Showing papers in "Audiology and Neuro-otology in 1997"
TL;DR: The mismatch negativity (MMN), elicited by any discriminable change in a repetitive sound even when this sound is not attended to, provides a pre-perceptual physiological measure of the accuracy of the central sound representation in the human brain.
Abstract: The mismatch negativity (MMN), elicited by any discriminable change in a repetitive sound even when this sound is not attended to, provides a pre-perceptual physiological measure of the accuracy of the central sound representation in the human brain. This accuracy, which can be measured separately for the different features of the sound, determines the individual's sound discrimination accuracy in normal and various pathological conditions.
269 citations
TL;DR: Advances in dipole source localization and in auditory-evoked magnetic fields (AEMFs) have clarified the multiple, cortical origins of N1 and P2, promising tools for the neurophysiologic characterization of many disorders of central auditory processing and of speech and language development.
Abstract: Some properties and applications of the N1-P2 complex (100-200 ms latency) are reviewed. N1-P2 is currently the auditory-evoked potential (AEP) of choice for estimating the pure-tone audiogram in certain subjects for whom a frequency-specific, non-behavioural measure is required. It is accurate in passively cooperative and alert older children and adults. Although generally underutilized, it is an excellent tool for assessment of functional hearing loss, and in medicolegal and industrial injury compensation claimants. Successful use of N1-P2 requires substantial tester training and skill, as well as carefully designed and efficient measurement protocols. N1-P2 reflects conscious detection of any discrete change in any subjective dimension of the auditory environment. In principle, it could be used to measure almost any threshold of discriminable change, such as in pitch, loudness, quality and source location. It is established as a physiologic correlate of phenomena such as the masking level difference. Thus, N1-P2 may have many applications as an ObjectiveEo proxy for psychoacoustic measures that may be impractical in clinical subjects. Advances in dipole source localization and in auditory-evoked magnetic fields (AEMFs) have clarified the multiple, cortical origins of Nl and P2. These potentials are promising tools for the neuro-physiologic characterization of many disorders of central auditory processing and of speech and language development. They also may be useful in direct “functional imaging’ of specific brain regions. A wide variety of potential research and clinical applications of N1 and P2, and considerable value as part of an integrated, goal- directed AEP/AEMF measurement scheme, have yet to be fully realized.
222 citations
TL;DR: It is demonstrated that ABRs to tonal stimuli can be successfully recorded in most clinical environments and can provide reasonably accurate estimates of 500- to 4000-Hz pure-tone behavioral thresholds in infants, children and adults.
Abstract: This review paper briefly considers how stimulus, noise masking and recording parameters affect the frequency and place specificity of auditory brainstem responses (ABRs) to air- and bone-conducted stimuli. Issues concerning the use of clicks for ABR threshold estimates will first be presented, followed by results for tone-evoked ABR thresholds and how well they predict the pure-tone behavioral audiogram. Noise-masking options (e.g. high-pass noise, notched noise and white noise) to improve the frequency specificity of tone-evoked ABRs, which are now available on clinical ABR units, will also be discussed. The goal of this article is to demonstrate that ABRs to tonal stimuli can be successfully recorded in most clinical environments and can provide reasonably accurate estimates of 500- to 4000-Hz pure-tone behavioral thresholds in infants, children and adults. Specific parameters and protocols for obtaining frequency-specific ABR threshold responses are provided.
156 citations
TL;DR: Differences in ERPs of DLD and dyslexic children in comparison to controls may not reflect only maturational lag but also more fundamental processing deficiencies.
Abstract: This article reviews recent auditory event-related potential (ERP) studies of developmental language disorder (DLD) and dyslexia/reading disorder (RD). The possibility of using ERPs in searching for precursors of these disorders in the early development of infants at risk is also discussed. Differences in exogenous/sensory ERPs at the latency range of P1 and N1-P2 components have been reported between groups with DLD and RD and control groups. Latency differences between the groups may be related to a common timing deficit suggested by some researchers to be one of the possible underlying factors both in DLD and dyslexia. N1 amplitude group differences may be partly related to arousal/attentional factors and partly to the 'tuning' of the auditory sensory system. Mismatch negativity deviations in DLD children seem to indicate differences in sensory memory functions. Differences between the reviewed clinical groups and controls exist also in the endogenous P3 component, though less consistently in DLD children. In both clinical groups the P3 amplitudes are, in general, lower and the latencies longer compared to those in controls. These findings are discussed in terms of possible differences in higher cognitive functions that are not specific to modality. Altered hemispheric asymmetries in DLD and RD children, as compared to controls, are commonly found in many of the reviewed ERP components. Differences in ERPs of DLD and dyslexic children in comparison to controls may not reflect only maturational lag but also more fundamental processing deficiencies.
