Silvano Prosser

Effects of different noises on speech discrimination by the elderly

Elderly people often complain of difficulty in speech discrimination, especially in noise environments. The effects of 4 competing noises on sentence intelligibility were evaluated: speech noise, cocktail party noise, traffic noise and continuous discourse. A comparison was made between young and old normally hearing subjects and young and old hearing-impaired subjects with similar audiograms. The old people with normal hearing had slightly reduced discrimination compared to the young during competing speech noise and cocktail noise. Discrimination in the hearing-impaired elderly was also significantly worse than in the young people with normals hearing, during competing cocktail party noise, traffic noise and continuous discourse. The young hearing-impaired had results between young normal-hearing subjects and old hearing-impaired, except for continuous discourse. Thus the effects of age on speech discrimination in noise are subtle, becoming more pronounced in the presence of hearing loss. Age-related changes in primary speech discrimination were particularly evident during competing continuous discourse.

Habituation and rate effect in the auditory cortical potentials evoked by trains of stimuli.

SummaryThe effects of the stimulus repetition rate over the habituated auditory cortical evoked responses were studied. The stimulation pattern consisted of trains of pure tone bursts with interstimulus interval (ISI) of 1 s, and intertrain interval (ITI) of 5 s, delivered with constant time and intensity parameters during 93 min. The analysis of the responses was based upon across averaging of the trains, each single response being evaluated in the latency and amplitude parameters. Two time-dependent factors affected the responses in a distinct way: the habituation throughout the whole stimulation and the rate effect within the train. The linear regressions of the time/amplitude functions of the responses were calculated in relation to the duration of ISI and ITI. By introducing a correction factor depending on the repetition rate it was possible to evaluate the relationships between habituation and repetition rate. Changes in the repetition rate do not have any effect on the habituation process. The two phenomena are completely distinct, and they probably have neurophysiologic substrates corresponding to different levels in the central nervous system (CNS).

Hearing loss in sports hunters exposed to occupational noise

The hearing level of 133 railway workers who also hunted for sport was evaluated and compared with that of 82 non-hunting colleagues. Both groups were affected by hearing loss, mostly involving the high-frequency range. Hunters were found to differ from non-hunters by having significantly worse hearing threshold in the ear contralateral to the shoulder supporting the firearm. The interaural threshold difference at 4 kHz was related to the number of rounds fired and exposure duration, thus providing an estimate of the adverse effect of gunfire noise to which the hunters had been exposed.

The Auditory Brainstem Response to Binaural Delayed Stimuli in Man

The brainstem responses (BER) evoked by binaural clicks (0.1 ms) with interaural time differences (delta t) from 0 to 3.5 ms were studied in 6 normal subjects. The responses analysis was carried out via computer in two different ways: (a) Comparison between binaural BER and templates obtained with the addition of two monaural BERs. (b) Extraction from the binaural BER of the second delayed pattern. The results suggest that an algebraic addition of the responses from the two stimulated sides is the main mechanism of the binaural BER generation. In comparison with the templates, the binaural response shows some differences which are evident at delta t = 0--1.5 ms and are limited in the region of VI and VII waves. Such differences are caused essentially to an amplitude decrease of the second pattern--that is response to the delayed stimulus--mainly at delta t 1.5 ms. However these results do not allow us to say if the phenomenon recorded at the surface is due to central adaptation or to specific mechanism of binaural interaction.

Does General Anaesthesia Affect the Child's Auditory Middle Latency Response (MLR)?

Auditory MLR and ABR were recorded simultaneously in 9 children under general anaesthesia, after electrocochleography had demonstrated a normal hearing threshold. In contrast to the ABR components which in all cases appeared to be clearly recognizable, and with latencies within the normal range, MLR revealed gross abnormalities represented by instability of the components and abnormal latency of the detectable peaks. Since such variations in the MLR pattern may be thought of as a direct consequence of general anaesthesia, it seems likely that these potentials reflect a neural activity which, in children, is affected by CNS drugs.

Evaluation of the Monaurally Evoked Brainstem Response in the Diagnosis of Sensorineural Hearing Loss

The auditory brainstem responses (ABRs) obtained in 47 subjects with asymmetric hearing loss (12 with surgically confirmed cerebello-pontine angle tumours, 35 without otoneurologic and/or neuroradiologic evidence of tumour) were evaluated by means of an index named delta V. The calculation of this index was based upon the patients wave V absolute latency obtained at a fixed intensity of 90 dB HL and the value of latency predictable by means of the normative data. The index clearly separates retrocochlear from cochlear sites of lesion. Moreover delta V values obtained in defined cochlear lesions show a linear relation with the patients pure tone hearing loss at 2 and 4 kHz; this behaviour is probably due to a reduction of the auditory dynamic range in the recruiting ears. delta V appears to have clinical usefulness because of two main points: first it is based upon an evaluation of the monaurally evoked ABR; second, it improves the diagnostic specificity of the responses. The rate of false positive results can be further reduced by combining delta V and IT5 values.

