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At least 1,423 records · Page 79Linked to original sources
PubMed2003

Utility of area curve ratio electrocochleography in early Meniere disease.

BACKGROUND: Electrocochleography (ECochG) is useful in supporting the diagnosis of Meniere disease (MD). Possible MD (early disease as defined by the 1995 American Academy of Otolaryngology-Head and Neck Surgery Committee on Hearing and Equilibrium) is a readily treatable form of MD. OBJECTIVES: To identify whether ECochG summating potential/action potential (SP/AP) area curve measures are more sensitive than conventional SP/AP amplitude ratios in detecting possible MD. PATIENTS AND METHODS: A retrospective chart review of a 3-year period (1997-2000) was conducted. All charts of patients diagnosed as having MD who had undergone tympanic ECochG were examined to identify those with possible MD. Exclusion criteria were incomplete workup, ECochG performed using a prior system, cochlear microphonic spike obscuring ratio measurements, and prior otologic surgery. A control group of patients with normal SP/AP ratios and ECochG data were identified. SP/AP amplitude and area curve ratios for both groups were measured. RESULTS: Of 138 patients with MD reviewed, 20 (14%) had possible MD, and 8 passed exclusion criteria. An audiologist blinded to patients' diagnoses performed all measurements. The upper limit of normal for SP/AP amplitude and area curve ratios from the control group of ears (n = 13) (alpha =.05) were similar to previously published results. Of the 8 patients with possible MD, 4 had an abnormal SP/AP amplitude ratio, and 7 had an abnormal SP/AP area curve ratio; the difference between groups was statistically significant (P =.03, chi2). CONCLUSIONS: The SP/AP area curve ratio significantly improves ECochG diagnostic sensitivity in possible MD. This ECochG refinement will allow earlier intervention to preserve inner ear function in MD.

Action Potentials↗
PubMed2000

Vestibular function in auditory neuropathy.

Auditory neuropathy is characterized by mild-to-moderate pure-tone hearing loss, poor speech discrimination out of proportion with this loss, absent or abnormal auditory brainstem responses and normal outer hair cell function as measured by otoacoustic emissions and cochlear microphonics. We followed three patients in our clinic whom we classified as auditory neuropathy patients. These patients also complained of balance disorders and we report our auditory and vestibular system analyses of these patients. The data presented herein include results of audiometric tests (serial pure-tone audiometry and speech discrimination tests), otoacoustic emissions, auditory-evoked brainstem responses and vestibular function tests (clinical tests of balance, electronystagmography, damped rotation tests and vestibular-evoked myogenic potentials). In all patients, pure-tone audiometry revealed mild-to-moderate sensorineural hearing loss, markedly poor speech discrimination scores and absent auditory-evoked brainstem responses, all in the presence of normal otoacoustic emissions. Balance tests (caloric tests and damped rotation test) were abnormal. Saccades, smooth pursuit eye movements and optokinetic nystagmus were normal in all patients. Neurological and motor system evaluations were normal in all patients. These three auditory neuropathy patients manifest a disorder of cochlear nerve function in the presence of normal outer hair cell activity. They additionally manifest a disorder of the vestibular nerve and its end organs. We conclude that, in patients with isolated auditory neuropathy, the vestibular branch of the VIIIth cranial nerve and its innervated structures may also be affected. We suggest the use of the term "cochlear neuropathy" to characterize those patients with involvement of only the auditory branch of the VIIIth cranial nerve and its innervation.

Aged↗
PubMed1987

Human short-latency auditory responses obtained by cross-correlation.

