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Biomedical subjects

M Walger

Publications and source records attributed to M Walger.

At least 37 records · Page 2Linked to original sources
PubMed1998

Epidemiology and etiology of acquired hearing disorders in childhood in the Cologne area.

Because of their serious consequences for all aspects of development, severe hearing disorders in children are an important clinical entity. A better understanding of the epidemiology and etiology of acquired hearing disorders may potentially lead to more effective prevention. Marked differences in the epidemiology of acquired hearing disorders are reported in the literature. In order to illuminate the problem of acquired disorders and to define current etiological causes with special regard to ethnological factors in the Cologne area, we started a retrospective study. A total of 314 children in residence at the school for hearing impaired children in Cologne were investigated. We also obtained concise data on the structure of the population in order to determine prevalence of acquired hearing disorders in the German and immigrant portions of the population. We found an overall prevalence of 0.43 per thousand for severe hearing disorders and deafness. German children were most frequently affected by acquired, and non-German children by hereditary hearing disorders. The most common causes of acquired severe hearing disorder were the perinatal complex of premature delivery, anoxia and hyperbilirubinuria or kernicterus. Other causes were congenital rubella infections and meningitis in early childhood. The accumulation of perinatal etiologies seems to be the reason for the remarkable majority of acquired hearing disorders among German children. One reason might be progress in neonatology which exerts two effects. It decreases perinatal mortality but increases perinatal complications like acquired hearing impairment. The incidence of congenital rubella in Germany has decreased during recent years, reaching a low level.

Child↗
PubMed1998

[Measuring vibration properties of middle ear implants with the mechanical middle ear model. Initial results].

With the aid of a mechanical middle ear model (MMM) the sound transmission properties of different middle ear implants were investigated. Input of the MMM involved a broad-band signal from 100 to 5000 Hz that was supplied by a miniaturized loudspeaker. Displacement of an artificial stapes footplate was measured by a fiberoptic probe. The transfer functions of four different total ossicular replacement prostheses (TORPs) of different materials and shapes were compared. Three of the devices revealed similar transfer functions which corresponded to the typical curve of the normal middle ear. One of the prostheses demonstrated a high-frequency deterioration of approximately 5 dB. This effect was explained by a 3- to 6-times higher mass of the implant when compared to the others. Altogether, the weight of the prosthesis seems to have the most marked impact on sound transmission to the inner ear, whereas stiffness of the implant itself is less crucial as long as it can be regarded as a rigid body.

Acoustic Impedance Tests↗
PubMed1998

[Etiology of moderate and profound deafness in childhood].

UNLABELLED: The present study sought to determine the etiology of bilateral profound hearing losses in children living in Germany. Additionally, a comparison with the data of previous investigations in the available literature was used to update causes now known through medical progress. PATIENTS AND METHODS: The medical charts of 314 profoundly hearing-impaired pupils at schools for the deaf in Cologne, Germany, were reviewed. All available data on possible etiological factors were collected. In addition, the families of these children were interviewed using a standardized questionnaire. RESULTS: Sixty children were found to have bilateral sensorineural hearing losses averaging 30 to 60dBHL within the frequency ranges of 500-2000 HZ, while 254 had bilateral hearing impairments of 60 dBHL or greater. The etiology of the hearing disorder could be determined in 218 of the children. Eighty-two children suffered from hereditary deafness and 136 from acquired hearing losses. The etiology could not be determined in 96 children. Hereditary causes included 34 children with mendelian autosomal dominant losses, 46 with autosomal recessive losses and two children with genetic but non-mendelian causes. Immigrants to Germany (mostly from Turkey and the former Soviet Union) were found significantly more frequently among the students of these schools, than among the total population of the Cologne area. In this group of students, autosomal recessive deafness was particularly common as compared to the overall native population. Acquired hearing disorders were broken down into three subgroups: prenatal, perinatal and postnatal disorders. A prenatal etiology was considered in 32 children, 21 of whom had known congenital rubella infection. This entity was significantly less common among younger children. A perinatal etiology was considered in 60 children. Causative factors were birth asphyxia, apnea and/or hyperbilirubinemia. Forty-four children had deafness attributed to postnatal causes, with bacterial meningitis (n = 31) being the most important single factor. The findings reported indicate changing trends for causes of hearing loss in children with severe hearing impairment in Germany.

Adolescent↗
PubMed1997

[A registration system for evaluating acusto-mechanical transmission of middle ear implants].

