of sound quality and user aspects were evaluated and combined with data from 31 English-speaking subjects from a parallel study. RESULTS: In comparison to the previously worn processor, statistically significantly superior performance (p<0.001) was observed at soft and conversational levels in quiet conditions for FMW in 15 subjects when using the W setting and in noisy conditions for the OLSA in 21 subjects when using the M setting (p<0.001). The ESPrit 3G was preferred by 86% of subjects (51/59). CONCLUSION: The ESPrit 3G for Nucleus 22 users has the potential to further improve speech understanding in quiet conditions at soft intensity levels and also in noisy conditions at conversational levels relative to the currently worn speech processor, the Spectra 22 or the ESPrit 22, for the majority of subjects. Subjectively, together with the improvement in sound quality, the majority of subjects also reported improved ease of use and wearer comfort.

Adolescent↗
PubMed1990

Does electrical stimulation of the crossed olivo-cochlear bundle produce movement of the organ of Corti?

Low-frequency microphonic waveforms have been recorded in the basal turn of the guinea pig cochlea with and without electrical stimulation of the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle. Stimulation of the COCB increased the amplitude of the microphonic waveforms as described previously, but did not alter the shape of the waveforms markedly. The changes observed with COCB stimulation are consistent with a reduction in the impedance of the basolateral wall of the outer hair cells by about 50%, and possibly a 20% increase in the vibration of the organ of Corti at low frequencies, but suggest little or no change in the operating point on the transfer curve relating deflection of the hair bundles to the receptor current through the hair cells. It therefore seems that if slow contraction of the outer hair cells occurs during acute efferent stimulation in vivo, then it produces only a small deflection of the outer hair cell stereocilia, equivalent to a transverse displacement of the organ of Corti of less than 1.5 nm.

Action Potentials↗
PubMed1976

Transtympanic electrocochleography in the diagnosis of retrocochlear tumours.

Transtympanic electrocochleography has been used as a diagnostic procedure in over 250 adult patients with sensorineural deafness. No complications have been encountered. Among these patients vestibulocochlear Schwannoma (acoustic neuroma) has been confirmed in 56 ears while 11 other ears have been found to be affected by other space-occupying lesions. As a result of our observations in these patients, we would like to propose that there are at least three separate criteria to be considered in reaching or strongly suspecting a diagnosis of such pathology. These are broadening of the action potential (loss of P1), observation of a clear microphonic response, and preservation of the action potential even when using stimulus intensities which are not audible in the patients' affected ears. The merits of each of these criteria are discussed and compared with other clinical and operative findings. With the electrocochleographic techniques now employed in searching for acoustic neuromas, false negative results are rare though false positive results are still obtained.

Acoustic Stimulation↗
PubMed2006

Clinical and genetic features in a Chinese pedigree with autosomal dominant auditory neuropathy.

BACKGROUND: A variety of processes and etiologies are thought to be involved in the pathophysiology of auditory neuropathy (AN). However, little is known about the clinical and molecular characteristics of hereditary AN. OBJECTIVE: To explore the clinical and genetic findings of a Chinese family with AN. METHODS: Seven patients in three consecutive generations of the pedigree were selected. Detailed history collection, physical examination, and audiological evaluations including pure-tone audiometry, acoustic immittance, auditory brainstem responses, cochlear microphonics, and evoked otoacoustic emissions, and mitochondrial DNA analysis were performed. RESULTS: All subjects involved are offspring of a female ancestor in the pedigree. In 6 of them, the hearing impairment started before the age of 9. Audiograms showed bilateral, symmetric, and profound deafness. Other audiological examinations revealed absent acoustic reflexes and auditory brainstem responses, and preserved evoked otoacoustic emissions and cochlear microphonics. One subject was characterized by normal audiological findings except high-frequency hearing loss with later onset. Hearing deterioration was found in 2 subjects who were followed for 26 months. Physical examination and mitochondrial DNA analysis yielded normal results. CONCLUSIONS: Clinical features in the pedigree are consistent with type II AN. Pedigree analysis and molecular findings indicate an autosomal dominant inheritance.

Adolescent↗
PubMed2001

Performance of an adaptive beamforming noise reduction scheme for hearing aid applications. I. Prediction of the signal-to-noise-ratio improvement.

Adaptive beamformers have been proposed as noise reduction schemes for conventional hearing aids and cochlear implants. A method to predict the amount of noise reduction that can be achieved by a two-microphone adaptive beamformer is presented. The prediction is based on a model of the acoustic environment in which the presence of one acoustic target-signal source and one acoustic noise source in a reverberant enclosure is assumed. The acoustic field is sampled using two omnidirectional microphones mounted close to the ears of a user. The model takes eleven different parameters into account, including reverberation time and size of the room, directionality of the acoustic sources, and design parameters of the beamformer itself, including length of the adaptive filter and delay in the target signal path. An approximation to predict the achievable signal-to-noise improvement based on the model is presented. Potential applications as well as limitations of the proposed prediction method are discussed and a FORTRAN subroutine to predict the achievable signal-to-noise improvement is provided. Experimental verification of the predictions is provided in a companion paper [J. Acoust. Soc. Am. 109, 1134 (2001)].