Short-latency auditory responses were obtained by cross-correlation of continuous, pseudorandom noise stimuli with averaged scalp potentials from adults with normal hearing. Responses were recorded for spectrum levels of 14-74 dB for noise bandwidths from 800 to 6000 Hz. At the lowest intensity level of broadband noise, all 10 subjects showed replicable cross-correlation functions (CCFs), which were characterized by prominent positive peaks at delays (latencies) of 5-7 msec. Male subjects exhibited longer delays than females. Delay (latency) increased with decreasing stimulus intensity. Very early responses (less than 2 msec) attributable to cochlear microphonic, which were prominent in earlier work on guinea pigs, were not well seen in these human data. CCFs for responses to band-limited stimuli and off-line derivation of band-limited CCFs for responses evoked by broadband stimuli both showed that this technique is most sensitive to frequency-following behavior at low frequencies (less than 800 Hz). However, definite phase-locked responses to even the highest passband (3100-6200 Hz) were seen. These results support the use of the CCF technique as an efficient method of frequency-specific assessment of the auditory system.

Adult↗
PubMed1975

Non-surgical recording of auditory pathway function in cats.

The techniques are described for serial, non-surgical recording of the cochlear microphonic (CM), the electrocochleogram (ECoG) and the averaged electroencephalic response (AER) in cats. The early post-natal period has been systematically studied in a breeding strain of hereditarily deaf white cats, and illustrative examples are presented from animals with histologically normal chochleae, and also from ears with confirmed chochleosaccular degeneration. Transitory potentials have been recorded with the CM and ECoG procedures from some of the latter.

Age Factors↗
PubMed1972

Cochlear inner and outer hair cells: functional differences.

The cochlear microphonic response was measured with differential electrodes from the first and third cochlear turns of normal guinea pigs and those treated with the ototoxic drug kanamycin. Histological controls showed that the outer hair cells in treated animals were missing over the basal half of the damaged cochleas, while the inner hair cells were intact. Measurements are consistent with the hypothesis that the potentials produced by inner hair cells are proportional to the velocity of the basilar membrane, whereas potentials generated by outer hair cells (which dominate the response of normal cochleas) are proportional displacement of the basilar membrane.

Animals↗
PubMed1978

Auditory responses in cats produced by pulsed ultrasound.

Auditory-nerve responses and cochlear microphonics are produced in cats by pulsed 5-MHz ultrasonic energy from a transducer placed against the dura mater. The pulses must be relatively intense (approximately 30 W/cm2) to produce a response, but can be sufficiently brief (less than 70 microsecond) that the brain tissue is not observably heated. The cats apparently respond to radiation pressure transients accompanying the absorption of the ultrasound in the brain tissue. Both the amplitude and latency of the N1 neural responses to the ultrasound can be matched to those produced by relatively weak tone pips or clicks from an external source. The cochlear microphonic (CM) produced by a pulse shows a prominent ringing at 5-10 kHz in different cats; the amplitued of the N1 response exhibits broad maximum, for constant amplitude pulses, a pulse widths of 20-60 microsecond. This variation of N1 response amplitude with pulse width is similar to that of a high-pass filter with a cutoff frequency at the dominent frequency of the CM, which is tentatively identified with a ringing frequency of the skull.

Acoustic Stimulation↗
PubMed2001

Electrophysiological measures of auditory function in the neurofilament-deficient mutant quail (Quv).

Auditory pathway electrophysiological studies were performed on the mutant quail 'Quv'. This mutation is known to result in neurofilament deficiencies of both the peripheral and central nervous systems. Auditory evoked brainstem responses (ABRs), electrocochleograms (EcochGs) and middle latency responses (MLRs) were evaluated. ABRs in Quv quails demonstrated markedly altered waveforms exhibiting longer latencies, absence of the later peaks and lower amplitudes. The EcochG showed normal cochlear microphonics with no obvious abnormalities in amplitude or latency and normal latencies for peak N1. Quv quails had a mild threshold elevation with a normal latency for the first peak of the ABR (P1). The Quv MLRs showed no significant differences in amplitude but they revealed a latency prolongation for peaks N0, Pa and Na relative to the controls. We have discovered abnormal findings of auditory evoked potentials in the neurofilament-deficient quail (Quv). We suggest that the smaller axonal size and axonal hypotrophy due to altered neurofilament expression underlies these abnormal auditory evoked potential responses.

