Guidelines for quantification of noise-induced hearing loss in a medicolegal context.

OBJECTIVES: Guidelines published in 2000 by the authors are widely used by medical and legal professionals in the UK for diagnosis of noise-induced hearing loss in a medicolegal context. However, they cannot be used for quantification of the noise-induced hearing loss, which is required in most cases. This requirement is addressed. DESIGN: A method is developed here to quantify noise-induced hearing loss, thereby overcoming this shortcoming. SETTING: Assessment of noise-induced hearing loss in medicolegal cases. PARTICIPANTS: A consecutive series of 124 cases of noise-induced hearing loss is used for evaluation. MAIN OUTCOME MEASURE: Magnitude of noise-induced hearing loss based on hearing threshold levels averaged over the frequencies 1, 2 and 3 kHz. RESULTS: The rationale of the method, practical application and three worked examples are developed. A simpler short-cut method is developed and shown to be equivalent to the full method in most cases. CONCLUSIONS: The method offers a practical approach to quantification of noise-induced hearing loss.

Asymmetric sensorineural hearing thresholds in the non-noise-exposed UK population: a retrospective analysis.

OBJECTIVES: To estimate the distribution of inter-aural sensorineural hearing threshold level differences in the non-noise-exposed adult population of the UK. SETTING: A two-stage population study carried out in 1979-1986, initially by postal questionnaire, followed up in a proportion of participants by clinical and audiological examination. PARTICIPANTS: Volunteers (n = 48 313) initially selected at random from the electoral registers of four cities, subsequently selected at random from questionnaire respondents stratified by answers to questions about hearing. MAIN OUTCOMES MEASURE: Inter-aural hearing threshold level differences measured audiometrically, as a function of age and gender. RESULTS: Tables of inter-aural threshold level differences provided as a resource with potential medicolegal, clinical and research applications. Based on the average of the frequencies 0.5, 1, 2 and 4 kHz, approximately 1% of the general UK population aged 18-80 years have an asymmetry of 15 dB or more. The prevalence is greater in older than in younger people. CONCLUSIONS: Inter-aural threshold differences greater than attributable to measurement error are not uncommon in the adult population, even after screening for conductive hearing loss and substantial noise exposure. They are typically of unknown origin.

Guidelines on the diagnosis of noise-induced hearing loss for medicolegal purposes.

These guidelines aim to assist in the diagnosis of noise-induced hearing loss (NIHL) in medicolegal settings. The task is to distinguish between possibility and probability, the legal criterion being 'more probable than not'. It is argued that the amount of NIHL needed to qualify for that diagnosis is that which is reliably measurable and identifiable on the audiogram. The three main requirements for the diagnosis of NIHL are defined: R1, high-frequency hearing impairment; R2, potentially hazardous amount of noise exposure; R3, identifiable high-frequency audiometric notch or bulge. Four modifying factors also need consideration: MF1, the clinical picture; MF2, compatibility with age and noise exposure; MF3, Robinson's criteria for other causation; MF4, complications such as asymmetry, mixed disorder and conductive hearing impairment.

Efficiency of tests used to screen for cerebello-pontine angle tumours: a prospective study.

With increasing use of imaging in the investigation of cerebello-pontine angle (CPA) tumours, the role of audio-vestibular and electrophysiological testing has changed. Field performance data on the efficiencies of these tests to screen for CPA tumours are lacking, but must be known to choose an appropriate testing strategy. A prospective observational study of 237 patients attending a neuro-otology clinic for audio-vestibular investigation was carried out. The aim was to provide field performance data on which to base an effective protocol to screen for CPA tumours. All patients presenting at the ENT department and meeting any of the following criteria were referred to the neuro-otology clinic and included in the study: (1) asymmetrical sensorineural hearing loss, (2) unexplained asymmetrical tinnitus with normal bearing thresholds, (3) unilateral bearing difficulties with normal hearing thresholds and (4) other neurological indications. In addition to audio-vestibular and auditory brainstem response (ABR) investigation, every patient underwent computed tomography (CT), with magnetic resonance imaging (MRI) in cases having marginal results on CT, to exclude or confirm the presence of a tumour. Pass or fail on each test was based on a priori criteria from other studies. Eighteen patients were found to have CPA tumours. ABR testing was the only effective procedure for screening, but had some limitations. A contingent protocol using ABR in all cases except those with asymmetrical tinnitus and normal bearing thresholds, those with severe hearing loss, and those with neurological signs, was retrospectively defined: the exceptions would go straight to CT. This protocol would have missed two of the 18 tumour patients. CT scanning alone would have missed one small intra-canalicular tumour, which was picked up on MRI triggered by abnormal ABR. Based on the results from the present study we conclude there is no effective screening protocol for detecting CPA tumours, as MRI scanning with gadolinium enhancement will identify virtually all tumours. Where MRI is available but waiting lists are long, the described strategy using ABR to select priority referrals for MRI scanning is recommended.

