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Biomedical subjects

T Karnahl

Publications and source records attributed to T Karnahl.

At least 19 recordsLinked to original sources
PubMed1979

[Electric response audiometry (brainstem potentials, late auditory potential N1): observations at patients suffering from menière's disease or sudden hearing loss (author's transl)].

At some patients suffering from Menière's disease or sudden hearing loss the late auditory potential N1 and the brainstem potentials were registered. It could be shown, that an exact differential diagnosis between these both illnesses was not possible by means of these acoustically evoked potentials. A statistical analysis of the measured values of the brainstem potential IV ascertained this statement. Furthermore it was not possible by means of these potential to predict an improvement of hearing at patients with sudden hearing loss. Finally the potentials showed an increasing of their latencies which was greater at patients with sudden hearing loss than at patients with Menière's disease.

Audiometry↗
PubMed1978

[Clinical relevance of the early and the late acoustically evoked potentials at Menières disease and at sudden hearing loss (author's transl)].

At some patients suffering from Menières disease or sudden hearing loss the brainstem potentials and the late auditory potential N1 were registered. It could be shown that an exact differential diagnosis between these both illnesses was not possible by means of these acoustically evoked potentials. Furthermore it was not possible by means of these potentials to predict an improvement of hearing at patients with sudden hearing loss. Finally the potentials showed an increasing of their latencies which was greater at patients with sudden hearing loss than at patients with Menières disease.

Brain Stem↗
PubMed1978

[Electric response audiometry (brain stem potentials and late potential N1) in patients with acoustic neurinoma or space-occupying lesion in the region of the brain stem].

In patients with acoustic neuronoma or space-occupying lesion in the region of the brainstem we recorded preoperatively the brainstem potentials as well as the late potential N1. With one exception all patients investigated showed changes in the brainstem potential pattern. When stimulating monaurally there exists a clear side difference, that means the changes in the potential pattern are more distinct on the side of the tumour than on the opposite side and then only if an obstructive hydrocephalus exists. Moreover we could demonstrate in patients with tumours in the region of the brainstem that the brainstem potential IV is no longer suitable for measuring the hearing threshold. On the other hand in these patients an exact determination of the hearing threshold is possible with the late potential N1. Altogether the findings show, that the recording of the brainstem potentials when stimulating monaurally is an important additional diagnostic tool to recognize impairment of the acoustic pathways within the brainstem and probably affords the possibility of perceiving pathological pressure within the brain.

Adult↗
PubMed1977

["On-line artefact rejection" at electric response audiometry (ERA). Use of an active, analog delay line as buffer in combination with a recognition of disturbing signals (author's transl)].

Some brief theoretical considerations about an artefact rejection basing upon the valuation of amplitudes are followed by a report on a new development of an "on-line artefact rejection" which uses an active analog delay line as buffer combined with a recognition of disturbing signals and can easily operate together with simple averagers. The advantages are shown and discussed by means of examples, but also the mistakes which can arise by too great limitations of the signal's level. Technical details are described briefly.

Acoustic Stimulation↗
PubMed1977

[ERA-findings by "cortical hearing disorder" (author's transl)].

Since about the last 2 years the late potential's component N1 (90--110 ms) as well as the early acoustically evoked potentials, appearing in a latency range of 1--8 ms and consisting of the nerve action potential (Pot. I) and the brain-stem potentials (Pot. II-V), were registered at some hearing impaired patients. This procedure enabled us to diagnose a "cortical hearing defect" at five patients: a) three children at an age of 2--3 years; they all have a slight cerebral damage, a hearing impairment and no speech-development; b) a 15 year old girl with a hearing impairment which is on the right side more severe than on the left side, as consequence of an encephalitis; and c) a 50 year old man suffering on both sides from a loss of temporal brain's substance and from a total deafness after an insult of both arteriae meningeae mediae. At all these patients the ERA-findings result in an almost normal behaviour of the bioelectrical transfer of the acoustic stimuli in the region of the brain-stem, whereas the late potential's component N1 showed a pathologic distortion. The ERA-results together with the anammesis make a "cortical hearing disorder" probable at these five patients. The audiograms and the ERA-characteristic lines are shown and discussed.

Adolescent↗
PubMed1977

Does promethazine (Atosil) influence the human's early acoustically evoked potentials in the same way as the late potential N1?

In a former investigation the effect of promethazine (Atosil) on the late acoustically evoked potential component N1 was examined. Now the cochlear and the brain-stem potentials were registered by the earlobe-vertex pick-up with i.m. application of 0.8 mg/kg (body weight) promethazine. There was no influence of promethazine either on the compound action potential (NAP) or on the brain-stem potentials (Pot. II-V), but sedation improves significantly the signal-to-noise ratio, therefore we sedate all patients when registering the five early acoustically evoked potentials.

Acoustic Stimulation↗
PubMed1977

[Registration of the early acoustically evoked potentials using monaural and binaural stimulation (author's transl)].

