[Diagnosis of endolymphatic hydrops using low frequency modulated distortion product otoacoustic emissions]. / Diagnostik des endolymphatischen Hydrops mit tieftonmodulierten DPOAE.

BACKGROUND: The low frequency modulation of distortion product otoacoustic emissions (DPOAEs) is an objective audiometric method that appears to be a useful tool for the diagnosis of endolymphatic hydrops (EH), e.g. in patients with Menière's disease, or in those who present only some of the symptoms of the disease. METHOD: Low-frequency modulated DPOAEs were registered in 20 patients with unilateral Menière's disease (13 women and 7 men, aged 40-66 years) and were compared to a control group matched in age and gender. As a diagnostic parameter, the 'modulation index' MI=1/2 MS/DM was used (MS or modulation span, being the difference between the maximal and the minimal DPOAE-amplitude, and DM, being the mean of the suppressed stationary DPOAE-amplitude). RESULTS: In the patients with unilateral Menière's disease, MI was lower than in the control group. This difference was highly significant. In 56% of the patients' contralateral ears MI was lower than the cut off-value and significantly lower than in the control group, but did not differ significantly from the patients' ipsilateral ears. CONCLUSION: The registration of low-frequency modulated DPOAEs is comparable to the generally applied transtympanic electrocochleography in its diagnostic validity. The method is fast and non-invasive and could be applied to monitor the course of the disease.

[Aural fullness and endolymphatic hydrops]. / Druckgefühl im Ohr bei endolymphatischem Hydrops.

BACKGROUND: Low-frequency modulated DPOAEs were registrated to investigate whether the subjective symptom of aural fullness can indicate an endolymphatic hydrops. METHOD: The cochlear partition is periodically moved towards scala vestibuli and scala tympani by a low-frequency suppressor tone. The level of simultaneously registrated DPOAEs is modulated depending on the phase of the suppressor. This modulation may be reduced when the displacement of the organ of Corti is inhibited by mechanical stiffening of the basilar membrane (e. g. in endolymphatic hydrops). SUBJECTS: Low-frequency modulated DPOAEs were registrated in 15 patients with Menière's disease, in 8 patients with aural fullness and tinnitus, but without vertigo, and in 21 normal hearing adults. RESULTS: In both patient groups the modulation depth is high significantly lower than in the control group. The results do not differ significantly in the patients with and without vertigo. CONCLUSION: The reduction of the modulation depth can be interpreted as a sign of an endolymphatic hydrops. In the group of patients with aural fullness a cochlear hydrops can be assumed. The measurement of low-frequency modulated DPOAEs is a new tool to diagnose and monitor the course of endolymphatic hydrops and to evaluate the effectiveness of therapeutic methods.

[Objective test of smell with cognitive potentials]. / Objektiver Riechtest mit kognitiven Potenzialen.

BACKGROUND: An objective smelling test is indicated for a reliable assessment of olfactory disorders. Usually olfactory evoked potentials (OEP) are registered. But the technique of this measurement is complicated and the generation of the OEP depends on the respiration of the subject. Alternatively, the contingent negative variation (CNV) can be used in the diagnosis of anosmia and parosmia, requiring only a simple olfactory stimulator. SUBJECTS AND METHOD: OEP and CNV were derived from 25 adults with normal smelling and from 16 patients with anosmia after head injury. First, the "direct" CNV was registered when the subjects expected a tone following a smell stimulus after 1.5 s. Using two different odors in a random order, the tone only followed one of them, so the "selective" CNV was scored. RESULTS: In both tests a distinct CNV was found in 21 and 23 normal smelling subjects, respectively. OEPs were absent in 4.3 % of this control group. No patient with anosmia showed an OEP or a CNV. The amplitudes of the "selective" CNV are significantly higher than those of the "direct" CNV. No gender dependency was found. CONCLUSION: The results show that an objective olfactometry can be realized by registration of CNV. Contrary to the measurement of OEP which depend on the physical parameters of olfactory stimuli, CNV correlates well with the cognitive identification of odor.

[Electrocochleography and phase audiometry in diagnosis of Meniere disease]. / Elektrokochleographie und Phasenaudiometrie zur Diagnostik des Morbus Menière.

