Transitory evoked and distortion products of otoacoustic emissions in absent auditory evoked potentials

Transient click-evoked otoacoustic emissions (TEOAE) and distortion-product otoacoustic emissions (DPOAE) are produced by an active biomechanical process in the cochlea, presumably related to outer hair-cell activity. Although it is generally accepted that in most cases of hearing loss with absent auditory evoked potentials neither TEOAE nor DPOAE can be found, some cases with such a constellation have been described. Here we report another four cases of children with severe to profound hearing loss where we discovered reproducible TEOAE and DPAOE, whereas auditory evoked potentials were missing. TEOAE and DPOAE recordings in these cases indicate substantially preserved outer hair-cell function independent of profound pre-sensineural hearing loss. Since the incidence of children with preserved otoacoustic emissions together with impairment of synaptic or postsynaptic function of the first neuron is not known, the unconditioned use of TEOAE nor DPOAE as a screening instrument must be seriously questioned. Secondly, in conjunction with subjective audiometry and brain-stem-evoked potentials, emission recordings is an indispensable measurement prior to cochlear implantation and use of high-power hearing aids.     

Suitable fixation condition for rat liver using microwave irradiation and its application to the immunohistochemistry of glutamate dehydrogenase

In 50 patients auditory threshold and brain stem evoked potential studies were carried out before and after myelography. Due to the analysis of amplitudes and latencies of auditory brain stem measurements, significant functional disorders of the hearing organ and the auditory pathway could be demonstrated. In most of the patients these functional disorders were found to be subclinical, whereas 12 patients showed alterations extending from a subjectively slight hearing loss to an audiometrically objectified acute hearing loss depending on its intensity in each case. The reasons of these functional disorders could not be clarified. An open cochlear aqueduct through which perilymph enters the subarachnoidal space leading to a secondary endolymphatic hydrops can be considered as the cause in cases where manifest symptoms develop. The changes in brain stem audiometry can be additionally explained by changes in osmolality of the inner ear fluids which may lead to the development of an endolymphatic hydrops.     

Prognosis for survival and improvement in function in children with severe developmental disabilities

OBJECTIVE: To evaluate the feasibility and cost-effectiveness of using transient evoked otoacoustic emissions (TEOEs) to assess hearing in infants recovered from meningitis. METHODS: Recordings of TEOEs and visual reinforcement audiometry (VRA) were performed in a prospective study of 39 children aged 6 to 24 months recovering from a purulent meningitis. Patients with no TEOEs, or whose VRA findings were abnormal, were also tested by impedance audiometry and recording of auditory brain-stem responses (ABRs) after treatment of any secretory otitis media. Costs were compared with those of a previous protocol including VRA, impedance audiometry, and ABR for all children. RESULTS: A total of 29 children had TEOEs in both ears and normal VRA findings. Ten children lacked TEOEs in one or both ears; 9 of them had otitis media with effusion. Further examination by VRA and ABR led to the diagnosis of bilateral sensorineural hearing loss in 2.6% (1/39) of patients and unilateral sensorineural hearing loss in 7.7% (3/39) of patients. Cost analysis revealed that this protocol costs about half the previous one. CONCLUSION: Recording TEOEs appears to be a feasible and cost-effective hearing screening test for infants recovered from meningitis. If TEOEs are absent, impedance audiometry, ABR recordings, and audiometric evaluation techniques are needed to distinguish between conductive and sensorineural hearing loss and to assess hearing thresholds precisely.     

Otoacoustic emissions in full-term newborns at risk for hearing loss

Distortion product otoacoustic emissions (DPOEs) and click-evoked otoacoustic emissions (CEOEs) characteristics of the normal newborn population have been previously reported in the literature. There is little information about DPOE evaluations in the newborn population at risk for hearing loss. The authors now report the DPOE and/or CEOE data from six full-term subjects at risk for hearing loss or with highly suspected hearing loss. These subjects were less than 1 year of age and at risk for hearing loss secondary to a history of hereditary hearing loss, meningitis, hyperbilirubinemia, and ototoxic drug exposure. Audiometric evaluation included auditory brainstem responses (ABR), behavioral observation audiometry, and tympanometry. The CEOEs and DPOEs were found to be decreased or absent in the subjects with suspected hearing loss secondary to cochlear pathology; they were found to be normal in a subject with a suspected central hearing loss. This study's data suggest that otoacoustic emissions when combined with ABR can provide a frequency-specific evaluation of cochlear function and help determine the anatomic site of a pathologic lesion.     

