The behaviour of wave V latency in cochlear hearing loss

Absence of otoacoustic emissions in insulin-dependent diabetic patients: is there evidence for diabetic cochleopathy?

In order to evaluate cochlear function in Type 1 diabetes mellitus, this study analyses otoacoustic emissions (OAEs) on normal hearing subjects with diabetes and on controls. Patients with Type 1 diabetes (n=60), with a mean age of 31+/-6.23 years, mean disease duration of 17.5+/-8.9 years, and mean HbA1c of 8.1+/-1.8%, of whom 43% had signs of retinopathy and 28% had clinical signs of neuropathy, were studied. All patients underwent an OAE analysis and brainstem-evoked potentials. Fifty-eight normal volunteers were used as controls for the OAE analysis. Seventeen patients (28.3%) had no OAEs in at least one ear and 10% in both ears. The mean intensity of the response was lower in diabetic subjects [7.1+/-4.4 vs. 10.9+/-9.3 dB SPL (sound pressure level)] than in controls. The cochlear impairment was over 5 dB for the 1-kHz frequency, which is the critical level for speech understanding. These findings suggest that cochleopathy can be detected in a relatively high proportion of subjects with Type 1 diabetes in spite of a normal audiometric hearing threshold.

A study of the effects of cochlear loss on the auditory brainstem response (ABR) specificity and false positive rate in retrocochlear assessment

The auditory brainstem response (ABR) test is widely used as a screen for retrocochlear dysfunction in individuals suffering idiopathic auditory and vestibular disturbance. Although its sensitivity for lesions of the lower brainstem is well established, hearing loss is known to have significant effects upon the test's specificity and false positive rate. This study analysed the effects of aspects of cochlear hearing loss including level, slope and general audiogram shape on these properties of the ABR test in a large clinical group. The study comprised 306 patients (153 male, 153 female) referred for ABR screening to exclude retrocochlear dysfunction. Of 566 ears meeting the inclusion criteria, 85 (15 per cent) failed the test. On follow-up eight ears (3 per cent) were confirmed to have some form of retrocochlear abnormality, seven of which were pathological. All had abnormal ABR results. No cases of retrocochlear abnormality were found in the ABR pass group. In those patients diagnosed as free of retrocochlear problems, the importance of the I-V interval as a primary index of function was confirmed. It displayed a high specificity (>90 per cent) which was largely independent of the level or slope of high-frequency hearing loss. In contrast wave V specificity decreased with increasing loss and increasing slope. Its value as a functional index was limited with losses greater than 70 dB HL in whom specificity fell below 70 per cent. The study concluded that, despite reducing interval availability above 60 dB HL, wave V latency cannot be used as an alternative index because it displays weakening specificity over this range of loss. With the problems inherent in applying latency corrections, the author advocates the use of improved procedures for wave I identification in these cases.

The effects of cochlear hearing loss, age and sex on the auditory brainstem response

This study analyzed the effects of auditory impairment, age and sex on the auditory brainstem response (ABR) wave latencies. ABR wave I, wave V and I-V interval measures were extracted from the clinical records of 201 patients with cochlear hearing loss. Females had consistently earlier wave V latencies and shorter I-V intervals than males. No age effects were observed. Degree of impairment had a systematic effect on ABR wave latencies and I-V intervals. Wave I displayed latency extension with increasing levels of high-frequency hearing loss, whilst for wave V increases in latency were dependent upon both degree and slope of the hearing loss. Present results suggest that many of the previously reported sex differences and variable interactions seen for the ABR can be accounted for by differences in the underlying distribution of audiogram shapes within and between study populations. Different audiometric configurations were found to produce consistent differential effects on both wave I and wave V latency and thus influence the I-V interval. This study underlines the need to develop a more detailed model of impairment effects if correction factors are to be employed more effectively in ABR testing for retrocochlear pathology.

Wave V latency shifts with age and sex in normals and patients with cochlear hearing loss: development of a predictive model

In order to study the combined effect of age, sex and cochlear hearing loss on the auditory brainstem response in an adult population, absolute wave V latency measurements were made in 117 ears of 64 patients with cochlear hearing loss and 105 ears of 58 otologically normal control subjects. Among normals, wave V latency was found to increase with age. Latencies in female subjects were significantly shorter than in male subjects. The best predictive model for wave V latency in normals was: wave V latency (ms) = 4.982 + 0.007 x age + 0.091 x sex, where age is measured in years and sex is given a value of 1 for females and 2 for males. In patients with hearing loss, wave V latency increase was determined largely by the degree of hearing loss and the effect of age was moderate. The influence of sex was minimal. Wave V latency in patients with hearing loss was predicted by the formula: wave V latency (ms) = 4.911 + 0.007 x hearing loss + 0.004 x age + 0.081 x sex. These predictive models can be utilized to accurately estimate expected wave V latency in patients with cochlear hearing loss.

Correcting for factors affecting ABR wave V latency

The latency of auditory brainstem response (ABR) wave V has been shown to be affected by several subject and technical factors. Previous studies have often concluded with a recommendation to account or correct for one or more of these factors when latency is used as a means of detecting retrocochlear dysfunction. This study investigated the effect of subject age, sex, hearing loss and stimulus intensity on ABR wave V latency in a group of 189 clinical subjects in whom retrocochlear disease was effectively excluded. Regression analysis showed that all four factors exerted a significant influence on latency and that hearing loss and intensity were most effectively represented when combined to form a sensation level variable, together with a measure of audiogram slope.

Observations on the ABR I-V interval in a clinical sample of elderly patients

ABR I-V interval in elderly patients, analysed by multiple regression analysis, was found to be dependent on hearing threshold slope and sex, while the contribution of age and hearing loss was not significant. Since these results partly disagree with other reports which demonstrate that I-V interval is significantly related to age and hearing threshold, caution is suggested in inferring general conclusions on age effects, if data are drawn from clinical samples.