152 citations
TL;DR: Because the tub mutation causes degeneration of sensory cells in the ear and eye but has no other neurological effects, tubby mice hold unique promise for the study of human syndromic sensory loss.
Abstract: Mice homozygous for a defect of the tub ( rd5 ) gene exhibit cochlear and retinal degeneration combined with obesity, and resemble certain human autosomal recessive
55 citations
TL;DR: As effective as acetazolamide is in preventing attacks, prospective studies still have to prove whether it can prevent progressive ataxia in EA-2 or even improve chronic cerebellar deficits, since they can be easily treated and are often mislabeled.
Abstract: Episodic ataxia (EA) is a rare, disabling condition of autosomal dominant inheritance, but it is not a distinct clinical entity. Synonyms are familial periodic ataxia or hereditary paroxysmal cerebellar ataxia. Family members have a similar clinical syndrome; however, the syndrome varies considerably from family to family. At least two groups of disorders have been separated clinically: (1) episodic ataxia type 1 (EA-1), which manifests without vertigo and is associated with 'interictal' myokymia, and (2) episodic ataxia type 2 (EA-2), which often manifests with vertigo and is associated with 'interictal' nystagmus. EA-1 and EA-2 have been identified as channelopathies. EA-1 is due to different heterozygous missense point mutations in a voltage-gated (delayed rectifier) potassium channel gene (KCNA1/Kv1.1) on chromosome 12p13, whereas EA-2 is caused by mutations of the cerebral P/Q-type calcium channel alpha 1 subunit gene CACNL1A4 localized on chromosome 19p, which is highly expressed in the cerebellum. The diagnosis of EA-1 and EA-2 is important, since they can be easily treated and are often mislabeled. As effective as acetazolamide is in preventing attacks, prospective studies still have to prove whether it can prevent progressive ataxia in EA-2 or even improve chronic cerebellar deficits.
51 citations
TL;DR: Molecular biology will continue to provide important information for researchers of the auditory periphery because of the utility of the techniques and the diversity of expressed neurotransmitter receptors.
Abstract: Our present understanding of excitatory neurotransmission has expanded enormously in the last decade through the use of molecular biology. In the mammalian cochlea, the analysis of excitatory amino ac
39 citations
TL;DR: The genetic study of this five-generation family with hereditary hearing impairment associated with cochleosaccular dysplasia or degeneration will be helpful in identifying the genes which, when mutated, result in Scheibe degeneration.
Abstract: Cochleosaccular dysplasia or degeneration (Scheibe degeneration) is considered the most common cause of profound congenital hearing impairment, and accounts for approximately 70% of cases 2 with hereditary deafness. A five-generation family with hereditary hearing impairment associated with cochleosaccular degeneration has recently been identified. The diagnosis of classical Scheibe degeneration was based on histopathological findings in the temporal bones of the proband, a 61-year-old profoundly deaf male. Auditory structures in the brainstem of the proband were also studied. Twenty-two members of the family were contacted for surveys and blood samples. Of these, 6 males and 2 females have hearing impairment. Complete audiological evaluation was done on 12 family members, and prior audiologic records of the proband and affected family members were available for study. Affected family members suffer a mild bilateral high-frequency hearing loss during childhood and adolescence, and progress to moderate-to-profound deafness in the second and third decades of life. The family is suitable for linkage analysis and does not map to previously reported loci harboring autosomal dominant, nonsyndromic hereditary hearing impairment genes. The genetic study of this family will be helpful in identifying the genes which, when mutated, result in Scheibe degeneration.
