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Biomedical subjects

H A Beagley

Publications and source records attributed to H A Beagley.

At least 19 recordsLinked to original sources
PubMed1985

Acoustic brainstem responses for clinical use: a comparison of pure tone stimuli with wide band clicks.

The acoustic brainstem response (ABR) in clinical use is generally elicited by a wide band click stimulus. This gives a well-synchronized response detectable at low sound intensities, but requires tedious biological recalibration which could be largely eliminated by the use of pure tone pip stimuli. We have therefore assessed ABRs in response to pure tone pips at 2 KHz and 4 KHz. This has shown that these tone pips elicit a much poorer response than clicks, having thresholds which are both significantly higher, and more widely distributed. We therefore conclude that wide band clicks remain the most satisfactory stimulus for clinical use.

Acoustic Stimulation↗
PubMed1985

Acoustic brainstem responses for clinical use: the effect of attention.

The acoustic brainstem response (ABR) is generally thought to be unaffected by variation in attention; however, recent papers suggest that during visual distraction of the subject wave Nv may be delayed. We have examined the ABRs of 22 normal subjects in states of auditory attention and visual distraction, using routine clinical testing procedures. We have shown that under these conditions altered attention states have no demonstrable effect on the latency of wave Nv.

Adult↗
PubMed1984

A nine-year review of 841 children tested by transtympanic electrocochleography.

The case notes of 841 subjects who had had ECochG carried out between January 1972 and December 1980, were examined and the results compared with PTA results in 263 cases in which these were available. ECochG was found to be a good predictor of peripheral hearing as long as its limitations were recognized, and some of these are discussed. BSER, which has similar limitations, was also found to be a good predictor of peripheral hearing, although slightly less sensitive, and sometimes gave additional information on the hearing loss and the clinical state of the patient.

Action Potentials↗
PubMed1979

Temporary threshold shift, loudness, and auditory evoked potentials.

TTS2 of 20dB was produced in a group of subjects using a 1000 Hz pure tone. All TTS and related measurements were made at 1500 Hz. The recovery of TTS, and of TLS or 'temporary loudness shift' (measured against a reference tone at 20db, 40dB and 60dB SL in the opposite ear), as well as N1-P2 amplitude of the Vertex potential, were plotted. There was an orderly recovery of both TLS and TTS although the rate of recovery of the latter was noticeably more rapid. Recovery of N1-P2 amplitude was much less orderly, although it did recover in much the same way. When the amplitudes were measured at 40dB SL the recovery was more orderly and followed the course of TTS more closely. It was concluded that any relation between N1-P2 amplitude and growth of loudness was indirect.

Acoustic Stimulation↗
PubMed1978

Differences in brainstem response latency with age and sex.

Brainstem evoked potentials in response to clicks at 60dB, 70dB and 80dB were recorded from a group of 70 normally hearing subjects. There were 10 subjects (5 male, 5 female) for each of the decades from the second to the eighth. The youngest subject was 14 years, the oldest 79 years. The possibility of there being increased latencies as a function of age was examined. The results indicated that there was, for practical purposes, no such increase. On the other hand there was very strong evidence that in females latenceis are shorter than in males. In addition, amplitudes were reduced in the case of older subjects. Condifidence limits for latency were calculated. These may be helpful in deciding whether or not a particular latency is outside the normal range.

Acoustic Stimulation↗
PubMed1977

Electrocochleographic changes in acoustic neuroma: some experimental findings.

Reversible experimental lesions were produced in the central end of the cochlear nerve at the IAM of guinea pigs by various procedures, including the instillation of KCl (0.1 or 0.01 M). As a result the usual diphasic AP waveforms seen in guinea pigs (when click stimuli are used) were transformed into monophasic, widened negative waves. This change, attributed to a neural block, was reversible, e.g. when the instilled KCl was dispersed by irrigation with normal saline. It is suggested that the widened monophasic negative AP's observed at ECochG in cases of acoustic neuroma or similar lesions, are produced in this way.

Action Potentials↗
PubMed1976

Transtympanic electrocochleography in the diagnosis of retrocochlear tumours.

Transtympanic electrocochleography has been used as a diagnostic procedure in over 250 adult patients with sensorineural deafness. No complications have been encountered. Among these patients vestibulocochlear Schwannoma (acoustic neuroma) has been confirmed in 56 ears while 11 other ears have been found to be affected by other space-occupying lesions. As a result of our observations in these patients, we would like to propose that there are at least three separate criteria to be considered in reaching or strongly suspecting a diagnosis of such pathology. These are broadening of the action potential (loss of P1), observation of a clear microphonic response, and preservation of the action potential even when using stimulus intensities which are not audible in the patients' affected ears. The merits of each of these criteria are discussed and compared with other clinical and operative findings. With the electrocochleographic techniques now employed in searching for acoustic neuromas, false negative results are rare though false positive results are still obtained.

Acoustic Stimulation↗