Acoustic Stimulation↗
PubMed1981

Frequency-following potentials in man by lock-in technique.

Frequency-following responses (FFR) from continuous tone stimulation were investigated by lock-in analysis. The technique is superior to conventional tone-burst stimulation, because it allows continuous registration of the response parameters with sweeping frequency. The scalp recorded FFR consists of at least two components separable from each other by their phase/frequency relationship. The microphonic component that dominates in ipsilateral records shows latencies of about 0.5 msec with negligible dispersion and must therefore originate in the basal cochlear turn. The neural component exhibits considerable dispersion, reflecting the travelling wave delay up to the region of best frequency. These long cochlear time delays are consistent with an apical FFR origin, and brain stem sources of the continuous tone response appear to be questionable. The present FFR analysis technique opens up a very direct and comprehensive way to assess the integrity of the entire inner ear for high frequency basal and low frequency apical cochlear regions as well.

Acoustic Stimulation↗
PubMed1982

Group delay measurements from spiral ganglion cells in the guinea pig cochlea.

Measurements of group delay were made extracellularly from spiral ganglion cells in the basal turn of the guinea pig cochlea, using sinusoidally amplitude modulated tones, with constant modulating frequency and modulation depth at the microphone input. Threshold cochlear tuning was accompanied by a frequency dependent group delay, with relative peak proportional to Q10. For sensitive units with steep intensity functions, the group delay decreased with increasing sound pressure level above threshold, without a significant change of Q10.

Animals↗
PubMed1998

Auditory neuropathy in childhood.

OBJECTIVES: Auditory neuropathy is a recently described disorder in which patients demonstrate hearing loss for pure tones, impaired word discrimination out of proportion to pure tone loss, absent or abnormal auditory brainstem responses, and normal outer hair cell function as measured by otoacoustic emissions and cochlear microphonics. We have identified eight pediatric patients having hearing deficits that are most likely due to a neuropathy of the eighth nerve. In this study, the results of audiologic testing performed with these eight children are described. STUDY DESIGN: Retrospective review of audiologic findings in eight children with auditory neuropathy. METHODS: Each subject was tested with pure tone and speech audiologic testing, auditory brainstem response, and click-evoked otoacoustic emissions. Results of these tests were tabulated and summarized. RESULTS: Pure tone audiologic testing revealed five children with upsloping sensorineural hearing loss, two with high frequency loss, and one with a mild, flat configuration. Six children demonstrated poor word discrimination scores, and the other two had fair to good word discrimination. All eight subjects had normal distortion product and transient otoacoustic emissions. All eight children demonstrated absent or marked abnormalities of brainstem auditory evoked potentials. These findings suggest that while cochlear outer hair cell function is normal, the lesion is located at the eighth nerve. CONCLUSIONS: Recent advances in otoacoustic emissions testing permit differentiation of neural deafness from sensory deafness. This paper describes the clinical presentation and audiologic findings in pediatric auditory neuropathy, as well as the recommended management of these patients. Otolaryngologists should be aware of this disorder and implications for its management, which differs from treatment of sensorineural hearing loss.

Adolescent↗
PubMed1988

A new rapid component in the cochlear response to brief electrical efferent stimulation: CM and otoacoustic observations.

The onset and time course of cochlear response changes induced by brief electrical stimulation of medial fibres of the OCB have been studied in detail in guinea pig. Changes in both cochlear microphonic and otoacoustic responses begin within 10 ms of electrical excitation. The sensitive differential technique employed has allowed the use of very short and weak electrical stimulations. The effects of induced levels of activity close to those normally present are reported. After transient electrical excitation (a single 100 microseconds, 20 mu amp shock), changes in the cochlear microphonic response reached a maximum around 20 ms. Thereafter the perturbation decayed initially with a time constant between 30 and 45 ms, then more slowly with a time constant greater than 100 ms. For more intense but still brief excitation the initial response decay was even more rapid often resulting in a bimodal decay pattern - a discrete 'burst' and a 'slow tail'. Otoacoustic data was similar. Only the slow tail component corresponds to previously reported effects and we suggest that it may be associated with overstimulation of the efferent system.