A measurement system was developed that permits objective comparisons of the sound conduction of middle ear implants. The implants are fitted into a mechanical middle ear model which approximates the impedances of the eardrum and the inner ear. A defined signal within the frequency range of 0-5 kHz is provided by a miniaturized loudspeaker at the input to the model and is measured by a probe microphone. Displacement of an artificial stapes footplate at the output of the model is measured by a fiberoptic probe with a sensitivity of 5 nm. The transmission function is calculated as the quotient of the output and the input signal. This system can be used to evaluate the sound-transmitting properties of different middle ear implants excepting other influences, such as surgical techniques. This work details the measurement system and demonstrates basic influences on the sound-transmission of middle ear implants.

Acoustic Impedance Tests↗
PubMed1997

[Effectiveness of partial and complete instrumental masking in chronic tinnitus. Studies with reference to retraining therapy].

Jastreboff und Hazell [9] developed a neurophysiological approach to tinnitus perception, including the important role of the central nervous system in the maintenance and intrusiveness of tinnitus. They introduced tinnitus-retraining therapy, consisting of four different strategies: (1) directive and person-centered counseling; (2) hearing aids and/or noise generators and/or environmental sounds; (3) psychological therapy; (4) adjacent therapies. Tinnitus should not be masked as with a tinnitus-masker, but must be able to be heard in addition to the noise! A noise generator or hearing aid should be worn at least 6-8 h per day over a period of up to 18 months. In additions several clinical visits are required in order to reinforce the counseling. The actual results show complete tinnitus remission for about 20-30% and partial remission for 50-60% of the patients [6]. We report on a retrospective study in patients wearing hearing aids or tinnitus-maskers over a period of 3 years. We compared the results of patients using partial tinnitus masking to those using complete masking. The tinnitus-related and general psychological complaints were acquired by the 52-item tinnitus questionnaire developed by Hallam et al. [4] and modified by Goebel and Hiller [3]. To describe the dimensions of tinnitus-related distress the scales are labelled emotional distress, cognitive distress, emotional and cognitive distress, intrusiveness, auditory perceptual difficulties, sleep disturbance and somatic complaints. Positive changes for the global tinnitus questionnaire score of more than 10 points are significant in the dimensions of tinnitus-related distress and are described as partial tinnitus-reduction. The group with partial masking effects can be compared to those performing retraining therapy to day because directive and personal centered counseling were integrated for all patients. Patients reporting partial masking effects through their aids (hearing aid or noise generator) showed more effective treatment results (reduced or disappeared tinnitus) than those using complete masking effects (P < 0.05). The reported results are improved by current investigations in Germany showing about 20-30% tinnitus remission and 50-60% significant reduction after 1 year of treatment [1]. Further scientific investigations must be carried out to evaluate the appropriateness and effectiveness of the retraining therapy and with regard to unique quality standards.

Cognitive Behavioral Therapy↗
PubMed1997

[No evidence for hearing aid-induced progressive pediatric hearing loss in the Cologne region].

Progressive hearing loss during childhood caused by a hearing-aid induced deterioration has been discussed controversely since 1939. However, it is unchallenged that in cases of profound sensorineural hearing loss in infancy and early childhood powerful hearing aids are necessary for auditory and speech development. Due to an increase of progressive hearing losses during the last 4 years, we discussed the possible causes and the probability of hearing aid induced progressions once more. Our study consists of two investigations: First, all patients since 1993 suffering from progressive hearing loss among all hearing impaired children in the department of Audiology and Pedaudiology of the ENT-Hospital of Cologne were taken into account. Second, all children of the Rheinische school for hearing impaired children were investigated. The evaluated data included the degree of severity and etiology of the hearing loss, the duration of the hearing aids use and the amplification of the hearing aid. 23 children were diagnosed with a progressive hearing loss in the period. We observed a massive increase over these years. No correlation between the duration of the hearing aid usage and the maximum output level was found. Furthermore, there was no difference between the causes of the hearing losses between the children of the school and the children with progressive hearing loss. At the moment, we do not see any reason to change our strategy for fitting hearing aids. The increase of progressive cases in the last 2 years should be the reason for further investigations in this field.

Adolescent↗
PubMed1997

Ontogeny of electrically evoked brain stem potentials in neonatally deafened gerbils (Meriones unguiculatus) after cochlear implantation.