38 citations
TL;DR: Administration of EGb 761 resulted in a statistically significant decrease of the behavioral manifestation of tinnitus for doses of 25, 50 and 100 mg/kg/ day.
Abstract: The effects of an extract from Ginkgo biloba , EGb 761, on tinnitus were tested using an animal model of tinnitus. Daily oral administration of EGb 761 in doses from 10 to 100 mg/ kg
35 citations
TL;DR: A role for extracellular ATP as a signalling molecule regulating electrochemical gradients and neurotransmission within the inner ear is supported by the extent of P2 receptor expression in this tissue, data which beg for intense functional study.
Abstract: The ability to identify the expression of the protein subunits which assemble to form ionotropic receptors for acetylcholine and extracellular adenosine 5'-triphosphate (ATP) in individual cells of the inner ear provides examples of the high resolution and exquisite sensitivity which molecular biology brings to the study of hearing and balance. The data from these studies provide both fine detail with respect to the classification of the elements involved and an overview of the sites of potential interaction of both extracellular and intracellular signalling pathways. The high sensitivity necessitates a molecular physiological approach when using these techniques so that these data on the site and extent of expression can be balanced against functional significance. With the demonstration of expression of the alpha 9 subunit of the nicotinic acetylcholine receptor in cochlear outer hair cells, molecular biology has provided an explanation for the unusual cholinergic receptor pharmacology of the olivocochlear efferent innervation which has confounded investigators for decades. In addition, a role for extracellular ATP as a signalling molecule regulating electrochemical gradients and neurotransmission within the inner ear is supported by the extent of P2 receptor expression in this tissue, data which beg for intense functional study.
34 citations
TL;DR: The purpose of this investigation was to study the effects of translabyrinthine acoustic neuroma surgery on tinnitus in a consecutive sample of patients operated on between 1988 and 1994 in Uppsala (Sweden).
Abstract: The purpose of this investigation was to study the effects of translabyrinthine acoustic neuroma surgery on tinnitus in a consecutive sample of patients operated on between 1988 and 1994 in Uppsala (S
TL;DR: An overview of current research where results gained by MMN testing in different patient groups were central to the interpretation of an assumed abnormality of processing or storing acoustic features.
Abstract: The mismatch negativity (MMN) is an event-related potential component that signifies neurophysiological processing of fine acoustic differences. The MMN indicates attention-independent change detection, reflects auditory sensory memory and provides a physiological measure of difference sensitivity. This paper will provide an overview of current research where results gained by MMN testing in different patient groups were central to the interpretation of an assumed abnormality of processing or storing acoustic features.
TL;DR: The review of current applications for cochlear potentials focuses primarily on the use of ECochG in the identification and treatment of Ménière's disease/endolymphatic hydrops (MD/ELH).
Abstract: The recording of cochlear and auditory nerve potentials in humans via Electrocochleography (ECochG) has emerged as a valuable tool for a variety of clinical applications. This review consolidates curr
TL;DR: Ten postlingually deafened adults in whom the electrophysical criteria for cochlear implant were fulfilled, except that they showed the following unfavorable middle ear lesions: otitis media with effusion, chronic perforative otitisMedia, cholesteatoma and previous radical ear operation.
Abstract: We report 10 postlingually deafened adults in whom the electrophysical criteria for cochlear implant were fulfilled, except that they showed the following unfavorable middle ear lesions: otitis media
TL;DR: The H2kbtsA58 transgenic mouse (Immortomouse) is described and its application to the production of conditionally immortalised cell lines from sensory epithelia within the mammalian inner ear is described.
Abstract: This review describes the H2kbtsA58 transgenic mouse (Immortomouse) and its application to the production of conditionally immortalised cell lines from sensory epithelia within the mammalian inner ear. Established cell lines should overcome many of the technical difficulties associated with experimental procedures in auditory and vestibular research. These include the limited amount of tissue available and the relatively complex and laborious dissection. Conditional immortalisation should also allow essential studies on the molecular and cellular mechanisms that govern both the differentiation of sensory cells and the development of sensory epithelia.