Clinical application of transiently evoked otoacoustic emissions in screening for auditory dysfunction

Transiently evoked otoacoustic emissions (TEOAE) should be used clinically as an objective and noninvasive screening test for auditory dysfunction in children. The features of TEOAE measured by "ILO88" with non linear click stimuli are discussed. The following results were obtained: 1) The normal range of a power spectrum was determined using 42 adults with normal hearing and compared with data for sensorineural hearing disturbance. The power spectrum of TEOAE in adults with normal hearing sloped downward at high frequency and was the same for right and left ears in both males and females. For comparison with sensorineural hearing disturbance, a significant correlation between the audiogram and power spectrum of TEOAE was sought. 2) Patients with otitis media with effusion (109 ears in 67 children) were examined by audiometry, tympanometry and TEOAE. The hearing disturbance threshold of 45 cases with TEOAE was lower than that in cases with no TEOAE. In tympanometry, low intratympanic pressure was noted in the absence of TEOAE. 3) TEOAE and spontaneous otoacoustic emission were examined in 42 adults with normal hearing and 27 neonates using the same probe and level of stimuli to clarify differences in TEOAE according to age. The amplitude of TEOAE and the highest peak of the frequency component at 4kHz in neonates exceeded those of adults. The peak stimuli recorded with the intracanal probe in neonates was also larger than that of adults. Three out of 15 neonates had spontaneous otoacoustic emission and essentially the same proportion was noted in young adults.(ABSTRACT TRUNCATED AT 250 WORDS)     

Imaging of the vestibule

PURPOSE: State-of-the-art imaging of the normal and pathologic vestibule. METHODS AND MATERIAL: This study is based on the experience of three French imaging centers (Val de Grace, Bégin, and Saint-Antoine hospitals) working with 1- and 1.5-tesla magnetic resonance units and high-resolution computed tomography, and it includes a review of the literature. Computed tomography is performed with a high-resolution program, matrix 512 x 512, field of view 9.6 cm, joined 1-mm section, overlapped sections every 0.5 mm, axial and coronal sections, or reformatted images. High-resolution magnetic resonance imaging (matrix 512 x 384), field of view 18 cm, is used with fast T2-weighted sequences (sections 3 or 2 mm thick, constructive interference in steady state, T2-weighted gradient echo sequence three-dimensional Fourier transformation). A joined section of 0.7 mm in any direction is obtained if necessary. Superimposition of computed tomography and magnetic resonance imaging with a stereotactic technique by identification of identical anatomic points is sometimes used. RESULTS: We review the interest and place of computed tomography and magnetic resonance imaging in the diseases of the labyrinth and internal auditory canal related to abnormal vestibular functions: inflammatory labyrinthitis, vestibular hemorrhages, sclerosing and ossifying labyrinthitis, traumatism, malformations, perilymphatic fistulas, otosclerosis, tumors, cochleovestibular neuritis, and hydrops of the endolymphatic system.     

Cytochrome P450 enzyme activities in the Australian brushtail possum trichosurus vulpesula: a comparison with the rat, rabbit, sheep and chicken

630 neonates with risk factors of perinatal hearing impairment were screened of hearing loss by means of registration of transient otoacoustic emissions before discharge from the newborn nursery. Neonates were screened additionally by means of brainstem evoked response audiometry, if they had bilateral negative emissions. 810 healthy neonates were screened as control group. The investigations were carried out in incubator after the feeding of neonates. The prevalence of a bilateral negative cochlear response was 5.2% in the risk babies and 1.7% in healthy neonates. Neonates are high risk patients for hearing loss if they show craniofacial anomalies including alcohol embryofetopathy, connatal infections, or very low birth weight babies with additional risk factors. The pedaudiological control investigations of the babies with a negative bilateral cochlear response delivered in the risk group 15 cases (2.4%) with an important hearing impairment and in the healthy neonates 2 cases (0.25%) respectively. Prevalence and importance of perinatal hearing impairment explains the necessity of detection in the neonatal period.     