To investigate the ontogeny of the electrically evoked auditory brainstem response (E-ABR) we used an animal model of neonatally deafened gerbils with an intracochlear implanted electrode. The E-ABR were recorded in three groups: normal hearing animals (NORM) and binaural deafened without chronical electrostimulation (BD) in comparison to binaural deafened animals with chronical stimulation (BDS). In group BD the deafening lead to inter-peak-latency II-V increase and histological degeneration in the Cochlear Nucleus. In chronical stimulated animals (BDS) we could not observe significant differences compared to unstimulated gerbils until the day after birth. In further studies longer stimulation periods, recordings of electrically evoked middle latency response as well as histological examinations of more central parts of the auditory pathway will be included.

Animals↗
PubMed1997

Meriones unguiculatus (Gerbil) as an animal model for the ontogenetic cochlear implant research.

The rehabilitation of prelingually deafened children using cochlear implants still raises several basic problems, e.g. growth of the skull and maturation of the auditory system. Systematic research in these problems requires a reliable animal model. The gerbil (Meriones unguiculatus) was investigated in respect of its suitability as an animal model for ontogenetic cochlear implant research. Gerbil pups were deafened by a single intracochlear application of neomycine on their 14th day after birth before the onset of natural hearing and implanted with an animal specific cochlea implant at day 30 after birth. To maintain the biological relevance the social sounds of gerbils were frequency transformed and used in daily electrostimulation until the 90th day after birth. As well established animal in hearing research the gerbil appears to be an appropriate animal model for ontogenetic cochlear implant research.

Animals↗
PubMed1994

[Sense of smell in deaf and blind patients].

The olfactory performances of 10 visually-impaired and 9 hearing-impaired subjects were investigated by a psychophysical sniffing test (the Munich Olfaction Test). These subjects were compared with 21 control volunteers who completed the test with covered eyes, 20 control volunteers whose ears were plugged during the test and with 22 unimpaired controls. The test examined discrimination performances, detection and perception thresholds, identification abilities, olfactory memory, and hedonistic evaluations of all subjects. The present results showed that attention focusing on olfactory tasks by lowering of auditory or visual inputs did not enhance the olfactory performances of the control subjects. Also, the visually-impaired subjects did not perform better then the control subjects. The diminished olfactory abilities of the hearing-impaired were discussed against the background of delayed language acquisition.

Adult↗
PubMed1993

Maturation of auditory evoked potentials in young guinea pigs with binaural conductive hearing loss.

A reversible conductive hearing loss produced during the first 4 weeks post partum caused marked alterations in the development of click-evoked auditory brainstem (ABR) and middle latency (MLR) responses in guinea pigs. The early component PI in the ABR in controls showed adult-like latencies at the time of birth, while the later ABR components PIII and PV and all components investigated in the MLR showed postnatal development characterized by a shortened latency that persisted for the whole period of investigation. The course of the ABR latencies showed the sharpest decrease during the first 2-3 weeks of life, while that for the MLR took place during the first 5 weeks. In addition to the increased ABR thresholds and lengthened ABR latencies due to the conductive hearing loss, development of the ABR inter-peak latencies (IPL) and MLR latencies was retarded. The IPL reached control values 1 week after the end of the deprivation phase, while the delay in MLR started later (4th week) and lasted longer than did that in the ABR. These findings showed that a long-lasting postnatal conductive hearing loss does not generate sustained impairment at the level of the brainstem but can evoke longer-lasting deficiencies at higher stations of the auditory pathway.

Aging↗
PubMed1993

Plastination: a new approach to morphological research and instruction with excised larynges.

Impregnation of biologic materials with curable polymer (plastination) allows wider use of human tissue for both basic and clinical research and instruction. The aim of this study was to determine for the first time the potential of this method in the field of laryngology. A feasibility study on 54 pig larynges established a detailed methodology for larynx plastination and determined the extent of shrinkage by using computer-assisted morphometry. The process involves dehydration, saturation with an appropriate intermediate solvent, and infiltration with cured polymer in vacuo. In the main study 20 fresh, intact human larynges and 12 laryngectomy specimens were submitted to plastination. The resulting resin blocks were cut with a diamond band saw into 0.8-mm sections in the transaxial plane. The resulting specimens are dry, odorless, and durable, and do not deteriorate with time. The subtle features of soft tissue pathology are well preserved. Shrinkage of plastinated larynges is less than 10%. The complete process is accomplished within 5 weeks. Staining of sections with toluidine blue provides an enhanced contrast between different types of tissue, allowing a clear identification of tumor invasion. Plastination is considerably faster than celloidin embedding and causes minor anatomic changes. It provides durable specimens of high quality for teaching purposes. In research, it allows the investigation of all tissue components in their undisturbed context in the borderline area between gross anatomy and histology.

