Search PubMed⌕ Search

Biomedical subjects

D Mrowinski

Publications and source records attributed to D Mrowinski.

At least 37 records · Page 2Linked to original sources
PubMed1989

[Brain stem evoked response audiometry study with a bone conduction receiver in atresia of the auditory canal and microtia].

Conductive hearing loss may be determined from the latency delay of the brainstem auditory evoked response Jewett V, if other reasons that may prolong latency are ruled out. Therefore it is important to determine the bone conduction threshold when examining infants. Two bone vibrators have been chosen, which, with the help of "inverse filtering", provide the possibility of a good sound conduction of the click stimulus and thus a measurement near the hearing threshold. When applying bone vibrators to infants it must be borne in mind, that the sound transfer is reduced because the cranial sutures are not yet closed. The measurement of bone conduction is suitable for securing the result of high-grade combined hearing defects. In two cases of atresia of the external auditory canal and microtia brainstem evoked response audiometry is presented with evaluation of both air and bone conduction.

Adult↗
PubMed1989

Auditory brain stem response monitoring during middle ear surgery.

Conductive hearing loss can be determined in the course of middle ear surgery by sound probe stimulation and simultaneous recording of auditory brain stem responses. Mechanical properties of the ossicular chain, usually judged subjectively by the surgeon's visual and tactile senses, can be quantified objectively. Thus, disarticulation of ossicles can be localized precisely, and fixation of the head of the malleus can be differentiated from stapes fixation. Moreover, the function of the reconstructed ossicular chain or prosthesis may be ascertained.

Audiometry, Evoked Response↗
PubMed1988

[Is measuring impedance following ear operations an aid in the analysis of postoperative sequelae?].

While the diagnostic value of pre-operative tympanometry is undisputed, there are very few publications on its application in postoperative control of sound conduction development. We measured otoadmittance several times after middle ear surgery in 42 cases. A significant increase of maximal admittance is found over a period of up to 24 months in case of tympanoplasty type I (16 cases, Fig. 1), and after stapedectomy (8 cases, Fig. 3). After a tympanoplasty of type III (Wullsteins classification) many tympanograms were flat, even in the follow-up examination, but a tendency to improvement can also be observed (Fig. 2). In none of the groups was hearing loss correlated with otoadmittance. Thus, tympanometry is not suitable for postoperative evaluation of conductive hearing loss. Nevertheless, our results indicate that the healing process after tympanoplasty modifies middle ear sound transmission for quite a long time.

Acoustic Impedance Tests↗
PubMed1987

Auditory brainstem responses to single-slope stimuli. The influence of steepness and polarity.

Click polarity has little influence on brainstem potentials. We applied an auditory stimulus similar to a step function generated in a closed acoustic system. The influence of stimulus onset steepness (comprising rise time and intensity) on wave V latency and amplitude was investigated. A remarkable latency prolongation was observed for condensation (C) compared with rarefaction (R), if a sharp bend at the foot of the slope was avoided. The C latency lag was nearly the amount of rise time. The effect can be explained by cochlear travel time. Wave V amplitude for R slopes was significantly enhanced. At high intensity and short rise time, it reached twice the values found with C slopes, or with clicks of either polarity. Although the explanations found are not yet satisfactory, a clinical application in cochlear diagnosis is predictable.

Adult↗
PubMed1986

A long-term study of hearing in children following neonatal hyperbilirubinemia.

We conducted a long-term study of 85 children with known transient neonatal hyperbilirubinemia to determine if their hearing had been affected. None of the children had neural symptoms such as kernicterus. The children ranged in age from birth to 9 months and were studied by means of brainstem evoked response audiometry (BERA). Thirty-four of the children were studied sequentially between 15 and 80 months after the initial examination. Our results showed that there was no significant correlation between serum bilirubin concentrations and BERA thresholds or latencies. These findings indicate that, unlike manifest cases of kernicterus, neonatal hyperbilirubinemia does not affect neonatal hearing when treated promptly.

Audiometry, Evoked Response↗
PubMed1985

Brainstem and cochlea potentials evoked by rarefaction and condensation single-slope stimuli. A preliminary report.