Audiometric Patterns of Genetic Non-syndromal Sensorineural Hearing Loss

Sixty-five families with non-syndromal sensorineural hearing loss (NS-SNHL) of genetic aetiology were subtyped according to Gorlin et al. Individual audiogram shapes were also classified in order to detect inter- and intra-familial variations. In 48 families with an Autosomal Dominant (AD) inherited form, 26 exhibited the features of (high-frequency) progressive NS-SNHL, 12 those of mid-frequency NS-SNHL, 5 were affected by congenital low-frequency NS-SNHL; 1 kindred showed a progressive low-frequency pattern and another 1 a unilateral NS-SNHL; only 3 kindreds were affected by severe congenital NS-SNHL. Autosomal Recessive (AR) inherited forms were composed of 9 kindreds with severe congenital NS-SNHL, and 7 with moderate congenital NS-SNHL. One X-linked form was identified. AD- and AR-inherited NS-SNHL differed significantly both in severity of hearing impairment and in audiogram shapes. With few exceptions, in each family classified according to Gorlin, most of the affected subjects shared the same audiogram profile. Intrinsic progression of the disease versus ageing was studied in the larger subtype of individuals with the high-frequency loss. Gorlins classification still remains the best system to classify NS-SNHL, and can provide a broad base to separate a very heterogeneous group of disorders. Results obtained in gene mapping in single large human families or in homologous gene search could be tested in our families. For some of them, namely those with high frequency progressive and low-frequency NS-SNHL, testing should already be feasible.

A new oral otoprotective agent. Part 1: Electrophysiology data from protection against noise-induced hearing loss

Summary Background Data from animal studies show that antioxidants can compensate against noise-induced stress and sensory hair cell death. The aim of this study was to evaluate the otoprotection efficacy of various versions of orally administered Acuval 400® against noise damage in a rat animal model. Material/Methods Fifty-five Sprague Dawley rats were divided into 4 groups: A) noise-exposed animals; B) animals exposed to noise and treated with the Acuval; C) animals exposed to noise and treated with a combination of Coenzyme Q10 and Acuval; D) animals treated only with Acuval and Coenzyme Q10 and with no exposure to noise. All solutions were administered orally 5 times: 24 and 2 hrs prior to noise exposure, and then daily for 3 days. The auditory function was assessed by measuring auditory brainstem responses (ABR) in the range from 2 to 32 kHz at times =1, 7, 14 and 21 days after noise exposure. Results At low frequencies (click and 4 kHz) animals from both A and B groups showed significant threshold shifts in the majority of the tested frequencies and tested times. For the same frequencies, animals from group C presented threshold levels similar to those from group D. At frequencies ≥8 kHz the protective performance of the 2 Acuval groups is more clearly distinguished from the noise group A. At 32 kHz the 2 Acuval groups perform equally well in terms of otoprotection. Animals in Group D did not show any significant differences in the hearing threshold during the experiment. Conclusions The data of this study suggest that a solution containing Coenzyme Q10 and Acuval 400®, administered orally, protects from noise-induced hearing loss.

Electrocochleography and brainstem potentials in the diagnosis of the deaf child.

The deaf child must receive sound amplification before he reaches the age of two years. At this age the hearing threshold is best measured objectively by electrocochleography (ECochG) and auditory brainstem response (ABR) audiometry. When used correctly, both methods allow an exact threshold estimation which is informative enough for adequate hearing aid prescription. Both methods have advantages and disadvantages when used in children. The advantages of ECochG are: (a) a more exact threshold estimation and (b) strictly monaural evaluation. The advantages of ABR are: (a) ease of performance; it is not invasive and does not require general anaesthesia and (b) allows for exploration of higher levels in the auditory pathway up to the midbrain. We believe that ECochG and ABR are compatible and complementary in the diagnosis of childhood deafness. ABR could be used in first instance, while ECochG could be reserved for doubtful cases and for those who cannot be adequately sedated. Extra-audiological factors such as the availability of anaesthetists and varying hospital facilities, play a further role in determining the choice of electric response technique.

Considerations on the physiopathological mechanism of inner ear damage induced by intravenous cocaine abuse: Cues from a case report

OBJECTIVE Aim of the following paper is to discuss about the possible etiopathogenetic mechanisms of inner ear damage induced by cocaine abuse. Unfortunately the data concerning this topic are very limited; the authors are then presenting a literature review, also discussing the clinical presentation and the possible therapeutical approach of a clinical case of bilateral sudden sensorineural hearing loss following i.v. injection of cocaine. PATIENTS Case report. INTERVENTION A strictly audiological evaluation has been performed, in order to identify the cochlear lesion site(s) and to provide the best medical treatment. CONCLUSIONS To our knowledge, this is the first report of acute cocaine intoxication with sudden bilateral hearing loss. Further studies are required in order to understand the effects of these substances on the inner ear cells and metabolism.