Recording otoacoustic emissions in expert evaluation of chronic noise-induced hearing loss

In order to assess occupational hearing loss, damage to outer hair cell function must be demonstrated. Measurements of transiently evoked otoacoustic emissions (TEOAE) and distortion products (DPOAE) allow clinicians to investigate objectively the cochlear amplification process. In this prospective study, 50 persons with suspected occupational hearing losses were tested with pure-tone and speech audiometry. Additionally, TEOAE and DPAOE were determined. Significant linear correlations were observed when comparing hearing thresholds and speech discriminations with evoked emissions. Three groups were formed based on the OAE results: group A, TEOAE- and DPOAE-positive; group B, TEOAE-negative, DPOAE positive; group C, TEOAE- and DPOAE-negative. The groups were compared with regard to the weighted and simple discrimination scores and percentage of hearing loss computed according to the Boenninghaus-R?ser tables. Analysis of variance showed significant differences in hearing losses among the three groups, allowing an objective statement to be made about the degree of work compromise: group A, < 10%; group B, 10-15% group C, > or = 20%.     

Subjective assessment of allergy relief following group hypnosis and self-hypnosis: a preliminary study

Distortion Product Otoacoustic Emissions (DPOEs) are otoacoustic emissions evoked by two pure equilevel tones (f1, f2) called primaries and are believed to provide frequency-specific information regarding cochlear function. We recorded DPOEs at 2f1-f2 frequency with a constant frequency ration (f2/f1 = 1.22) in 8 normal hearing subjects (16 ears, mean age 28 +/- 1.5) to establish the characteristics of these emissions in the adult population. DPOEs were measured at the following F2 frequencies and respective fp geometric mean frequencies: 696/632, 1001/904, 1501/1360, 2002/1809, 3003/2714, 4004/3626, 5005/4531 e 6006/5435 Hz. Detailed testing included the recording of DPOE "audiograms" and input-output functions depicting the relationship of the amplitudes of DPOE to primary-tone levels ranging from 25 to 70 dB SPL in 5 dB steps. The present findings are in good agreement with investigations based on evoked otoacoustic emissions published by other researchers. The average DPOE "audiograms" demonstrated a low-frequency maximum at 1501 Hz (f2)/1360 (fp) and a high-frequency peak at 5005 Hz (f2)/4531 (fp). The two maximum regions were separated by a minimum around 3003 Hz (f2)/2714 (fp). This study confirms the feasibility of DPOE measurements among adults and provide a normal baseline for this age group. DPOEs could be useful, in association with evoked otoacoustic emissions and with auditory brainstem responses, in obtaining a precise evaluation of the peripheral auditory system.     

Laboratory experience with experimental endolymphatic hydrops

Experimental endolymphatic hydrops refers to the creation of hydrops in the experimental animal and represents a histologic correlate for Meniere's disease. Details of the surgical means to create this condition in guinea pigs are provided. Alterations in endolymph fluid composition and relative endolymph pressure occur with hydrops. Deterioration in auditory and vestibular function secondary to hydrops can develop.     

Analysis of evoked otoacoustic emissions in patients with high frequency cochlear hearing loss

Evoked otoacoustic emissions (EOAE) and auditory brainstem evoked response (ABR) were tested in patients with high frequency cochlear hearing loss and subjects with normal hearing. Results showed that: 1. In the normal group, the main component of EOAE varied between 0.5-5kHz. 2. There was a close correlation between the pure-tone audiogram figure and EOAE spectrum. 3. The I/O function curves of EOAE displayed non-linear characteristics and a trend of saturation with higher stimulus levels in the normal group. In the patient group the growth rates of EOAE and ABR were remarkably higher than those in the normal group with high stimulus levels. It suggests that the abnormal EOAE are probably relevant to the recruitment phenomenon in cochlear hearing loss.     