Anatomy↗
PubMed1992

Maturation of binaural interaction components in auditory brainstem responses of young guinea pigs with monaural or binaural conductive hearing loss.

Reversible conductive hearing loss created during the first 4 weeks post partum caused marked alterations in the maturation of binaural interaction components in the auditory brainstem responses of guinea pigs. In untreated control animals all three components investigated demonstrated postnatal development in terms of latency shortening that was completed during the first 3 weeks of life. Plugging of both external ear canals caused a significant delay in the maturation of the late component DN2, where latency values of the controls were reached only 2 weeks after the end of the treatment, i.e. after 6 weeks of life. Monaural deprivation likewise led to a retarded development of peak latencies during the phase of imbalanced sensory input. After the end of the one-sided conductive hearing loss the maturation process was markedly enhanced, even resulting in latency values for DN2 and DP1 that were significantly shorter than those of the controls. This phenomenon persisted until the end of the study period and was the case for both plugged and untreated ears in this group of animals. The time course of latencies in two other groups of experimental animals which were deprived in the same way as adults suggests that the effects observed are due to a sensitive period in the maturation process of the auditory pathway.

Age Factors↗
PubMed1989

[Effect of binaural conductive hearing loss on maturation of acoustically evoked potentials (auditory brain stem response, middle latency response) in guinea pigs].

During the early development of the acoustic system a conductive hearing loss may alter the maturation of acoustically evoked potentials and affect the development of hearing. The present experiments were carried out in newborn guinea pigs with binaural conductive hearing loss. The external ear canals were plugged over a period of one month from the first day postpartum. During and after deprivation click-evoked Auditory Brainstem Responses (ABR) and Middle Latency Responses (MLR) were collected to analyze changes in the maturation of these potentials in comparison to untreated animals. This type of deprivation is characterized by threshold elevations of about 40 dB over a wide frequency range. In young deprived animals, ABR Latencies (PIII, PV) and interpeak latencies exhibited a significant delay with a maximum between day 13 and 19, which disappeared within 10 days after the end of the treatment. MLR latencies were also significantly affected after three to four weeks of the deprivation phase. In contrast to the ABR, the recovery of the latencies was completed within four to six weeks. These results therefore indicate that a conductive hearing loss may alter the maturation of the acoustically evoked responses in the sensitive phase after birth. This type of partial deprivation may affect the development of hearing and speech perception in children with chronically occurring otitis media.

Age Factors↗
PubMed1987

Short-time course of adaptation pattern after noise exposure: electrophysiological studies in man.

Tone burst and click-evoked potentials were recorded in both humans and guinea pigs to determine whether responses associated with the cochlea and brainstem regions show a pattern of recovery from noise exposure similar to the polyphasic changes found for the pattern of early recovery from temporary threshold shift reported by Hirsh and Ward in 1952 [J. Acoust. Soc. Am. 24, p. 131]. During the 'post-stimulatory' phase following exposure for 5 min to broad-band noise at various intensity levels between 90 and 110 dB SPL, changes in amplitude and latency of the dominant complexes of the cortical and brainstem-evoked potentials were monitored for 5 min with 1.5- and 60-second time resolution. There was clear evidence of polyphasic processes at the cortical level, whereas in the brainstem region, large post-stimulatory amplitude shifts were generally accompanied by an asymptotic recovery. The relevance of the results to the different stations in the auditory pathway is evaluated by comparison with published electrophysiological data on activities at the different levels of the brainstem and the brain as reflected in evoked responses and single-unit recordings.

Adaptation, Physiological↗
PubMed1985

The influence of moderate-intensity noise on the click-evoked compound action potential of the guinea pig, Cavia porcellus.

Noise-induced alterations of the click-evoked compound potential (CAP) were studied by means of electrodes chronically implanted near the round window in 15 pigmented guinea pigs aged 3-6 months. The potentials were recorded before, during and after exposure to continuous pink noise maintained at an intensity of 80, 90 or 100 dB SPL for 120 h. During the exposure phase the CAP thresholds of all the animals tested increased exponentially, nearly leveling out by approximately 48 h to form an asymptotic threshold shift. Recovery after the end of exposure also occurred exponentially, with a return to the original threshold for neural excitation after at most 72 h. There was no detectable change in amplitude, latency or inter-peak interval of the CAP when correlated with the change in threshold.

Acoustic Stimulation↗