TL;DR: The results indicate that the vestibulotoxic effects of carboplatin occur quite rapidly and cause significant disruption of the mitochondria in hair cells and their afferent terminals.
Abstract: Carboplatin, a second-generation platinum drug used in the treatment of cancer, can damage the hair cells in the vestibular system; however, little is known about the time course of its vestibulotoxic effects. The present study examined the acute vestibulotoxic effects of carboplatin (50 mg/kg) in the chinchilla. The duration of the nystagmus response evoked by cold caloric stimulation was significantly reduced 6 h following carboplatin treatment and showed a maximum, permanent reduction of approximately 50% by 24 h after injection. Light-microscopic observations at 6 h subsequent to injection revealed swollen afferent dendrites beneath type-I hair cells and the appearance of small vacuoles within the type-I hair cells; these changes were most pronounced in the crista ampullaris of the semicircular canals compared to the maculae of the utricle and saccule. Many mitochondria were swollen and partially depleted of their membranous infoldings. The mitochondrial abnormalities tended to be somewhat more severe in the hair cells than in their afferent terminals. The structural abnormalities in the mitochondria were more severe at 24 h following injection resulting in the appearance of larger and more numerous vacuoles in the hair cells. By 3 days after injection, many type-I hair cells were filled with large vacuoles which often caused severe distortion of the nucleus and disruption of the plasma membrane. Small vacuoles were occasionally observed in type-II hair cells, mainly in the crista ampullaris. These results indicate that the vestibulotoxic effects of carboplatin occur quite rapidly and cause significant disruption of the mitochondria in hair cells and their afferent terminals.
TL;DR: Of the wide variety of recombinant retroviral vectors currently available, this review outlines which vectors are appropriate for particular applications and successful strategies for infecting the ear are reviewed.
Abstract: Retrovirus-mediated gene transfer holds great promise for elucidating key genes in the development and function of the inner ear. Retroviral vectors offer a number of advantages over other gene transfer methods including stable and efficient integration into the host genome, high levels of transcription and restriction of expression to a target area. Because of the wide variety of recombinant retroviral vectors currently available, this review outlines which vectors are appropriate for particular applications. Successful strategies for infecting the ear are reviewed and current drawbacks and future directions are discussed.
TL;DR: Viral mediated vectors and non-virally mediated vectors have been shown to efficiently transfer candidate genes into many different cell types, including hair cells, supporting cells, and spiral ganglion neurons and suggest that these vectors can be used effectively to study the role of specific genes during the development of the auditory system.
Abstract: The development of individual cells as hair cells and supporting cells is a key step during the embryonic formation of the auditory system. However, at present the factors that play a role in the commitment and differentiation of cells as hair cells and supporting cells have not been identified. Recent advances in molecular biological techniques have led to the identification of candidate genes that may be involved in hair cell and supporting cell development, however it has been difficult to determine the specific effects of these genes. The development of new methods for gene transfer into post-mitotic cells should provide powerful new techniques for examining the specific effects of candidate genes. Virally mediated vectors, such as adenovirus and herpes simplex virus, and non-virally mediated vectors, such as lipofectins and biolistics, have been shown to efficiently transfer candidate genes into many different cell types, including hair cells, supporting cells, and spiral ganglion neurons. In addition, studies in other developing systems have demonstrated that these techniques can be used to determine the effects of expression of candidate genes during the specification of individual cell phenotypes. These results suggest that these vectors can be used effectively to study the role of specific genes during the development of the auditory system.
TL;DR: Current knowledge of the expression of several transcription factors in the ear is reviewed and their implications for both development and homeostasis in the auditory organs are reviewed.
Abstract: In order to understand the molecular events underlying differentiation and development in the inner ear, we need to identify and characterize the molecular 'switches' involved in the regulation of gene expression in the system. The most important molecular regulators are represented by a family of proteins generically called transcription factors. This article reviews our current knowledge of the expression of several transcription factors in the ear and their implications for both development and homeostasis in the auditory organs.
TL;DR: A single-cell RT-PCR experiment can be combined with the electrophysiological characterization of an individual cell to lead to a better understanding of how functional properties of neurons are controlled by the expression of complex proteins.
