Search PubMed⌕ Search

Biomedical subjects

S M Mason

Publications and source records attributed to S M Mason.

At least 37 records · Page 2Linked to original sources
PubMed1994

Effect of hearing loss in electrocochleographic investigation of endolymphatic hydrops using tone-pip and click stimuli.

Extratympanic electrocochleography (ECochG) was performed on 37 patients referred to the Evoked Potential Clinic with suspected Ménière's disease. The patients were classified according to their hearing impairment and audiometric configuration. Click and tone-pip stimuli with tone frequencies of 1 and 4 kHz were presented at a rate of 10 per second. Amplitude, latency and general waveform characteristics of the summation potential (SP) and action potential (AP) were analysed for each averaged response with respect to the level and configuration of the hearing loss. The highest incidence of abnormal percentage SP was in patients with average hearing loss in the range of 40-64 dB HL using the click stimulus. In low tone hearing loss, hydrops was identified from an enhanced SP in significantly more patients using the click and 4 kHz tone-pip than the 1 kHz stimulus. Measurement of the width of the 1 kHz tone-pip response waveform was abnormal in some patients even though the click and 4 kHz responses were normal. The optimum stimulus for identification of hydrops from an enhanced SP is dependent on the level and configuration of the hearing loss.

Acoustic Stimulation↗
PubMed1994

Electrocochleography in endolymphatic hydrops using tone-pip and click stimuli.

The use of electrocochleography (ECochG) in the identification of endolymphatic hydrops in Menière's disease, using either trans-tympanic or extra-tympanic recording techniques, has become very popular. The presence of an enhanced summating potential (SP) component is considered to be a diagnostic indicator of hydrops. The response evoked by a click stimulus is widely used in this investigation. The aim of this study was to assess the value of tone-pip stimuli for measurement of the SP component in patients with suspected Menière's disease. Extra-tympanic ECochG was recorded from a surface electrode positioned on the postero-inferior quadrant of the ear canal close to the tympanic annulus. Forty patients referred to the Evoked Potentials Clinic at the Queen's Medical Centre were studied. The combined summating potential and action potential waveform (SP/AP) were recorded using click and tone-pip stimuli. The pips had tone frequencies of 1 and 4 kHz and all stimuli were presented with alternating phase at a repetition rate of 10 per second. The percentage SP (%SP), width and latency characteristics of the SP/AP waveform were calculated for each stimulus condition. There were four patients (10%) with an enhanced tone-pip %SP when the click %SP was within normal limits. Width measurement of the tone-pip waveform at the onset point of the response was abnormal in 13 patients (33%) when a similar measurement of the click-evoked response was normal. There were nine of these patients identified by an abnormal width measurement at the 50% amplitude point of the SP/AP waveform. Both tone-pip frequencies were required in order to identify all these abnormal measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1992

Effects of adaptation on electrocochleography and auditory brain-stem responses in the elderly.

Changes in the amplitude and latency of the evoked potentials in electrocochleography (ECochG) and auditory brainstem responses (ABR) produced by increased stimulus rates (adaptation) were investigated using an extratympanic ECochG technique with simultaneous recording of the ABR in 12 elderly patients, and compared with those of eight normally hearing young adult subjects. Although the absolute latencies of the action potential (AP) and ABR waves were delayed in the elderly, the shift in latency of these components with increased stimulus rate was similar in both groups of subjects. Amplitudes of the AP and wave III component were reduced with increased stimulus rate to a degree which again was similar in both the elderly and young adults. On this basis we suggest that synaptic connections to nerve fibres from surviving hair cells in the elderly are functioning so that disturbance of this part of the acoustic nerve is not a feature of presbycusis.

Acoustic Stimulation↗
PubMed1990

A non-invasive electrophysiological technique for the measurement of 'tuning'.

The frequency selectivity of the auditory system is mainly determined by the activity of the cochlea. A method of measuring this selectivity has been developed by recording the extratympanic compound auditory nerve action potential using non-simultaneous masking. This provides a non-invasive 4-point tuning curve centered at 4 kHz which demonstrates the typical features expected from animal experiments. The non-interactive nature of the test makes it easy to perform and normative data has been collected on 10 subjects.

Adult↗
PubMed1989

Differential diagnostic potential of otoacoustic emissions: a case study.

An 11-year-old boy was identified as having a profound sensorineural hearing loss accompanied by clear click-evoked otoacoustic emissions. Further diagnostic testing by means of electrocochleography and auditory brainstem responses indicated a predominantly retrocochlear disorder with good cochlear function. However, radiological investigation ruled out the presence of any material space-occupying lesion. This case illustrates the contribution that can be made by otoacoustic emission testing to differential diagnosis.

Child↗
PubMed1988

Selective dysacusis--a preliminary report.

The symptom of poor speech discrimination in the presence of background noise is a well-recognized feature of elevated hearing thresholds due to cochlear damage. Similar symptoms occasionally occur in patients with no detectable audiological abnormality. In a study to evaluate the frequency selectivity of such patients consistent abnormalities were found using an electrophysiological technique based on extratympanic electrocochleography. These findings indicated that frequency specific responsiveness of the cochlea may be affected before conventional behavioural tests reveal abnormalities. This syndrome has been described as selective dysacusis.

Adult↗
PubMed1988

Automated system for screening hearing using the auditory brainstem response.

Routine screening of hearing using the auditory brainstem response (ABR) in infants, such as neonates in the special care baby unit, requires a system which is quick, user-friendly and gives a simple outcome. A system which consists of a stimulator/amplifier unit for recording the ABR controlled by a standard Master Series BBC Microcomputer is described which fulfils these requirements. The test procedure is highly automated, and a pass or refer decision for the screen on each ear is given by a machine-scoring algorithm which detects the ABR waveform.