Acoustics↗
PubMed1983

Far-field cochlear microphonics in man and their relation to cochlear integrity.

Far-field cochlear microphonics (CM) in man have been measured as a function of frequency by phase-sensitive detection. CM amplitude, dispersion and input-output functions vary periodically with frequency and exhibit certain frequency windows, where responses are approximately frequency specific, in contrast to the commonly accepted model of basal turn CM generators as main sources. Pathological cochleae show abnormal amplitude and phase functions. The results offer new diagnostic possibilities, because haircell function can be evaluated by a routine non-invasive procedure down to the low frequency speech range.

Audiometry, Evoked Response↗
PubMedDate not supplied

Noninvasive chronic recording of auditory nerve potentials.

A system is described which allows repeated, noninvasive recording of auditory nerve responses in the cat to transient acoustic stimuli using a closed acoustic system. N1 responses to clicks are recorded from a stainless steel ring electrode at the end of a hollow earbar, the tapered end of which is made of insulating plastic. Acoustic stimuli are generated by a dynamic earphone coupled to the earbar. A calibrated probe microphone is also imcorporated into the earbar to measure sound pressure near the tympanic membrane. This allows better stimulus control than is available with free-field systems. To facilitate insertion of the earbar, meatoplasties were performed on all animals. Responses recorded with this system in anesthetized cats are described and compared with those recorded at the round window. Good repeatability of measurements is described for an animal population of 20 domestic cats over a period of several months. For some of these animals, response amplitude varied from one session to another, but response latency, especially for condensation clicks, was consistent. By comparing statistics of multiple measurement of both N1 amplitude and latency for rarefaction and condensation clicks, it is concluded that the N1 latency vs click-level function for condensation clicks provides the most reliable measure of the cat's auditory nerve function.

Animals↗
PubMedDate not supplied

[Sound sensations produced by electric stimulation of the structures of the middle ear and the tympanic chord].

Certain facts must be clearly understood before any attempt is made to analyse the sensations produced by electrical stimulation of the structures of the middle ear. Firstly, when the current passes from an electrode to the skin or to any polarised structure whatsoever, the point at which the electrode is applied and the skin behave like the two plates of a condenser microphone. Electrical vibrations are transformed into ordinary acoustic resonances which can travel through air or bone. These acoustic resonances are fairly pure in comparison with electrical vibrations, judged by the standards under investigation. If a continuous polarisation potential, which gives better distribution of the electrical charges, is added, the capacity of the microphone is increased and greater purity obtained. Consequently, the quality of sound heard in this way depends not only on the quality of this electro-physiological microphone but also on the quality of the internal ear. The acoustic effect produced in this way is called an electrophonic effect. Stevens, Jones and Flottorp described this. Therefore an internal ear which has lost the ability to hear high-pitched sound cannot hear them by means of this electrophonic effect any more than it can by ordinary auditory stimulation. Stimulation of the skin of the mastoid and of the external auditory meatus can be sensed by means of this electrophonic effect. Next, sensations recorded by means of direct stimulation of the acoustic nerve (DJOURNO and EYRIES) or by implantation of intra-cochlear electrodes (SIMMONS, DOYLE, MICHELSON) were studied. Sounds heard through stimulation of the structures of the middle ear should be analysed in the light of these findings and bearing in mind that very strong stimulation of the promontory or of the auditory meatus always causes an auditory sensation without frequency awareness due to global stimulation of the acoustic nerve (faciaestations appeared when experiments, the results of which are described, were carried out, although there is a possibility of episode vestibular irritation. These stimulations were in fact always very weak. Our results were analysed in relation to the quality of the internal ear: completely deaf, serious condition, internal ear normal. The impulses were provided by a direct current battery: these were square with a frequency of between 50 and 900 Hertz, a tension of 0 to 8 volts per 1/10 volt. The electrode was bipolar. The experiments were monitored from time to time by oscilloscope. Mention should be made of the technical and psychological precautions to be observed when stimulation of this kind is carried out if results of any value are to be obtained: a relaxed, sensible patient with whom one can communicate easily. Not much can be gathered from a person deaf in both ears. With the ear opened, the posterior part of the tympanum pulled forward, stimulation of the round window always results in production of a sound at a threshold of 0.5 to 2.5 volts.