Abstract: Many genes encoding proteins which are expressed in the auditory periphery have been identified in the last years. With single-cell reverse transcription-polymerase chain reaction (RT-PCR), the molecular analysis of gene expression can be done on the single-cell level. Furthermore a single-cell RT-PCR experiment can be combined with the electrophysiological characterization of an individual cell. The combination of these two methods will lead to a better understanding of how functional properties of neurons are controlled by the expression of complex proteins.
TL;DR: It is suggested that among patients with suspected PLF and signs of hydrops in TT ECoG, a dependence on the intrathoracic pressure reflected in the recordings may indicate a possible fistula.
Abstract: An objective method for the pre-operative diagnosis and the post-operative assessment of a presumed perilymphatic fistula (PLF) using transtympanic electrocochleography is presented. Three cases are reported in which the history of the disease and the symptoms strongly suggested the presence of a PLF. Pre-operative transtympanic electrocochleography (TT ECoG) recordings at rest showed changes similar to those of endolymphatic hydrops and signs of instability of the inner ear hydrodynamic system during raised intrathoracic pressure. Surgery revealed a visible leak in two of the three cases. Both windows were repaired in all the patients. All patients were relieved from their vestibular symptoms at the time when the post-operative TT ECoG was conducted 3-6 months later. The post-operative recordings were stable during raised intrathoracic pressure and the previously elevated summating potentials decreased which was interpreted as an objective indication of the recovery of the hydrodynamic system. However, later one of the patients again developed recurrent vertigo. Twenty patients with well-documented Meniere's disease were used as a control group. TT ECoG was conducted during raised intrathoracic pressure. The Meniere patients showed stable recordings. It is suggested that among patients with suspected PLF and signs of hydrops in TT ECoG, a dependence on the intrathoracic pressure reflected in the recordings may indicate a possible fistula.
TL;DR: A monaural conductive hearing loss was induced by interrupting the chain of the middle ear ossicles on the right side in gerbils of four different age groups, with deprivation being more effective in younger animals.
Abstract: A monaural conductive hearing loss was induced by interrupting the chain of the middle ear ossicles on the right side in gerbils of four different age groups (P12-14, P20-21, P42 and P84). The volumes of the cochlear nucleus subdivisions and the number of cells that expressed immunoreactivity for c-fos after noise stimulation were determined on the left and right side in the deprived animals, and in undeprived control animals when they reached the age of 6 months. The anteroventral cochlear nucleus on the deprived side was reduced in volume when the deprivation started before the age of 3 months. The other cochlear nucleus subdivisions showed no systematic age-dependent reductions. The expression of c-fos in the dorsal cochlear nucleus appeared more resistant to a hearing loss, with deprivation being more effective in younger animals. c-fos expression was also dramatically reduced in the ventral cochlear nucleus, regardless of age at the onset of hearing loss.
TL;DR: Mouse models have proved valuable tools in the analysis of human genetic disorders and the identification of the genes mutated in classical mouse mutants and theAnalysis of the phenotype of mutants following targeted gene disruption have provided some clarification of the development and functioning of the inner ear.
Abstract: Mouse models have proved valuable tools in the analysis of human genetic disorders. The identification of the genes mutated in classical mouse mutants and the analysis of the phenotype of mutants following targeted gene disruption have provided some clarification of the development and functioning of the inner ear. A number of these genes also play a role in human deafness. Analysis of mutations in both human and mouse deafness genes has identified a number of distinct phenomena that contribute to the observed phenotype.
TL;DR: The goal was to determine the limits of normal pressure sensitivity and to quantify the performance of the fistula test, and to measure nystagmus prior to and following pressurization of the external ear canal.
Abstract: In patients with perilymphatic fistula (PLF), nystagmus may sometimes be elicited by application of pressure to the external ear canal. The extent to which the normal population also exhibits such 'pressure sensitivity' is presently unknown. Our goal was to determine the limits of normal pressure sensitivity and to quantify the performance of the fistula test. Our subjects consisted of 13 normal controls and 7 patients with a history of pressure sensitivity who later underwent exploratory tympanotomy. We measured nystagmus prior to and following pressurization of the external ear canal. Pressure was applied manually over 60 s with a pneumatic otoscope bulb. In normal subjects, change in nystagmus between prepressure and postpressure tests ranged from -1.3 to 0.9%s. In patients, change in nystagmus greater than the 95th percentile limits of normal was not a reliable indication of PLF.