Algorithms↗
PubMed1987

A study of hearing in the elderly using non-invasive electrocochleography and auditory brainstem responses.

The auditory brainstem responses exhibited normal interpeak intervals of waves I-III and I-V in a group of 31 elderly people (mean age 82 years), indicating normal conduction through the brainstem. The amplitudes of the waves I, III and V were significantly reduced and the peaks I, III and V showed a delay in latency, reflecting a predominantly lower level of activity in the elderly cochlea. Extratympanic electrocochleography yielded significantly reduced amplitudes of the N1 component of the action potential, summating potential and cochlear microphonics in the elderly compared to the young controls. A heterogeneity of patterns of input/output functions was observed and interpreted as either an absence of recruitment, as partial or as complete recruitment. The findings are in keeping with pathological evidence of severe damage to outer hair cells and complete atrophy of part of the basal coil.

Adult↗
PubMed1984

Brain-stem, middle latency and late cortical evoked potentials in children with speech and language disorders.

The topography of the brain-stem (ABR), middle latency (MLR) and cortical (ACR) evoked responses was investigated in children with normal speech and language development and those with either a language or motor speech disorder. The aim was to determine whether it is possible to discriminate between the groups of children in terms of the evoked potential characteristics. There were significant inter-group differences, particularly relating to the amplitude of the different responses. The ABR in both the language and motor speech groups exhibited smaller amplitudes for waves I, III and V than the control group, with no change in latency. Two explanations were suggested; firstly abnormal functioning of the peripheral hearing mechanism even though the hearing thresholds were normal which could be a secondary effect due to deprivation of normal speech and language development; and secondly far-field recording effects due to differences in the electrical conductivity of tissue and the distance separating the generator site and recording electrodes. The MLR in the motor speech group was significantly larger at the mastoid and temporal electrode sites than either the control or language groups. This was considered to be an enhanced myogenic response like the other exaggerated brain-stem reflexes seen in congenital suprabulbar paresis. Significantly larger amplitudes of the ACR were also recorded from the motor speech group at the Cz electrode site. This was thought to be due to underactivity of some normal cortical inhibitory system and not a direct result of increased MLR amplitude. The ACR in the language disordered children exhibited an abnormal left temporal hemispheric dominance and a more inverted or 'dissimilar' wave form at the T3 electrode site on the correlation analysis. These findings suggest impaired functioning of the left temporal cortex in our children who have failed to develop language normally. We feel that this has more significance for the language abnormality than the low amplitude ABRs which were observed in both the language and motor speech disordered children.

Brain Mapping↗
PubMed1984

On-line computer scoring of the auditory brainstem response for estimation of hearing threshold.

Auditory brainstem responses (ABRs) to click stimuli have become established as a useful indicator of hearing thresholds in infants and young children. Although the investigation is objective in so far as the patient is concerned, a subjective element remains in the decision by the operator as to whether or not an ABR is present in an averaged waveform. A simple on-line computer detection technique is described which removes some of the reliance placed upon the operator. The technique employs a scanning window for correlation and amplitude analysis of pairs of averaged ABR waveforms. The reliability and accuracy of computer and operator scoring of 25 thresholds in normally hearing adults and 50 thresholds in infants and young children with suspected hearing impairment have been investigated. In the adult group, 96% of computer estimates of the threshold were within +/- 10 dB of the subjective hearing threshold, compared with 92% for operator scoring. There were 92% of computer and operator scores within +/- 10 dB of each other. In the patient group there was equally good agreement between computer and operator scoring with 90% of the thresholds within +/- 10 dB of each other; the incidence of possible false-positive thresholds was also lower with computer scoring. This on-line scoring technique, therefore, offers useful assistance to the operator; requires only limited computing power, and is suitable for use in a routine clinical environment.

Adult↗
PubMed1984

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.

Audiometry↗
PubMed1984

Effects of high-pass filtering on the detection of the auditory brainstem response.

The effects of high-pass filtering on the slow components of the click-evoked auditory brainstem response (ABR) have been assessed in eight normally hearing adults. Eight high-pass Butterworth-type filters (36 dB/octave) were investigated with cut-off frequencies at 10, 20, 30, 40, 50, 60, 80 and 100 Hz (-3 dB points). The low-pass filter was kept constant at 1 kHz. A 20 dB nHL stimulus was presented to the subjects at a rate of 26/s. Two averaged ABR waveforms, each consisting of 2048 individual sweeps, were recorded for each filter setting with a post-stimulus sweep time of 19.2 ms. In the visual interpretation of the recordings the correlation between each waveform, and the amplitude of the response relative to the noise, strongly affects the decision as to whether a response is present. A mathematical analysis of these parameters, using a scanning correlation window technique, showed that a 20 Hz filter is optimum for the best detection of the ABR close to hearing threshold.

Adult↗
PubMed1983

An electrocochleographic study of the effects of lignocaine on patients with tinnitus.

Twenty patients complaining of tinnitus were investigated by extra tympanic electrocochleography (ECochG). Baseline ECochG recordings were carried out, followed by sequential recording after injections first of saline, as a control, and then after lignocaine in the dosage 1.5 mg/kg body weight. Significant improvement in the tinnitus was seen in 13 patients after lignocaine compared with only 3 patients after saline. A statistically significant reduction in the amplitude of the action potential was seen after the lignocaine injection. Our results confirm the views of Melding et al. that the effect of lignocaine is on the neuronal activity of the auditory pathway.

Adult↗