The diagnosis of Menière's disease is uncertain when the typical symptoms do not occur completely and definitely. A reliable finding of an endolymphatic hydrops (EH) is the base for a correct prognosis and therapy. Electrocochleography is a proven diagnostic procedure but requires a lot of time and of technical know-how. The mobility of cochlear partition can be tested by low-frequency masking (LFM) recording the phase dependent subjective masked threshold of a short test tone. We performed electrocochleography and LFM in 29 patients with suspected Menière's disease at the same day. Both tests pointed at an EH in 62%, and in 24% the results showed correspondent negative results. In 14% the results were inconsistent. Both methods also showed in 59% of the contralateral ears without symptomatic signs the indication of an EH. Considering the good conformity of both tests the easier LFM can be recommended for detection of EH.

Phase-dependent suppression of transient evoked and distortion product otoacoustic emissions by a low-frequency tone.

The subjective recording of the masked threshold of short acoustical stimuli with a loud tone of 30 Hz (phase audiogram) has been used for the clinical diagnosis of endolymphatic hydrops (EH). In normally-hearing subjects, a marked modulation of the threshold was found, depending on the phase of the low-frequency tone. A very small dependence was found in patients with Menière's disease, due to the micromechanical changes in the basilar membrane (BM). The same phase relationship becomes apparent in low-frequency suppression of otoacoustic emissions. The amplitudes of TEOAEs are controlled by the phase-dependent displacement of the BM. The suppressed TEOAEs have to be measured separately in each phase relationship. During recording of suppressed DPOAEs, the low-frequency suppressor is permanently superimposed on the pair of primary tones. After time averaging and a moving short-time FFT, the spectral values of the DPOAEs are obtained depending on the phase of the low-frequency tone. Modulation depends also on the masker level, the levels of the primary tones, and on their frequency range. The method of low-frequency suppressed DPOAEs is an objective method to diagnose EH and could be a useful tool in human inner ear research.

Low-frequency modulation of the 2f1-f2 distortion product otoacoustic emissions in the human ear.

Low-frequency masking is a recent clinical procedure for the differential diagnosis of sensory hearing loss. Currently this requires the recording of the phase-dependent masked subjective threshold, which is time consuming and not always accurate. As an objective method, the recording of modulated distortion product otoacoustic emissions (DPOAEs) can be performed continuously, and with better frequency specificity. Results of measurements of the low-frequency modulated two-tone DPOAE 2f1-f2 in the human ear, and its dependence on various acoustic parameters, are presented here for the first time. Similar to the masked hearing threshold, the pattern of the phase-dependent modulated DPOAEs displayed two minima, at the phases of maximal rarefaction and condensation, respectively, with a latency of about 4 ms (suppressor frequency 32.8 Hz). The smaller dip, at maximal condensation, appeared only for a high suppressor level, and for a low level of the primary tone f2. The modulating effect measured for the primary frequencies f1 = 2.5 kHz and f2 = 3 kHz, decreased for 4 and 4.8 kHz, and vanished for 5 and 6 kHz. The results are discussed using a cubic distortion model based on the Boltzmann function for mechano-electrical transduction of the hair cells. The saturation behavior of the increase of the DPOAE level at different phases is compared with the growth rates of the DPOAE level in normal hearing and in sensory hearing loss.

[Frequency specificity of acoustic evoked potentials of early and intermediate latency with high-pass noise masking]. / Untersuchung der Frequenzspezifität akustisch evozierter Potentiale früher und mittlerer Latenz mit Hochpassmaskierung.

In contrast to auditory brainstem potentials (ABR), a more apically defined generation of middle latency evoked potentials (MLR) can be assumed due to the longer integration time present. To date, the effect of stimulus frequency spectra on MLR has not been completely known. By using masking with high-pass filtered white noise in 12 normal-hearing adults, we measured the dependence of amplitude and latency of ABR and MLR on filter frequency. No differences were found between the masking effects for ABR and MLR evoked by tone bursts of 0.5 and 2 kHz. The high-pass masking of click stimuli showed a greater influence on the amplitude and latency of the ABR than on MLR. These different qualities have to be considered clinically when evaluating the methods and results of hearing testing with acoustic evoked potentials. Our findings show that MLR evoked by tone bursts should be used for the frequency selective diagnosis of hearing thresholds, especially in low-frequency ranges.

Low-frequency masking for detection of endolymphatic hydrops in patients with glaucoma.

