Management of acute idiopathic sensorineural hearing loss: a survey of UK ENT consultants.

Acute sensorineural hearing loss is a rare event. As yet, there is no standard agreed treatment of this condition because there appears to be little reliable evidence that any one treatment will improve the hearing in these cases. This postal questionnaire was conducted to ascertain the current management of unilateral, acute, idiopathic sensorineural hearing loss by ENT consultants in the UK to see if there is at least a consensus of approach which might lay the foundation for an agreed treatment. Approximately 60% of consultants would admit a patient presenting with these symptoms and only 2% would not prescribe any form of treatment. Of those who do treat the patient, virtually all (99.2%) would prescribe steroids.

Linear and nonlinear temporal interaction components of mid-latency auditory evoked potentials obtained with maximum length sequence stimulation.

A maximum length sequence (MLS) is a quasi-random sequence of clicks and silences that enables simultaneous recording of linear components and nonlinear temporal interaction components (NLTICs). NLTICs are produced when the stimulation rate is fast enough such that several stimuli occur within the memory length of the system. The present study was designed to characterise the NLTICs of auditory mid-latency responses (MLR). Forty normally hearing subjects (19-45-year-old) were tested at MLS rates between 20 and 120 clicks/s. Linear components could be identified at all rates. The NLTICs of the MLS-MLR were identified in only a few subjects. This suggests two possibilities: (1) there may not be strong nonlinear temporal interactions within the MLR generators; (2) the memory length of the MLR is much shorter than expected from the linear component rates. If so, NLTICs should be obtained at higher rates of stimulation.

Auditory brainstem response findings in hypothyroid and hyperthyroid disease.

OBJECTIVE: Retrocochlear sensorineural hearing loss, associated with hypothyroidism, has been reported. This study investigated that claim. METHODS: Audiometric and auditory brainstem response (ABR) measures of patients with hyper- and hypothyroidism. RESULTS: The hyperthyroid group (14 patients) gave no audiometric or ABR results that differed significantly from normal controls. The audiometric findings for the hypothyroid group (21 patients) showed that 36% of this group had a four frequency average threshold greater than 25dB. The statistically significant findings for ABR were a reduction in the amplitude of waves III and V and an abnormal increase in the I-V interval, appearing to confirm a retrocochlear disorder. However, as these patients have a low body temperature, the data were analysed by temperature and the results showed that the ABR abnormalities could be explained by body temperature. CONCLUSIONS: Hyperthyroid patients did not differ significantly from the controls. The four frequency average threshold and ABR results in hypothyroid patients did differ from the controls. However there is no clear evidence that the retrocochlear involvement is a direct result of the hypothyroidism. The abnormalities in the ABR can be explained by the low body temperature seen in these patients. SIGNIFICANCE: This corrects the impression that hypothyroid patients have retrocochlear problems (indicated by ABR); a conclusion confirmed by data from 7 patients after thyroxin treatment when body temperatures were close to normal values and ABR I-V intervals within or near normal limits.

Linear and nonlinear changes in the auditory brainstem response of aging humans.

OBJECTIVE: This experiment was designed to characterize the changes in linear and nonlinear temporal interactions in the aging auditory brainstem of humans using maximum length sequence (MLS) stimulation. METHODS: The MLS technique uses a quasi-random sequence of clicks and silences to determine the linear (linear averaging of single responses) and nonlinear (interactions between pairs or triplets of responses) temporal interactions in the auditory brainstem response (ABR). A group of 30 normal hearing females aged between 11 and 61years were tested. They were divided in three groups: young (<24years); middle (24-41years) and old (>41years). RESULTS: The linear component showed a decrease in wave 5 amplitude with age which could also be related to increased thresholds for higher frequencies. The nonlinear component of the MLS-ABR showed significant differences between middle and old groups for wave 1 and 5 latencies and inter-wave interval (1-5). CONCLUSIONS: The results suggest that the linear and nonlinear components of the MLS-ABR could be more sensitive to changes occurring in the auditory system before any functionally significant changes in hearing status. SIGNIFICANCE: The nonlinear components of the auditory brainstem could be used as an investigative tool to assess early changes in the aging auditory brainstem in young middle-aged women.