Influences of stimulus polarity on Jewett wave V are rather small when using clicks which produce two or more polarity changes within a short time interval. In order to separate pressure changes towards rarefaction (R) and towards condensation (C) we applied steep single-slope stimuli returning very slowly to baseline. Brainstem responses recorded from 8 human subjects differed markedly for R and C onset. Amplitudes were much higher for R than for C onset. The main C response was double-peaked with the first peak appearing about 0.5 ms earlier and the second, higher one, 1 ms later than the predominant R wave. The transition from single-slope to click stimulation was investigated by combining R and C slopes. For large time intervals, independent responses to either slope were observed. Down to an on/off interval of 1 ms, the on-response predominated. For still shorter intervals an equalization of R and C responses and a graduation towards click responses was found. Using the same stimuli, cochlear microphonics (CM) and compound action potentials (CAP) were recorded from 7 guinea pigs. The CM did not replicate the slow off-motion of the single-slope stimulus, but returned back to baseline after 0.6 ms. The C compared with R latency of the CAP (peak N1) was also delayed by 0.6 ms. This delay, and that of human peak V, may be explained by CAP initiation only by one direction of basilar membrane motion.

Acoustic Stimulation↗
PubMed1985

[Latency behavior of early acoustic evoked potentials in inner ear hearing loss].

In 101 patients suffering from sensory hearing loss the latency of the auditory evoked brain stem potentials was investigated. In case of minor and moderate pancochlear deafness latency is found to be within normal range. In severe pancochlear hearing loss above 80 dB latency is significantly delayed. In basocochlear hearing disorders the latency-delay is depending on the extent of the frequency loss and on the degree of pure tone threshold shift. If the patient is suffering from a high frequency hearing loss, normal latency will be found in the higher stimulus levels whereas within low levels latency tends to be delayed depending on the cut-off frequency. A general prolongation of latency across all sound pressure levels will take place in cases with steep forms of high frequency hearing loss. For the purpose of investigating the wave-I-latency we used an earcanal electrode in some patients. It can be shown, that in cochlear hearing disorders the latency of wave V is delayed to the same extent as the latency of wave V. After discussing model studies reference values of wave-V-delay as a function of the degree of high frequency disorders are listed

Audiometry, Pure-Tone↗
PubMed1984

Brain stem potentials evoked by binaural click stimuli with differences in interaural time and intensity.

Auditory-evoked brain stem potentials were recorded from 12 adults with normal hearing using click stimuli with differences in interaural time and intensity. Almost independent superimposed Jewett V peaks were produced, whose latency and amplitude depended on the parameters of the stimulus applied to either ear. This indicates that separate binaural information for the evaluation of sound source direction is still available at the brain stem level where wave V originates. We demonstrate that the normal nonlinear latency/intensity function may be responsible for the subjective compensation of time and intensity differences, since the well-known trading functions show similar intensity-dependent gradients.

Adult↗
PubMed1984

[Objective gustometry with adequate stimulation by registration of contingent negative variation].

Cortical evoked potentials require a steep and temporally reproduceable onset of sensory stimulation. As both items are difficult with gustatory stimuli, we tried to record the slow expectancy potential or "contingent negative variation" (CNV), which has turned out to be useful in objective olfactometry and speech audiometry. Sour, sweet, bitter or salty fluids were embedded in a water stream, which was sucked through a device well fitting to the tongue with holes at adequate locations. The negative vertex potential developped reproduceably between the recognition of taste and the acoustic signal, which could be expected only after one of the two alternatively offered gustatory stimuli. Clinical use of the method is demonstrated in a case of asymmetric loss of smell due to interruption of the chorda tympani during cholesteatoma operation. The CNV appeared only when stimulating the side of the tongue opposite to the ear operated on. In addition to the total or unilateral loss of taste, the ability to differentiate between two gustatory qualities can be diagnosed with an objective method, provided the patient cooperates by calm and attentive behaviour.

Contingent Negative Variation↗
PubMed1982

Diagnosis of abnormal hearing adaptation by brainstem potentials.

Adaptation of the human brainstem potentials was investigated using three types of stimulation: paired clicks, varied click rates, and a gap in a continuous tone. Brainstem responses to the second of a pair of clicks is hardly influenced by pathological adaptation. In patients with a normal subjective threshold decay (Carhart test) peak V latencies of the brainstem potential for high click rates and for the tone gap were within the normal range. For a threshold decay of more than 20 dB, latencies were significantly prolonged. In cases of an unlimited Békésy decay the brainstem response was missing for the tone gap stimulus. Fast rate and tone gap stimulation are suitable for a sensitive illustration of the threshold tone decay.