The coincidence of various eye and ear abnormalities has been described in the literature. Some authors discuss the possible existence of endolymphatic hydrops in patients with glaucoma. Whereas the current diagnostic tests for glaucoma are well-defined and evident, those for endolymphatic hydrops are not so reliable. This has made it difficult to accurately study the coincidence of endolymphatic hydrops and glaucoma. For better detection of endolymphatic hydrops, we performed low-frequency masking tests in 23 patients with primary open-angle glaucoma without signs of Ménìere's disease. The phase dependent sensitivity of the organ of Corti to a short test stimulus can be measured by applying a low-frequency masker tone to determine the modulation depth. Whereas the modulation depth in the normal hearing population is around 20-35 dB, the modulation depth in patients with Ménière's disease may be significantly decreased (5-10 dB), depending on the stage of disease. A decreased modulation depth was found in at least one ear in 19 of our 23 patients with glaucoma. Correlations between homeostatic mechanisms and their histological characteristics, e.g. melanocytes and their hormonal and enzymatic regulation, will be discussed. If the common pathogenesis of eye and ear lesions is better understood, it may be possible to develop new and more effective strategies for prevention and therapy.

Diagnosis of endolymphatic hydrops by low-frequency masking.

Low-frequency masking is a new method for the diagnosis of endolymphatic hydrops. A short acoustic stimulus and a low-frequency masker tone are applied to the same ear in an adjustable phase relationship. We recorded phase-dependent masked thresholds from normal-hearing subjects, and patients with Ménière's disease and sensory hearing loss without vertigo. In normal hearing, there is a mean maximal difference in masking (modulation depth) of 28 dB between the phase delays of 0 degree and 270 degrees. In patients with sensory hearing loss without vertigo, modulation depth is reduced due to recruitment. In Ménière cases, the phase dependence may be totally absent and varies as the disease progresses. Therefore, repeated measurements of masking are required: patients and subjects with normal hearing were tested for a period of 1 year. Also, modulation depth is significantly reduced in the contralateral nonsymptomatic ears of Ménière patients. The results indicate that low-frequency masking is a quick, noninvasive and relevant method for the diagnosis of endolymphatic hydrops.

Impact of mechanical heart valve prosthesis sound on patients' quality of life.

BACKGROUND: The "click" sound of mechanical heart valve prostheses has been recognized as a disturbing factor for some patients after mechanical heart valve implantation. The factors determining the extent of disturbance remain controversial. METHODS: Ninety-five unmatched patients with six different valve types were examined (Duromedics-Edwards, Björk-Shiley, St. Jude Medical, Medtronic, CarboMedics, and Omnicarbon), including 12 patients with double-valve replacement. Three groups (Björk-Shiley, Duromedics-Edwards, and St. Jude Medical) were comparable in size. All patients were examined and interviewed, a hearing test was performed, and valve sounds were analyzed. Sound transmission was evaluated. RESULTS: The loudest valve was the Duromedics-Edwards prosthesis (mean, 84.2 dB[A] impulse) and the St. Jude Medical was the quietest (mean, 73.5 dB[A] impulse). This ranking was independent of patient variables and valve position. Discomfort level correlated with hearing loss and loudness of the valve. Patients desiring a quieter valve had better hearing, had louder valve sounds, felt disturbed by the sound, had partners who felt disturbed, and were receiving coumarin for anticoagulation. Sound was transmitted predominantly by air conduction. The frequency analysis to identify different valves was unsatisfactory, but louder frequencies did correspond with hearing-impaired patients' audiograms. CONCLUSIONS: Our results emphasize the need for valve design changes, preoperative education about the sound, and inclusion of routine hearing tests into the preoperative workup.

[Diagnosis of endolymphatic hydrops with low tone masked otoacoustic emissions]. / Diagnostik des endolymphatischen Hydrops mit tieftonmaskierten otoakustischen Emissionen.