Contralateral suppression of transiently evoked otoacoustic emissions and neuro-otology

Transiently evoked otoacoustic emissions can be suppressed with simultaneous contralateral sound stimulation. This is considered to be effected via the efferent pathway from the superior olivary complex (SOC) to the contralateral cochlea. This study examined this effect in patients with extrinsic and intrinsic lesions of the brainstem which may affect the efferent pathway either within the vestibular nerve which carries the efferent bundle to the cochlea or within the brainstem at the level of the SOC. Suppression is reduced or absent in these patients and the site and size of the lesion determines whether the suppression is affected unilaterally or bilaterally. Lesions affecting the auditory afferent pathway without significant alteration in hearing appear to affect the efferent pathway too.     

Presence of tinnitus indicated by variable spontaneous otoacoustic emissions

Spontaneous otoacoustic emissions (SOAE) have been widely studied in normal subjects, and there is evidence of their high frequency stability in repeated recordings. A study to determine the frequency stability of SOAE in 53 of 100 consecutive patients, who presented with tinnitus and in whom SOAE were recordable, was undertaken. Patients were divided into five aetiologically homogeneous subgroups: (i) those with normal hearing and no identified pathology, (ii) those with sensorineural hearing loss of unknown origin, (iii) those with normal hearing, but complaining of tinnitus related to head injury, (iv) those with endolymphatic hydrops, and (v) those with noise exposure. The control group consisted of 20 subjects, selected on the basis of recordable SOAE from 38 volunteers with normal hearing and no tinnitus. The prevalence of SOAE and their inter-session frequency stability (reproducibility and relative frequency shift) were analysed. In contrast to the controls, the tinnitus group had significantly increased frequency variability of SOAE (lower reproducibility and increased relative frequency shift). The prevalence of subjects with SOAE was not notably different between the controls and subjects with tinnitus, if the tinnitus group was considered in toto, but a striking 100% prevalence of bilaterally present SOAE was observed in the tinnitus subgroup with head injury.     

Establishing a link between cultural evolution and sexually transmitted diseases

Measurement results of click evoked otoacoustic emissions (EOAE) and distortion products otoacoustic emissions (DPOAE) in a case of sensorineural hearing loss in a case of sensorineural hearing loss in a patient with a history of oticus zoster with nerve VII palsy are presented. Feasibility of using otoacoustic emissions measurements for hearing loss type identification is discussed.     

Potential effects of managed care organizations in rural communities: a framework

OBJECTIVE: To define mechanisms accounting for transient deafness in three children (two siblings, ages 3 and 6, and an unrelated child, age 15) when they become febrile. DESIGN: Audiometric tests (pure-tone audiometry, speech and sentence comprehension), tympanometry, middle ear muscle reflex thresholds, otoacoustic emissions (OAEs), and electrophysiological methods (auditory brain stem responses [ABRs], sensory evoked potentials, peripheral nerve conduction velocities) were used to test the children when they were afebrile and febrile. RESULTS: ABRs, when afebrile, were abnormal with a profound delay of the IV-V and absence of waves I-III. The ABR in one of the children, tested when febrile, showed no ABR components. Measures of cochlear receptor function using OAEs were normal in both febrile and afebrile states. Cochlear microphonic potentials were present in the three children, and a summating potential was likely present in two. When afebrile, there was a mild threshold elevation for all frequencies in the 15-yr-old and a mild elevation of thresholds for just low frequencies in the two siblings. Speech comprehension in quiet was normal but impaired in noise. One of the siblings tested when febrile had a profound elevation (>80 dB) of pure-tone thresholds and speech comprehension was absent. Acoustic reflexes subserving middle ear muscles and olivocochlear bundle were absent when febrile and when afebrile. No other peripheral or cranial nerve abnormalities were found in any of the children. Sensory nerve action potentials from median nerve in one of the children showed no abnormalities on warming of the hand to 39 degrees C. CONCLUSION: These children have an auditory neuropathy manifested by a disorder of auditory nerve function in the presence of normal cochlear outer hair cell functions. They develop a conduction block of the auditory nerves when their core body temperature rises due, most likely, to a demyelinating disorder of the auditory nerve. The auditory neuropathy in the two affected siblings is likely to be inherited as a recessive disorder.     