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. about two-thirds of consultants prescribe tinnitus maskers. A total of 66 tinnitus clinics have been identified. The data are interpreted as illustrative of the steady improvements in the last 10-15 years in tinnitus management services.

Intra-tympanic injections in the treatment of tinnitus.

Prolonged reduction or abolition of tinnitus has been reported in about two-thirds of patients treated with a single or weekly-repeated injection through the tympanic membrane of either dexamethasone or lignocaine. In a small-scale trial of these treatments, dexamethasone gave 6 patients little benefit but few side-effects. Lignocaine gave 5 patients no lasting benefit but violent vertigo for several hours. A. Axelsson (personal communication) had similar experience with 6 patients treated with intra-tympanic lignocaine. It is concluded that this form of treatment does not seem sufficiently effective to offset its low acceptability.

Indications for aspirin as a palliative for tinnitus caused by SOAEs: a case study.

This paper explores the effect of aspirin on the tinnitus of one patient for whom two contralateral spontaneous otoacoustic emissions (SOAEs) caused binaural tinnitus. The relation between the SOAEs and tinnitus was explored during a preliminary testing session, after which the SOAEs were measured for 7 days. During days 1, 2, 5, 6 and 7 of the trial, a placebo (two 50-mg tablets of ascorbic acid) was administered four times per day. During days 3 and 4, a drug (two 300-mg tablets of aspirin) was administered four times per day. During day 2, the right ear's SOAE was low level and labile, sometimes disappearing into the noise floor. The effect of aspirin on an emission which is not consistently observed, cannot be assessed so this report focuses primarily on the left ear. During days 1 and 2, the SOAE in the left ear was present and the tinnitus was audible. By day 3 (after 2.4 g of aspirin), the SOAE in the left ear had been abolished, and the tinnitus was not audible. On the fifth day (24 hours after the last aspirin), both the SOAE and the tinnitus in the left ear had returned. There were no reported side-effects of the aspirin. Thus, aspirin seemed to provide an acceptable palliative for this patient's SOAE-caused tinnitus.

Occupational noise induced vestibular malfunction?

This paper comprises a review of the evidence for the possibility that exposure to noise may damage the vestibular receptors in the internal ear as well as those in the cochlea. The review covers lay and medical publications, observations on patients, experimental studies, and compensation claims. It concludes that the verdict must be "not proven"--that is, although such damage is possible, the evidence is not strong enough to regard it as probable.

The limited accuracy of bone-conduction audiometry: its significance in medicolegal assessments.

Accurate bone-conduction testing with masking is always difficult, but for clinical purposes limited accuracy suffices. However, when assessing claimants for compensation, extreme care is needed since even small apparent air-bone gaps are sometimes translated into financial abatement. This paper sets out the stringent test conditions required to achieve adequate precision. It also indicates the inaccuracies inherent in such tests, and recommends procedures for interpreting the significance of bone-conduction thresholds.

Trial of flecainide acetate in the management of tinnitus.

A two-phase trial of flecainide acetate in the management of tinnitus has been carried out in 22 patients with severe long-term tinnitus resistant to other treatments. Although 5 (23%) patients reported some limited benefit the results are not conclusive but suggest that, for such patients, flecainide deserves a place as a drug worth considering as a last resort, with the prospect of it occasionally giving a worthwhile degree of relief.

Comparative study of four noise spectra as potential tinnitus maskers.