An investigation into the relationship between input-output nonlinearities and rate-induced nonlinearities of click-evoked otoacoustic emissions recorded using maximum length sequences.

The maximum length sequence (MLS) technique allows otoacoustic emissions (OAEs) to be recorded using clicks presented at very high presentation rates. It has previously been found that increasing the click presentation rate leads to increasing suppression (termed "rate-suppression") of the MLS evoked OAE (Hine, J.E., Thornton, A.R.D., 1997. Transient evoked otoacoustic emissions recorded using maximum length sequences as a function of stimulus rate and level. Ear Hear. 18, 121-128). It has been suggested that the source of rate-suppression arises from the same nonlinear processes that give rise to the well-known nonlinear growth of OAEs. Based on this assumption, a simple model of rate-suppression (Kapadia, S., Lutman, M.E., 2001. Static input-output nonlinearity as the source of nonlinear effects in maximum length sequence click-evoked OAEs. Br. J. Audiol. 35, 103-112) predicts that both input-output (I/O) nonlinearity and rate-suppression can be unified by characterising the stimulus in terms of its acoustic power which, at high rates, is proportional to the click presentation rate. The objective of this study was to test this simple model by recording MLS OAEs from a group of normally hearing adults over a range of stimulus rates from 40 to 5000 clicks/s, and of stimulus levels from 45 to 70dB peSPL. The results are broadly in agreement with the predictions from the model, though there appears to be some tendency for the model to slightly overestimate the degree of rate-suppression for a given degree of I/O nonlinearity. It is also suggested that the model may break down more significantly in the presence of spontaneous OAEs.

Nonlinear properties of otoacoustic emissions in normal and impaired hearing.

Click-evoked otoacoustic emissions (CEOAEs) exhibit nonlinearities in amplitude and time domains. The first objective of this study was to investigate whether there is any correlation between the temporal and amplitude nonlinearities of CEOAEs in normals. Additionally there is evidence that pathology affects the normal cochlear nonlinearity. The second objective was to investigate whether pathology affects the temporal nonlinear components. Conventional and maximum length sequence (MLS) CEOAEs were recorded in normal subjects and in patients with mild hearing loss. The slope of the input-output (I/O) function of the conventional CEOAE measured the amplitude nonlinearity. Two measures of temporal nonlinearity were the magnitude of the suppression that occurs with increase in stimulus rate and the amplitudes of the second and third order temporal interaction components (Volterra slices). The amplitude nonlinearity is well correlated with both the magnitude of the rate suppression and the amplitudes of the Volterra slices. The 'linear' CEOAE amplitude showed no differences between the normal and patient groups but the differences in the Volterra slices were substantial. This suggests that the first sign of damage to the cochlea is that the system becomes more linear. Hence the Volterra slices may provide a sensitive measure of cochlear damage.

Properties of Volterra slices of otoacoustic emissions in normal-hearing humans obtained using maximum length sequences of clicks.

Nonlinear temporal interaction components of otoacoustic emissions (OAEs) may be investigated by presenting a stream of clicks in maximum length sequences. This yields responses, termed here Volterra slices, which are related to the Volterra kernels of the system. The aim of this study was to obtain normative data on Volterra slices over a range of click rates and stimulus levels. OAEs were recorded in 12 normally hearing adult ears at six rates and four click levels. In addition to the first order kernel, six slices from the Volterra slices of orders 2-5 were extracted from the recordings. It was found that higher order kernel slices could be reliably measured in all 12 ears tested and that they have properties that differ from those of the conventional OAEs. These findings may facilitate the study of cochlear function in both normal and pathological ears.