TL;DR: The results show that normal-hearing chinchillas have the same pattern of RM as humans, and that a noise exposure that produces TTSs also produces rapid and significant changes in RM.
Abstract: Remote masking (RM), the phenomenon whereby an intense high-frequency masking noise elevates thresholds for low-frequency signals, has been shown to be sensitive to various types of hearing loss in humans. We performed two experiments to evaluate the chinchilla as a model of RM and to examine changes in RM associated with temporary threshold shifts (TTSs) induced by low-frequency noise exposure. Thresholds for 0.5-, 1- and 2-kHz tones were measured in quiet, then in the presence of a narrow-band (300-Hz-wide) masking noise centered at 3 kHz. In Experiment I, effective masking was measured as a function of masker level, from 48 to 98 dB sound pressure level (SPL; referenced to 20 microPa), to determine threshold and rate of growth of RM in the chinchilla. In Experiment II, RM was measured before, during and after exposure to a low-frequency noise known to produce TTSs in chinchillas (i.e., a 0.5-kHz octave band noise at 90 dB SPL for 6 h/day for 10 days). The results show that normal-hearing chinchillas have the same pattern of RM as humans, and that a noise exposure that produces TTSs also produces rapid and significant changes in RM.
TL;DR: The topographic arrangement of vestibular nerve fibers innervating semicircular canal cristae of the chinchilla was studied using computer-aided video-microscopy and three-dimensional reconstruction and it was confirmed that large nerve fibers were more frequently found in the central bundles and small nerve fiber were more often found inThe peripheral bundles.
Abstract: The topographic arrangement of vestibular nerve fibers innervating semicircular canal cristae of the chinchilla was studied using computer-aided video-microscopy and three-dimensional reconstruction.
TL;DR: The degree of residual vestibular function seems to be one of the indicators influencing postoperative speech recognition by cochlear implant patients.
Abstract: Thirty-one postlingually deafened adults with 22-channel cochlear implants were evaluated preoperatively using vestibular function tests, the caloric test and stabilometry. The results of caloric response were classified into two diagnostic groups: normo- or hyporeflexia and areflexia. Stabilometric recordings were made using a computerized static posturographic platform. Between the two categories of caloric response, there was a significant difference in consonant recognition, but the recognition of vowels showed no significant difference. The results of the distance of body sway in stabilometry, but not of the area, correlated to the results of consonant recognition in speech perception tests. The degree of residual vestibular function seems to be one of the indicators influencing postoperative speech recognition by cochlear implant patients.
TL;DR: Northern blot analysis, the ribonuclease protection assay, semiquantitative PCR and differential display of mRNA are all techniques being used to greatly improve understanding of hair cell regeneration and may eventually provide the information necessary to induce regeneration in hearing-impaired humans.
Abstract: The sensory cells of the ear, the hair cells, are damaged by loud noise or certain types of drugs. In the bird cochlea, new hair cells are produced to replace those that are lost. Regeneration also occurs in the vestibular epithelia of birds, fish, and mammals but does not occur in the mammalian cochlea. In order to further our understanding of the regeneration process in the bird cochlea, we have begun to identify the genes that are involved. However, the small size of this organ has made it difficult to use traditional molecular biology methods to address these problems. Recently, many molecular techniques have been adapted for use with small amounts of tissue. Northern blot analysis, the ribonuclease protection assay, semiquantitative PCR and differential display of mRNA are all techniques that are being used to greatly improve our understanding of hair cell regeneration and may eventually provide the information necessary to induce regeneration in hearing-impaired humans.
TL;DR: The compound action potential (CAP) thresholds provide a reliable indicator for cochlear functional integrity during experimentation in birds as well as in mammals as discussed by the authors, but if experimental manipulati
Abstract: The compound action potential (CAP) thresholds provide a reliable indicator for cochlear functional integrity during experimentation in birds as well as in mammals. However, if experimental manipulati