Adaptation, Physiological↗
PubMed1982

[Evoked response audiometry in circulatory disorders in the brainstem (author's transl)].

In the case of retrocochlear lesions evoked potentials from different stages of the auditory pathway were recorded. Four Patients with nearly normal hearing threshold and normal cortical potentials show reduced medium latency potentials show reduced medium latency potentials due to circulatory dysfunction in the brainstem. Desynchronisation effects on the brainstem level are completely compensated in the cortex. The damage of the auditory pathway could not be found by X-ray or other usual clinical methods. In the two cases described improvement under medical treatment can be demonstrated.

Audiometry↗
PubMed1981

[Olfactory stimulation and contingent negative variation (CNV) (author's transl)].

In addition to olfactory evoked responses (Fig. 1a) the vertex-negative voltage shift was registered in 20 normal adults. Fig. 2 shows this potential for an olfactory indicative stimulus followed by a tone burst or flash sequence, which are stopped by the test person's manual reaction. In Fig. 3 two alternating odorous stimuli are presented, one of which is followed by the tone. The selective expectancy wave is followed by the tone. The selective expectancy wave is only built up by the marked olfactory stimulus. For the first time CNV can be used as a clinical investigation tool to confirm central perception of odorous stimuli and furthermore to objectivate impaired central odour discrimination (parosmia).

Adult↗
PubMed1981

[Measurements of the acoustic reflex at variable static pressures (author's transl)].

Acoustic reflex measurements are made on thirty normal and three early stage otosclerotic ears at different static pressures in the ear canal and recorded as reflex-tympanogram at 200 Hz and 660 Hz probe-tone frequency. Acoustic reflexes were elicited contralaterally with a pure-tone stimulus at 2,000 Hz. This stimulus was chosen to avoid technical artifacts. An example of a normal acoustic reflex pattern as a function of variable static pressure is presented (Fig. 1). This record was made at 20 dB above the subjects reflex threshold, using 660 Hz probe-tone frequency. The reflex deflection of susceptance is positive up to pressures of plus or minus 50 mm H2O and then becomes negative. The reflex deflection of conductance is negative in the total range. A stiffened middle-ear system shows negative reflex deflection of both admittance components. The reflex-tympanograms (Fig. 2) show the admittance component curves as a function of variable static pressure with and without eliciting the acoustic reflex in case of a normal ear, using probe-tone frequencies of 220 Hz and 660 Hz at 10 dB and at 20 dB above the subjects reflex threshold. The reflex-tympanogram in case of an early stage otosclerotic ear shows negative reflex deflection of susceptance within the total pressure range indicating pathological stiffness (Fig. 3). The reflex related change of the dynamic properties was stimulated in a mathematical model of the middle-ear (Fig. 4). The measurements could be explained in a mathematical approach.

Audiometry↗
PubMed1981

[Medium-latency acoustically evoked brain potentials used for examination of the auditory pathway (author's transl)].

Potentials of the 10-15 ms latency range evoked by acoustic clicks and Gauss-shaped tone bursts habe been investigated in normal hearing adults, 20 patients with cochlear damages, and 6 cases of temporal lobe processes. Methods and results are compared to those of brain stem audiometry. Mean and standard latency ranges are calculated for the different peaks (Fig. 1). Amplitudes should be used only for side difference evaluation in the same patient, because of their big interindividual variation. In cases of profound high frequency hearing loss (Fig. 2) medium-latency potentials yield true threshold values in the low frequency range, where brainstem potentials are failing. The medium latency potentials show a substantial decrease of amplitude for stimuli contralateral to the damaged side (Fig. 3). So this method can be a functional hearing test to detect or at least suspect temporal damages.

Audiometry↗
PubMed1979

Chronic and acute transtentorial herniation with tumours of the posterior cranial fossa.

In patients with expanding lesions of the posterior fossa general hyper-reflexia (and bilateral latency shifts of auditory evoked brain stem potentials) have been noted as possible symptoms of chronic ascending transtentorial herniation. After ventricular tap, this chronic herniation may evolve into acute herniation with progressive reduction of consciousness which in our experience can only be survived by decompression of the compressed brain stem. The chronic transtentorial herniation is related morphologically to demyelination of the pyramidal tracts and the auditory pathways, whereas the acute transtentorial herniation is related to microcirculatory disturbances in the reticular formation of the mesencephalo-pontine junction.

Auditory Pathways↗