At seven normally hearing test persons the early acoustically evoked potentials were registered using monaural, binaural and contralateral click-stimulation with a repetition-rate of 10/sec at the intensities of 90 and 70 dB SPL. In comparison to the monaural stimulation the binaural stimulation yields in the mean no significant alteration of the potentials I, II and III at both intensities. The mean enlargement of potential IV by binaural stimulation amounts to about 40% and is highly significant, but this advantage does not apply always to everybody: the factor of magnification of potential IV covers the range from one to two. The average increase of 66% at potential V is weakly significant for the intensity of 90 dB SPL. As expected from the results of contralateral stimulation the registrations at patients suffering from unilateral hearing impairment show on both sides the potential's threshold of the better hearing ear when stimulating binaurally; therefore you cannot determine the better cochlea. In addition to this fact the binaural stimulation of patients suffering from an acoustic neuroma removes the diagnostically important tool to recognize differences between the two sides. These findings are demonstrated by examples. Since it is impossible to predict an increase of the amplitude in the individual case and since there are serious diagnostic disadvantages, we don't deem advisable a binaural stimulation.

Acoustic Stimulation↗
PubMed1977

[Preparation and processing of clinical ERA-datas using a small laboratory computer: tentative experiences and results for the late, acoustically evoked potential N1 (author's transl)].

The efficacy of the Electric Response Audiometry (ERA) in the supraliminal range can be enlarged and improved by the use of laboratory computers. The acoustic system has to be described as objectively as possible from the lot of datas resulting especially from clinical examinations. An off-line-program sequence which may be routinely used, was elaborated for the laboratory computer PDP 12 in order to measure and evaluate the late, acoustically evoked potential N1. In addition to the organisation and documentation of the datas it is shown that for many cases the described and performed preparation and processing of the datas yield qualitatively and quantitatively better results.

Acoustic Stimulation↗
PubMed1976

Input-output function and adaptation behaviour of the five early potentials registered with the earlobe-vertex pick-up.

At twenty-three 20-30-year-old normal-hearing subjects the characteristic curves of amplitudes and latencies of the five early potentials, appearing within the first 8 ms after stimulus onset, were obtained. The potentials were registered with the earlobe-vertex pick-up, as described by Sohmer and with click stumulus rates of 5/sec, 10/sec and 100/sec; It could be seen: All five potentials depend in amplitude and latency on intensity; all potentials show with increasing click rate an adaptation and a delayed latency, when increasing the click rate from 10/sec to 50/sec; the adaptation phenomenon of the 1st, 2nd, 3rd and 4th potential is the most prominent, the 4th potential shows the smallest adaptation effect; the characteristic curve at 10/sec of the 1st and 3rd potential demonstrates a break at 70 dB SPL; the latencies of the five potentials begin to increase at click rates higher than 10/sec; the 4th potential seems to be the most suitable one for measuring the acoustical threshold; only the fifth potential diminishes in amplitude and increases in latency after administration of an anaesthetic, but an additional relaxant does not alter it any more.

Acoustic Stimulation↗
PubMed1975

[Age-dependent electric response audiometry (ERA)-findings in correlation with speech development (author's transl)].

The occurrence of periods of speech-certainty and speech-uncertainty can be observed in normal as well as in children impaired with hearing, voice and speech defects. This behaviour of voice and speech development has not yet been explained by subjective pure-tone or speech audiometry. 19 normal children were grouped into four age populations according to electroglotto- and phonographic analysis. This collective was then examined by Electric Response Audiometry (ERA) at the frequencies of 0.5 kHz, 1.0 kHz, 2.0 kHz, and 4.0 kHz. Speech-certainty was observed at a mean age of 4.5 years (Group II) and 6.5 years (Group IV), whereas speech-uncertainty was found at a mean age of 2.5 years (Group I) and 5.5 years (Group III). The supraliminal ERA results of contralteral pickup were evaluated in amplitude and in behaviour of latency. Because of the variety of ERA-characteristics, the age-dependent and frequency-specific development of the acoustic system is figured by integration below the characteristics in the supraliminal range. The mathematical result shows two opposite regions as well as the "hearing dynamic" as at the "dynamic of the behaviour of latency": a low-frequency region of 0.5 and 1.0 kHz and a high-frequency region of 2.0 and 4.0 kHz. Evaluation of the electroglottograms following Fourier's analysis shows a typical amplitude spectrum at speech-certainty and at speech-uncertainty.

Age Factors↗
PubMed1975

[Electrocochleographic potential pattern, recorded by different pick-ups (author's transl)].

At electrocochleography, the active electrode was placed on the earlobe, the mastoid, the nasopharynx, the hard palate and the external ear-canal respectively. It could be shown that the potential pattern, consisting of five components, during the first 8 msec after the click-onset could be obtained from all the above mentioned sites. In relation to the various electrode pick-ups we obtained different amplitude functions with nearly the same latency behaviour for all five potentials.

Acoustic Stimulation↗