BACKGROUND: A new method of diagnosis of endolymphatic hydrops by recording low-tone masked evoked otoacoustic emissions (TEOAE) is presented. METHODS: A short acoustic stimulus and a masker tone of 30 Hz are applied in an adjustable phase relation simultaneously to the same ear. In the normal hearing ear the masker shows little influence on the TEOAE at 0 degrees, whereas the suppression at phase 270 degrees (maximal rarefaction at the eardrum) is nearly complete. However, in cases of endolymphatic hydrops this masking effect is reduced or absent, indicating impaired mobility of the basilar membrane. RESULTS: The masked TEOAE were recorded of patients with normal hearing, Menière's disease, and sudden hearing loss without vertigo. In Menière cases with supposed endolymphatic hydrops, the amplitude modulation of the emissions was found to be much less than in the other groups. CONCLUSIONS: Where TEOAE can be recorded, low-tone masking is a quick, objective, and noninvasive method for the diagnosis of endolymphatic hydrops.

Masking and pitch shift of tone bursts and clicks by low-frequency tones.

From experiments in animals and investigations in humans it is known that the normally phase-dependent masking of a short stimulus by a low-frequency continuous tone does not occur in the case of endolymphatic hydrops. The recording of the masked threshold of short tone stimuli in a loud tone of 30 Hz is to be evaluated for the clinical diagnostics of Ménière's disease. To this purpose, the main parameters of the measurements (type, frequency, duration of the stimulus, and intensity of the masker) and their effect of phase-dependent masking and pitch-shift are investigated. Stimuli above 2 kHz are masked less than those of lower frequencies. Wide-band stimuli are less useful, since only the low-frequency component of their spectrum is masked. The tone stimuli should be short (1 - 2 ms) in order to make the measurement of the phase dependence more accurate. With increasing masker level the masking at phase 0 degree corresponds to the increase in level, at phase 270 degrees the amount is twice as much. The pitch shift which is perceived in low-tone masking depends on the phase of the stimulus, and on the levels of the stimulus and the masking tone. The use of brain stem recordings in the investigation of phase-dependent low tone masking is problematic since well-synchronizing stimuli with high frequency spectral components are masked poorly.

Sensory cortical processing and the biological basis of personality.

Action-oriented personality traits such as sensation seeking, extraversion, and impulsivity have been related to a pronounced amplitude increase of auditory evoked scalp potentials with increasing stimulus intensity. Dipole source analysis represents a crucial methodological progress in this context, because overlapping subcomponents of the scalp potentials can be separated and can be related to their generating cortical structures. In a study on 40 healthy subjects, it was found that sensation seeking is clearly related to the auditory evoked response pattern (N1/P2-component, stimulus intensities: 60, 70, 80, 90, 100 dB SPL) of the superior temporal plane including primary auditory cortex, but not to that of secondary auditory areas in the lateral temporal cortex. These results support the concept that the serotonergic brain system, which is supposed to modulate sensory processing in primary auditory cortices, is an important factor underlying individual differences in sensation seeking.

[Olfactory evoked potentials and contingent negative variation in expert assessment of disordered sense of smell]. / Olfaktorisch evozierte Potentiale (OEP) und Contingent Negative Variation (CNV) bei der Begutachtung von Riechstörungen.

Normally, the sense of smell is assessed by means of traditional subjective tests (sniff test, gustatory smell test, and trigeminus test). When results are inconclusive, an objective smell test is indicated. Simultaneously registering olfactory evoked potentials (OEP) and contingent negative variation (CNV) permits evaluation of both odor perception and odor discrimination. We can even objectively assess the false olfactory sensations in parosmia patients who are unable to discriminate between different odors. In this study, the results of 59 patients with olfactory disorders are presented. Head trauma and upper respiratory infections were the most common causes of the patients' complaints. In twelve cases, lack of cooperation and patient unrest prevented us from evaluating the data. In anosmia, the objective results agreed completely with the patient's subjective assessment. In hyposmia and parosmia, the results agreed with the patient's subjective assessment in most cases; here we were able to arrive at a more specific diagnosis in several cases. The objective smell test can be used to supplement subjective methods and thus provide more reliable assessment of olfactory disorders.

[Cepstrum analysis in voice disorders]. / Cepstrumanalyse bei Stimmerkrankungen.

Objective data and reproducible procedures are increasingly demanded for assessment and long-term comparison in voice disturbances. Well-known electroacoustic methods like formant analysis, autocorrelation and inverse filtering have been applied for this purpose, though without leaving experimental stage. The cepstrum analysis presented here permits an easy and distinct separation of glottal pitch and filter function of the vocal tract. In this study, 112 normal and hoarse voices were analyzed. The sum of amplitudes of the first cepstral pitch peaks differed significantly between the different degrees of hoarseness (0-3). Disturbances producing hoarseness, however, could not be sufficiently differentiated by the method in its present state.