Acoustic Stimulation↗
PubMed1993

Intermodulation distortion (F2-F1) in inner hair cell and basilar membrane responses.

Round window (RW) recordings in guinea pigs show a large response at the frequency of the quadratic difference tone (QDT) at F2-F1 for high-frequency (> 8 kHz) tone pairs. The magnitude of the RW response is dependent on frequency and level of the primaries. The QDT cochlear microphonic produced is largest for primaries with a frequency separation of approximately 900 Hz. Its source is probably the local activity of hair cells in basal cochlear locations where the high-frequency tones interact. QDT measurements from locations inside the organ of Corti show that the magnitude of the QDT is largest in the inner hair cell (IHC) region and monotonically increases as the difference in the frequency of the primaries decreases. Measured as IHC intracellular ac receptor potential, the QDT appears to be the result of a mechanical stimulus to the cell rather than as an inherent property of the nonlinear transduction in the IHC. However, QDT of the same form is not evident in the velocity responses of the basilar membrane. These results suggest that the outer hair cells (OHC) produce a strong quadratic distortion product mechanical force to stimulate inner hair cells. This mechanical drive may not be present, or is a weak component, in basilar membrane motion.

Acoustic Stimulation↗
PubMed1974

Noise-induced reduction of inner-ear microphonic response: dependence on body temperature.

The rate of reduction of chinchilla cochlear microphonic response with exposure to steady noise is less at lower body temperatures and greater at higher body temperatures. Before exposure to noise, this auditory response is invariant within the range of temperatures employed. The mechanism of reduction of cochlear response appears to involve processes sensitive to body temperature.

Animals↗
PubMed1994

Improvement in auditory function following pentazocine suggests a role for dynorphins in auditory sensitivity.

The pharmacologic specificity of potentially beneficial drug effects on the auditory system were investigated. Changes in auditory sensitivity were evaluated in chinchillas following the infusion of an opioid narcotic. This drug (pentazocine) mimics endogenous opioid peptides (dynorphins), postulated to be chemical neurotransmitters (or neuromodulators) within the mammalian cochlea. In this study, two pentazocine enantiomers were investigated over a range of stimulus intensities. Significant baseline-relative changes in compound action potential (CAP) amplitudes were observed following intravenous administration of the kappa-opioid agonist (-)pentazocine (8 mg/kg). The sigma-receptor drug agonist (+)pentazocine (8 mg/kg) produced no measurable auditory effects. The magnitude of the (-)pentazocine effects were inversely related to stimulus intensity, up to 10 dB above threshold (i.e., 10 dB SL). Consistent with the observed amplitude doubling, auditory sensitivity was also improved an average 5-7 dB sound pressure level (SPL) following the administration of (-)pentazocine, while CAP response latencies and cochlear microphonic (CM) amplitudes remained unchanged. Results indicate stereospecific kappa-receptor mediated actions of pentazocine at the auditory nerve, and suggest an auditory role for neuroactive dynorphin peptides contained within the lateral efferent olivocochlear neurons.

Animals↗
PubMed1996

Naloxone blockade of (-)pentazocine-induced changes in auditory function.