Acoustic Stimulation↗
PubMed2002

Perinatal exposure to Aroclor 1254 impairs distortion product otoacoustic emissions (DPOAEs) in rats.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that are a potential health hazard to human and wildlife populations. Low-frequency auditory impairments have previously been documented in Aroclor 1254 (A 1254)-exposed rats, including elevated behavioral auditory thresholds and decreased amplitude and prolonged latency auditory evoked brain stem responses (ABRs). Furthermore, outer hair-cell loss on the basilar membrane of the cochlea has been documented, demonstrating that the cochlea is a target organ for PCB ototoxicity. The current experiment assessed the effects of A1254 on cochlear function by measuring distortion product otoacoustic emissions (DPOAEs). ABRs were measured to determine the effects of A1254 on the central nervous system auditory pathways. Pregnant Long-Evans rats received either 0 or 6 mg/kg A1254 (po) in corn oil from gestation day 6 to lactational day 21. The auditory function of male and female offspring was assessed at approximately 18 months of age. The rats were anesthetized and a probe-unit, consisting of 2 insert earphones and a microphone, was positioned in the ear canal. DPOAE amplitudes were reduced and thresholds increased in the A1254-exposed rats. The deficits were most pronounced at the lowest frequencies tested (2.1-3.2 kHz), but deficits were also observed at higher frequencies (3.7-8.6 kHz). Males and females were equally affected at the lower frequencies, but females were more impaired at the higher frequencies. In contrast, ABR latencies and amplitudes were not altered by A1254 exposure. These findings provide the first functional evidence supporting a cochlear site of damage in PCB-induced hearing loss.

Animals↗
PubMed1994

[Short-term reproducibility of acoustic oto-emissions induced by clicks in adults].

Otoacoustic emissions (OAE) are sounds emitted by the cochlea and recordable in the external ear canal by a miniature microphone. The OAE reflect the existence of an active mechanism within the cochlea. Development of the OAE has spurred much interest because they may used as a valid test for screening and monitoring cochlear changes. The OAE were recorded in 8 normal hearing subjects (15 ears) during nine test sessions under similar conditions. The aim of this work was to study the short-term variability in the amplitude of the emissions. Results of the study indicate that response levels are stable over time in the same ear therefore changes in the response level can be associated with changes in the cochlea.

Acoustic Stimulation↗
PubMed1994

Conventional and cross-correlation brain-stem auditory evoked responses in the white leghorn chick: rate manipulations.

Rate-dependent changes in the chick brain-stem auditory evoked response (BAER) using conventional averaging and a cross-correlation technique were investigated. Five 15- to 19-day-old white leghorn chicks were anesthetized with Chloropent. In each chick, the left ear was acoustically stimulated. Electrical pulses of 0.1-ms duration were shaped, attenuated, and passed through a current driver to an Etymotic ER-2 which was sealed in the ear canal. Electrical activity from stainless-steel electrodes was amplified, filtered (300-3000 Hz) and digitized at 20 kHz. Click levels included 70 and 90 dB peSPL. In each animal, conventional BAERs were obtained at rates ranging from 5 to 90 Hz. BAERs were also obtained using a cross-correlation technique involving pseudorandom pulse sequences called maximum length sequences (MLSs). The minimum time between pulses, called the minimum pulse interval (MPI), ranged from 0.5 to 6 ms. Two BAERs were obtained for each condition. Dependent variables included the latency and amplitude of the cochlear microphonic (CM), wave 2 and wave 3. BAERs were observed in all chicks, for all level by rate combinations for both conventional and MLS BAERs. There was no effect of click level or rate on the latency of the CM. The latency of waves 2 and 3 increased with decreasing click level and increasing rate. CM amplitude decreased with decreasing click level, but was not influenced by click rate for the 70 dB peSPL condition. For the 90 dB peSPL click, CM amplitude was uninfluenced by click rate for conventional averaging. For MLS BAERs, CM amplitude was similar to conventional averaging for longer MPIs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1990

[Acoustic oto-emissions. Clinical uses].

Otoemissions are acoustic signals emitted by the cochlea in response to a short acoustic stimulation (click) that may be recorded with a miniaturized microphone placed within the external auditory canal. They reflect the active mechanisms of the cochlea as they relate to the contractile properties of the outer hair cells, which determine the cochlear properties of sensitivity to and selectivity of frequencies. We have been studying for 5 years the clinical applications of otoemissions in over 500 patients. Otoemissions in 100% of normal ears may be recorded, and the detection threshold is generally 10 dB lower than the psycho-physiological threshold. In pathology, otoemissions present a practical interest in the following applications: objective investigation of perception hearing loss, early screening of cochlear disease consecutive to administration of ototoxic drugs, or sound-induced trauma; exploration of Meniere's disease; study of modifications induced by osmotic substances; diagnosis of retrocochlear disease; quick objective assessment of cochlear function in the newborn and the child.

Acoustic Stimulation↗