The feasibility of evoked otoacoustic emissions as an in-patient hearing check after meningitis.

The desirability of finding children with hearing impairment after bacterial meningitis as soon as possible prompted us to examine the feasibility of using evoked otoacoustic emissions (EOAE) as an in-patient check of hearing status in children recovering from bacterial meningitis. Sixty-six episodes of bacterial meningitis were studied. Traces could be recorded for only 54.

Light (Blt), a mutation that causes melanocyte death, affects stria vascularis function in the mouse inner ear.

The Light mutation (Blt) is a dominant allele of the b-locus on mouse chromosome 4 which causes progressive dilution of coat colour. Melanocytes within the hair follicles of mutant mice develop normally but later degenerate, due to the accumulation of a toxic product, so that the hair becomes lighter with age. Previous studies on W-locus spotting mutants, from which melanocytes are absent, have shown that melanocytes in the stria vascularis of the inner ear are essential for the development and/or maintenance of the endocochlear potential (EP) which is normally around 100 mV.

The response of guinea pig auditory-nerve fibers with high spontaneous discharge rates to increments in intensity.

We have re-examined the response of auditory-nerve fibres with high spontaneous discharge rates to increments in intensity as a function of the delay of the increment. In agreement with previous studies, the response measured over a relatively long time window (10 ms), emphasising the properties of short-term adaptation, did not decrease with the delay of the increment. However, the response to an increment in intensity, measured over a short time window (0.

High rate otoacoustic emissions.

One of the practical problems of testing young children using evoked otoacoustic emissions (EOAEs) is that there is a need for the child to be quiet for a period of a minute or so. To achieve this can mean test periods of 10 min or longer. A new application of maximum length sequences (MLSs) to EOAEs is described that enables the test to be performed in a few seconds or less.

Epidemiology of bacterial meningitis.

This 10 year retrospective study of all causes of bacterial meningitis for children resident in Nottingham District Health Authority area reports an annual incidence rate per 100,000 children aged 0-16 years of 16.0 (95% confidence interval 14.0 to 18.

Auditory brainstem responses recorded at fast stimulation rates using maximum length sequences.

There are now commercially available systems which can provide maximum length sequence averaging techniques. This study examines the effects on auditory brainstem response amplitude and latency of using such a system and stimulating at rates from 9 to 1000 clicks/s. As expected there is considerable adaptation of the response such that at 1000 clicks/s wave V amplitude is only approximately 8% of its low stimulation rate value.

Prevalence of tympanogram asymmetries and fluctuations in otitis media with effusion: implications for binaural hearing.

It has been suggested that asymmetric or fluctuating hearing in otitis media with effusion (OME) could lead to abnormal binaural hearing. In a cohort of children with tympanogram data obtained at 3-monthly intervals from 2 to 4 years, 6.4% had asymmetric or unilateral B tympanograms on more than half the test occasions, or had 5 or more fluctuations between symmetric and asymmetric tympanograms.

Comodulation masking release as a function of type of signal, gated or continuous masking, monaural or dichotic presentation of flanking bands, and center frequency.

Thresholds were measured for detecting a signal centered in a narrow-band noise (NBN) masker (on-frequency band, OFB), for the OFB alone, and with two flanking bands (FBs) added to the OFB, one centered above and one below the OFB. The FBs were either correlated with the OFB or were independent and were presented either to the same ear as the signal plus OFB (monaural condition) or to the opposite ear (dichotic condition). The OFB and FBs were either gated with the signal, or were presented continuously.

Click-evoked otoacoustic emissions: new techniques and applications.

There are practical, clinical circumstances in which a decrease in test time for evoked otoacoustic emissions would be of economic or practical value. In addition, there are circumstances in which it is desirable to obtain more diagnostic information from the evoked emission. This preliminary report concerns predominantly one of these aspects but considers both of them.

Reliable identification of click-evoked otoacoustic emissions using signal-processing techniques.

As neonatal hearing screening programmes based on click-evolved otoacoustic emissions (CEOAEs) become more common, there is a need for automatic scoring methods to classify responses systematically. Such methods must guard rigorously against errors that would pass a baby who would otherwise fail and be referred for further diagnostic testing. Preliminary analysis of a wide range of CEOAE waveform characteristics from adult and neonatal ears suggested that the most reliable measure on which to base an automatic method was the cross-correlation coefficient between replicate non-linear components.

Hearing impairment in children after bacterial meningitis: incidence and resource implications.

A retrospective review over ten years of childhood cases of bacterial meningitis treated in two hospitals in Nottingham revealed 301 cases: 88.4% of these children survived. The audiological and clinical hospital records of the survivors were examined to see if the children had been assessed for hearing impairment following the illness.

Responses to speech signals in the normal and pathological peripheral auditory system.

The responses to single (/a/ and /i/) and double vowel (/a,i/) stimuli of normal guinea pig cochlear nerve fibres are compared with those from animals with a cochlear hearing loss. When the threshold losses are sufficient to exclude the higher harmonics of the /i/, the temporal representation of the second and higher formants is lost. Smaller threshold elevations allow a representation of the second formant when the vowel /i/ is presented alone.