OBJECTIVE: In a previous report, we found that intravenous (i.v.) (-)pentazocine improved auditory sensitivity and significantly altered compound action potential (CAP) amplitudes. Its sigma (sigma)-receptor-selective optical isomer (+)pentazocine administered at the same dose was without effect, suggesting that the observed auditory neural effects might be mediated by an opioid receptor. To directly test this hypothesis, in the present investigation we attempted to antagonize the auditory neural effects of (-)pentazocine using the pure, nonspecific drug antagonist naloxone. DESIGN: In 25 normal-hearing, male, pigmented chinchillas, amplitude and latency changes in the click-evoked auditory nerve CAP (N1) and cochlear microphonic (CM) were tracked at six stimulus intensities during a baseline period and after the postbaseline administration of the opioid drug agonist (-)pentazocine (16 mg/kg; i.v.). In separate groups of chinchillas, (-)pentazocine was given alone or administered in combination with the standard opioid receptor antagonist naloxone administered at two doses. RESULTS: Robust changes in CAP amplitudes after (-)pentazocine occurred in the absence of measurable alterations in CAP response latencies, CM amplitudes, or blood chemistries and were significantly antagonized when naloxone (5 mg/kg) was added to the i.v. infusion. CONCLUSIONS: The observed blockade clearly indicates that the agonist effects of (-)pentazocine are opioid receptor-mediated and suggests a connection between opioid receptors and auditory neural function. Mechanisms of action and the connection between an opioid modulation of auditory function and stress, hyperacusis, and tinnitus are discussed.

Animals↗
PubMed2005

Sacculo-collic pathway dysfunction accompanying auditory neuropathy.

CONCLUSIONS: In a patient with bilateral auditory neuropathy (AN), the vestibular-evoked myogenic potential (VEMP) was probably absent because of a neuropathy involving the inferior vestibular nerve and/or its end organ, the saccule. Our result can therefore be interpreted as a concomitant unilateral sacculo-collic neuropathy. We suggest the use of more precise terms to characterize AN patients with involvement of different parts of the inner ear and its innervations. We encourage detailed vestibular assessment in patients with AN in order to assess the co-existence of any symptomatic or asymptomatic vestibular disorder. Information such as that provided in this report will be valuable for clinicians caring for this group of patients. OBJECTIVE: AN is a disorder characterized by the absence or severe impairment of auditory brainstem responses in the presence of normal cochlear outer hair cell function as revealed by otoacoustic emissions (OAEs) and/or electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology. In most literature reports the auditory profile of patients with AN is discussed. However, the extent of vestibular involvement, especially that involving the saccule, is not known. We performed vestibular tests to assess the status of the saccule in a patient with AN. MATERIAL AND METHODS: One patient with AN was studied. The patient was a right-handed 21-year-old female with chief complaints of hearing loss and speech perception difficulty. RESULTS: The auditory test results were consistent with the diagnosis of AN, i.e. absent auditory brainstem responses, moderate hearing loss, an inappropriately profound speech discrimination score and the presence of OAEs and measurable cochlear microphonics on ECoG. On neurological examination, gait and balance tests were normal. Ice-water caloric testing induced a sensation of dizziness in both ears. Short tone-burst VEMPs showed no response on left-ear stimulation and a biphasic response with normal latency and amplitude on right-ear stimulation.

Adult↗
PubMedDate not supplied

Study of neural excitation in the guinea pig cochlea using low-frequency acoustic modulation.

A low-frequency tone has been shown to modulate the amplitudes of cochlear microphonic (CM) and whole nerve (N1) response to a high-frequency tone pip. Whereas the N1 responses was always reduced and had two maxima per cycle of the low-frequency signal, the CM response changed from a single- to a double-maxima pattern as the modulator intensity was increased.

Acoustic Stimulation↗
PubMed2003

Screening methods: current status.

Two technologies are currently used to screen newborn infants for hearing, auditory brainstem response (ABR), and otoacoustic emissions (OAEs). Each technology is based on detecting the infant's physiologic response to auditory stimulation. ABR is a short-latency auditory evoked response originating from eighth nerve and brainstem auditory pathway structures and detected by scalp surface electrodes. OAEs are auditory signals generated by cochlear outer hair cells in response to acoustic stimulation and detected by a miniature microphone coupled to the infant's ear. Although each technique requires specific sound generation and response recording technologies, advances in computerized stimulus delivery and response detection algorithms allow these tests to be performed by trained technicians or volunteers under the supervision of an audiologist. Results of test performance, and the advantages and disadvantages of each technique are described.

Evoked Potentials, Auditory↗