Intensity dependence of auditory evoked dipole source activity.

The spatio-temporal approach of dipole source analysis represents a crucial methodological progress in research on individual differences in the dependence of auditory evoked potential amplitude on stimulus intensity (augmenting/reducing) because overlapping subcomponents of the N1/P2-component can be separated and can be related to their generating cortical structures. Basic aspects of the intensity dependence of auditory evoked dipole source activity were analysed in 40 healthy subjects. The evoked responses to binaural 1000-Hz tones at five levels of intensity (60, 70, 80, 90, 100 dB sound pressure level) were recorded at 33 sites across the scalp. The dipole source analysis of the grand average data confirms the reports in the literature that the N1/P2 potentials at the scalp can be explained by two dipoles per hemisphere: a tangential dipole, representing activity of the superior temporal cortex (including primary auditory cortex), and a radial dipole, representing activity of the lateral temporal cortex (secondary auditory areas). The intensity dependence of the tangential dipole activity was significantly more pronounced than that of the radial dipoles, supporting the assumption that radial and tangential dipoles represent different physiological processes. A high reliability of the intensity dependence of the tangential dipole (Pearson correlation: r = 0.88) was found when retesting the subjects after three weeks. Age was negatively correlated with the intensity dependence of the tangential dipole. Dipole source analysis proved to be a reliable method which allows, at least in part, to study separately the intensity dependence of the evoked responses from primary and secondary auditory cortices. This is of importance with regard to the hypothesis that the central serotonergic system modulates the intensity dependence of the evoked N1/P2-response of primary auditory cortex.

Olfactory evoked potentials and contingent negative variation simultaneously recorded for diagnosis of smell disorders.

Objective diagnosis of olfaction can be performed by registration of cortical olfactory evoked potentials (OEP) and of contingent negative variation (CNV). The CNV is a negative voltage developing at the vertex after discrimination of one of two smells while the patient is expecting a second stimulus. By an adequate procedure, including a long time window for averaging (2.56 seconds) with appropriate filters, the two tests can be performed simultaneously in a single session of less than 10 minutes. Anosmia is determinable by both OEP and CNV, although CNV shows less variability. On the other hand, CNV requires attention and some cooperation of the patient. Parosmia is accessible by CNV only; two odor qualities presented in random order have to be distinguished. Hyposmia can also be detected; just above the discrimination threshold, CNV amplitudes tend to be large--even enhanced--whereas OEP amplitudes may still be undetectable.

[Effect of decreased and lost high frequency hearing on latency of acoustically evoked brain stem reaction]. / Der Einfluss von Hochtonsenken und -abfällen auf die Latenz der akustisch evozierten Hirnstammreaktion.

The diagnosis of retrocochlear damage is supported by an increased latency difference between peak I and peak V. In case of high frequency hearing loss peak I is often hard to determine, and peak V latency may be shifted not only by neural delay, but also by missing basal hair cells. The amount of cochlear delay can be estimated by a procedure presented here. High frequency decay was simulated by steep high-pass noise masking. Peak V latency turned out to be established by the highest unaffected frequency components of the click stimulus. Thus, in case of a high frequency gap (with normalization towards higher frequencies) latency may be almost normal. In case of prolonged latency the amount ascribable to the cochlea may be rather precisely be estimated. If the whole lag is explained this way, unnecessary further diagnostics can be avoided.

Low-frequency masking of brainstem potentials.

The phase and intensity dependence of masking a click by a loud low-frequency tone was examined with brainstem potentials. Wave V latency is practically unaffected; its amplitude, however, is maximally suppressed at a phase of 270 degrees, i.e. rarefaction in the ear canal and basilar membrane displacement towards the scala tympani. Corresponding to subjective threshold, a minor suppression is also observed for the opposite deflection. In the phase of maximal suppression, wave V can be cancelled by a 30 Hz tone of 115 dB SPL up to click intensities of 40 dB HL. With cochlear damage, total suppression can be achieved at even higher click intensities as long as they are close to the subjective threshold. Low-frequency suppression is discussed as a tool applicable for early diagnosis of endolymphatic hydrops.