IL-15 induces the release of soluble IL-2Ralpha from human peripheral blood mononuclear cells

The present study was designed to investigate the applicability of transient evoked otoacoustic emissions (TEOAEs) as a method of screening for hearing losses among recruits attending obligatory military service. TEOAEs, tympanometry and puretone audiometry were recorded in 95 male recruits. Sixty-one recruits were tested after a 2-month period of gunfire exposure in order to document any permanent change in cochlear function. Screening by pure-tone audiometry showed an unexpectedly high prevalence of hearing losses > 20 dBHL, probably due to technical reasons. Thresholds were corrected using lower thresholds obtained at the end of service or by ENT specialists. The accuracy with which normal and impaired ears could be identified with TEOAEs analysed in frequency bands was determined by decision theory. Impairment was defined as mean hearing thresholds > or = 30 dBHL averaged from three neighbouring frequencies. Adequate accuracy was obtained in the middle frequencies. Further improvement of the technique is needed before it can be deemed suitable for detecting hearing losses at low and high frequencies. TEOAEs are quicker to measure and offer greater objectivity than pure-tone audiometry. A small decrease in TEOAE level was found after the training period. The TEOAEs were highly repeatable and had a higher sensitivity than pure-tone audiometry to detection of small changes in cochlear function under conditions normally found when testing recruits.     

Tumor necrosis factor and AIDS

A guinea pig model with surgically induced endolymphatic hydrops of the inner ear has been developed and studied over the past thirty years. The aim of such studies is to obtain insight into physiological processes associated with endolymphatic hydrops in man and in particular in Menière's disease where endolymphatic hydrops is systematically encountered at post-mortem examination of the temporal bones. The present review attempts to draw together the data pertaining to functional modifications of inner ear function in the animal model. For simplicity the data are categorised under five main titles: electrochemical modifications, electrophysiological modifications, pressure and hydrops, sensitivity to other insults and vestibular dysfunction. One of the most striking observations that can be made is that the data originating from different authors are very variable. There is, however, some evidence suggesting that the evolution of the auditory dysfunction could be considered as consisting of a series of different phases. This kind of information could serve as a basic framework for future research on the animal model.     

A new class of pyrrolidin-2-ones: synthesis and pharmacological study. II

OBJECTIVE: The measurements of transient evoked otoacoustic emissions and distortion-product otoacoustic emissions are being used increasingly, both as an objective hearing test clinically, and as a research tool to investigate the micromechanical aspects of cochlear function. We hypothesized that localized damage in the apical or middle cochlear turns may have an influence on the micromechanics and the function of adjacent, apparently normal cochlea. For that purpose, we used an animal model of localized apical and middle-turn cochlear lesions. METHOD: Extent of damage was assessed by scanning electron microscopy and the function of the damaged cochlea by change in the otoacoustic emission (OAE) levels. RESULTS: We found that localized damage to the apical or middle turn may be accompanied by an increase in OAE measured from adjacent apparently normal cochlea. CONCLUSION: Explanations to this phenomenon are suggested, and possible clinical associations such as to Meniere's disease and to sudden hearing loss are reviewed.     

Hearing impairment in two boys with Cornelia de Lange syndrome

We analyzed brainstem auditory evoked potentials in 2 boys with Cornelia de Lange syndrome. One patient showed no responses with 100 dB hearing level (HL) stimuli. The other showed a normal latency of wave I, a normal I-V interpeak latency with 80 dB HL stimuli, and an elevated threshold of wave V (40 dB HL). It is likely that these abnormal findings reflect the presence of sensorineural hearing impairment.     

Hearing loss from hemodialysis

A 47-year-old man with normal hearing had chronic progressive renal failure. He experienced hearing loss in additive increments with peritoneal dialysis and hemodialysis, until he was profoundly deaf in both ears. Postmortem studies showed collapse of the endolymphatic system and edema and atrophy of most of the specialized cell types of the auditory and vestibular sense organs. It is our interpretation that the alterations were caused by osmotic disequilibrium associated with hemodialysis.