Ten experienced tinnitus-masker uses compared four widely different noise bands as potential maskers in a laboratory environment. No reliable individual preferences could be found, and most of the noises were acceptable to most of the subjects. A wide-band noise was marginally most frequently preferred. In this sample, there was no indication that individual tailoring of the frequency spectra of tinnitus maskers is required to achieve acceptable masking. Subjects also underwent tests of hearing, tinnitus matching and tinnitus masking. Most subjects chose noise levels for therapeutic masking that only partially masked their tinnitus. This suggests prescription or trial of tinnitus maskers even for patients who have high minimal masking levels.

Self-reported disability and handicap in the population in relation to pure-tone threshold, age, sex and type of hearing loss.

A self-administered questionnaire concerning auditory disability and handicap was completed by 1691 subjects who were part of a two-stage random sample of the UK adult population. A principal components analysis of questionnaire replies identified four components. They were interpreted as (a) disability for everyday speech, (b) disability for speech-in-quiet, (c) localisation, and (d) hearing handicap. Components (a) and (d) were the strongest, accounting for 68% of the variance. Subjects also performed pure-tone audiometry amongst other tests. Audiometric information was well described by a two-parameter model characterised by low-to-mid-frequency loss and high-frequency slope. All four components increased progressively with increasing low-to-mid-frequency loss, independent of high-frequency slope. They were best correlated with a binaural average over 0.5, 1 and 2 kHz weighted 4:1 in favour of the better ear, out of several audiometric descriptors examined. Sex and socio-economic group did not generally affect disability or handicap, but people of similar hearing impairment reported less disability and handicap as age increased. This is interpreted as over-compensation for the effects of age in self-report. There were three unexpected findings which may entail some changes in current thinking on the relationship between auditory impairment and self-perceived disability/handicap. Hearing losses incorporating a conductive component in the better ear were more disabling and handicapping than sensorineural losses of equal magnitude. Localisation ability and, to a lesser extent, general hearing handicap were more highly correlated with measures of impairment in the worse ear than in the better ear. There was little evidence for the concept of a 'low fence' in the relationship between impairment and either disability or handicap.

A clinical study of tinnitus maskers.

This report describes a three-centre study of the effectiveness of tinnitus maskers, combination instruments (masker plus hearing aid), and hearing aids in the management of tinnitus. Some 472 patients entered the study with 382 reaching the first evaluation session after a minimum period of 6 months from fitting, and 206 reaching the second evaluation not less than 6 months after the first. The study included two control groups, by which to assess the comparative benefit to be derived solely from the investigation and counselling of such patients. The principal results were as follows: thorough investigation and careful counselling do much to help the patient; much further benefit is given by tinnitus masking instruments of various kinds; maskers are more often effective than hearing aids, although the latter are frequently the most appropriate first treatment of those patients who have substantial (but not yet treated or insufficiently treated) hearing difficulties as well; there is no evidence of masking having any harmful effect on hearing. None of the audiometric or tinnitus tests currently employed can be regarded as predictive, either of tinnitus severity, or of the eventual outcome of masking therapy, however certain measurements may help as a guide to patient management.

Measurement and management of tinnitus. Part I. Measurement.

This paper comprises mainly a description of the clinical practice and experience of the Tinnitus Clinic at the General Hospital, Nottingham, which has evolved as a result of and during the course of a 3-year DHSS-sponsored study of the efficacy of tinnitus maskers. The paper is supported by some experimental data from laboratory, epidemiological and clinical studies, and by information on the number of patients who can be seen, the staff required and the methods used in the clinic.

The results of cortical electric response audiometry in medico-legal investigations.

Cortical ERA was conducted in a consecutive series of 118 medicolegal cases (467 threshold determination in 209 ears). In organic cases, the distribution of subjective (manual pure tone audiometry)/objective (CERA) discrepancies was normal and centred on 0 dB, with only 3.2% of the discrepancies exceeding + 15 dB. Averaged over 3 or more test frequencies in one ear, only 4.4% of the discrepancies exceeded + 7.5 dB, as compared to 95.1% exceeding + 7.5 dB in those suspected of having a non-organic overlay. The pattern of non-organic overlay superimposed on noise-induced hearing loss is expected and demonstrated to produce a flattening of the dip in the audiogram. It is argued that such flattening is very rarely the end product of noise exposure.