Characteristics of stria vascularis melanocytes of viable dominant spotting (Wv/Wv) mouse mutants.

The Wv mutation lies in the kinase domain of the proto-oncogene c-kit which is expressed in a variety of cells including neural crest derived melanoblasts. The mutation results in the abnormal migration, proliferation, survival and/or differentiation of melanoblasts. Viable Dominant Spotting (Wv/Wv) mouse mutants have a white coat due to the absence of melanocytes.

The effect of posture on three objective audiological measures.

This study examines the effect of posture on click evoked otoacoustic emissions, tympanic membrane displacement, and travelling wave velocity obtained using the auditory brainstem response. Statistically significant changes with posture were observed for each technique. The changes in evoked emission and tympanic membrane displacement measurements were comparable with those reported by previous experiments.

Apportionment of noise-induced hearing disability and its prognosis in a medicolegal context: a modelling study.

Apportionment of liability for noise-induced hearing loss is required in medicolegal work when two or more separate instances of noise exposure have occurred. In general there are insufficient audiometric records to determine how much hearing loss was caused by each noise exposure, and hence there is insufficient information on which to base apportionment of liability. Apportionment must then be based on a theoretical understanding of the way in which hearing loss is related to patterns of noise exposure and how the increased hearing threshold levels lead to greater disability.

Quantification of hearing disability for medicolegal purposes based on self-rating.

Current practice for medicolegal assessment of individuals entails the use of an impairment measure obtained from average hearing threshold levels as a surrogate for hearing disability, and conversion of the surrogate to disability via a formula. Several different formulae are in use, but none is based explicitly on experimental data. To address this lack of empirical foundation in the assessment process, numerical self-ratings of hearing ability by 2058 subjects with a wide range of hearing threshold levels who had taken part in the National Study of Hearing in the UK were analysed to examine their relation to average hearing threshold level.

The time course and magnitude of perceptual acclimatization to frequency responses: evidence from monaural fitting of hearing aids.

At high presentation levels, normally aided ears yield better performance for speech identification than normally unaided ears, while at low presentation levels the converse is true [S. Gatehouse, J. Acoust.

Is hearing assessed after bacterial meningitis?

A questionnaire was sent to 686 paediatricians in the UK to discover whether or not they referred children for hearing assessment after bacterial meningitis and if not, why not; 90% replied. Of these, 10% did not refer all children. The reasons given were based on misunderstandings of the aetiology and not on a lack of provision.

Normal hearing in Splotch (Sp/+), the mouse homologue of Waardenburg syndrome type 1.

Splotch is considered a model of Waardenburg syndrome type I (WSI) because the abnormalities are caused by mutations in homologous genes, Pax-3 in mice and PAX3 (HuP2) in humans. We examined inner ear structure and function in Splotch mutants (Sp/+) and found no sign of auditory defects, in contrast to the deafness in many WSI individuals. The difference in expression of the genes in the two species may be due to different parts of the gene being mutated, or may result from variations in modifying influences as yet undefined.

The development and interpretation of the summating potential response.

The development of cochlear responses in the mouse was investigated, recording from the round window. Positive summating potentials (SP) could be detected as early as 7 days after birth in some individuals, the first signs of negative SP occurred in mice aged 10 days, and compound action potentials were first detected at 11 days of age. These early responses were obtained with relatively low frequency stimuli (usually 6 kHz).

The prevalence of middle ear disease in the adult British population.

The UK National Study of Hearing set out to ascertain the prevalence of hearing impairments of various magnitudes, the prevalence of ear disease and the associated risk factors, and to estimate the percentage of individuals requiring some form of management. A stratified sample of 2708 British adults, aged 18-80 years, was chosen from a sample of 48,313 adults, randomly selected from the electoral roll, for a full otological and audiological assessment. This paper deals primarily with the middle ear results.

A survey of tinnitus management in National Health Service hospitals.

This paper reports the results of a postal questionnaire survey to ascertain the current status of NHS hospital services for patients with tinnitus. Statistics are given on the various managements used, e.g.

Lack of association between otoacoustic emissions and hearing difficulty in subjects with normal hearing thresholds.

Evoked otoacoustic emissions (EOAE) are a sensitive indicator of subtle cochlear damage and hence might explain why some people complain of excessive difficulty understanding speech in a background of noise, despite having normal hearing thresholds. This phenomenon has been termed "Obscure Auditory Dysfunction" (OAD). Recorded EOAE waveforms from a group of 50 OAD patients were compared with those from a group of 50 matched controls.

The clinical assessment of "Obscure Auditory Dysfunction" (OAD) 2. Case control analysis of determining factors.

Obscure Auditory Dysfunction (OAD) is defined as a clinical referral for self-reported auditory disability with no audiometric abnormality by stringent criteria. In stage 2 of a case control study of OAD, we have confirmed the general finding of stage 1 that OAD is multifactorial; compared with controls, patients as a group have a genuine performance deficit for understanding speech in noise, accompanied by personality-related factors. Paired logistic regression analysis optimally differentiated the 50 patients from their 50 matched controls on the basis of variables from three different domains: masked thresholds (psychoacoustic domain), dichotic listening ability (central/cognitive domain), and underestimation of own hearing ability (personality domain).