Astrid Foerst

Risk Factors for Auditory Neuropathy/Auditory Synaptopathy

Aims: It was the aim of this study to describe risk factors in auditory neuropathy/auditory synaptopathy (AN/AS). Methods: Between 1997 and 2005, we diagnosed 37 children with AN/AS. They underwent a critical chart review for risk factors and etiological coincidences in this idiosyncratic disorder. Results: Eighteen neonates had a history of prematurity and low birth weight. Hyperbilirubinaemia was present in 13 children. Three patients had evidence of infection during pregnancy, and AN/AS was associated with complex syndromal diseases in 2 cases. A congenital, familial pattern was seen in 2 siblings. Seven patients had idiopathic AN/AS. Conclusion: Rather than being a single etiological entity, AN/AS comprises a spectrum of risk factors and associated problems affecting the cochlea and the auditory pathway. This study shows that the majority of AN/AS in children is the result of perinatal problems and is not genetic in origin. Hyperbilirubinaemia is a common and etiologically significant finding in infants suffering from AN/AS. Thus, early hearing screening for AN/AS including transient evoked otoacoustic emissions and auditory brainstem response assessment among neonates with risk factors for AN/AS is crucial in order to better manage patients suffering from this disorder.

Diagnostik und Therapie der auditorischen Synaptopathie/Neuropathie

ZusammenfassungDie audiologische Konstellation von pathologischen frühen akustisch evozierten Potenzialen (fehlend, erhöhte Schwelle und gestörte Kurvenform) trotz nachweisbarer otoakustischer Emissionen geht häufig mit einer von schlechtem Sprachverständnis geprägten Schwerhörigkeit bzw. mit Taubheit einher. Diese als auditorische Neuropathie erstbeschriebene, heterogene Erkrankungsgruppe beinhaltet peripher-auditorische Störungen der synaptischen Schallkodierung durch innere Haarzellen (Synaptopathie) und/oder der Erregungsbildung und -weiterleitung im Hörnerv (Neuropathie). Dieses Konsensuspapier gibt aktuelle Hintergrundinformationen sowie Empfehlungen zur Diagnostik und Therapie im deutschsprachigen Raum. Es nimmt dabei Bezug auf aktuelle internationale Statements.AbstractPathological auditory brainstem responses (lack of responses, elevated thresholds and perturbed waveforms) in combination with present otoacoustic emissions are typical audiometric findings in patients with a hearing impairment that particularly affects speech comprehension or complete deafness. This heterogenous group of disorders first described as “auditory neuropathy” includes dysfunction of peripheral synaptic coding of sound by inner hair cells (synaptopathy) and/or of the generation and propagation of action potentials in the auditory nerve (neuropathy). This joint statement provides prevailing background information as well as recommendations on diagnosis and treatment. The statement focuses on the handling in the german language area but also refers to current international statements.

Hearing loss in early infancy affects maturation of the auditory pathway

The influence of early cochlear hearing loss on maturation of the auditory pathway was studied by measuring auditory brainstem responses (ABR). In a retrospective study, 85 children with normal hearing (46 males, 39 females; age range 2 months to 14 years) and 165 children with binaural cochlear hearing impairment (89 males, 76 females; age range 1 month to 16 years) were examined. A significant positive correlation (p<0.001) between the degree of hearing loss and interpeak latencies I-V (IPL(I-V)) of the ABR was observed. No significant correlation (p=0.85) was found between hearing loss and interpeak latencies I-III (IPL(I-III)). These findings can be interpreted as indicating a marked delay in maturation of higher brainstem structures due to reduced auditory input during infancy. The correlation differs notably from results of comparable studies of adults published in recent literature. This leads to the assumption that the developing human brain is particularly sensitive to auditory deprivation. Thus, our results indicate the importance of a normal acoustic environment during sensitive periods in early childhood to ensure normal hearing and speech development.

Electrocochleography in children with auditory synaptopathy/neuropathy: Diagnostic findings and characteristic parameters

INTRODUCTION The early diagnosis of AS/AN in children remains challenging because it exclusively relies on the detection of OAE and/or CM, while ABR are pathologically changed or missing. The aim of our study was to ensure the diagnosis of AS/AN, demarcate it to an outer hair cell damage and possibly differentiate between pre- and postsynaptic pathologies. METHODS We retrospectively evaluated the transtympanic ECochG results of ten children with AS/AN and compared them to a matched group with SNHL and without any signs of AS/AN. We analyzed the thresholds, latencies and - as a new parameter - the amplitude ratio between CAP and SP. RESULTS CM and SP thresholds were significantly lower than CAP thresholds in AS/AN patients and significantly lower than SP and CM thresholds in SNHL patients with comparable CAP thresholds. The CAP/SP ratio of amplitudes in SNHL children was more than three times (significantly) higher than in AS/AN children. The cutoff value was set at 1.0 in order to differentiate between both groups with a 80-90% sensitivity and specificity. It was not possible to differentiate between a pre- and postsynaptic type of AS/AN in our collective. SUMMARY AND CONCLUSION The ECochG can add valuable information for a precise differential diagnosis of AS/AN, especially in babyhood. We identified the CAP/SP ratio as a new parameter for differentiation between AS/AN and SNHL. When the CAP/SP ratio falls below 1.0, patients can be diagnosed AS/AN with high specificity and sensitivity. Significantly smaller SPL are needed to evoke SP and CM in the AS/AN group, thus showing the preserved hair cell function.

A Method for the Induction of a Cochlea-Specific Auditory Deprivation in the Gerbil (Meriones unguiculatus)

The neurophysiological effects of early electrical stimulation on the development and neural plasticity of the central auditory system in prelingually deafened children with cochlear implants are still unknown. Many of these basic questions can be answered systematically only in animal experiments. Meriones unguiculatus is a well-established animal model in hearing research. Deafening is produced by a single intracochlear application of an ototoxic aminoglycoside antibiotic (neomycin sulfate) on the 14th day after birth (DAB), i.e. before the late natural onset of hearing on the 16th DAB. A single application of the antibiotic abolishes auditory brainstem responses (ABR) to clicks completely and reduces sensitivity to low frequency tonebursts by 50 dB SPL. Scanning electron microscopy results show a destruction of the stereocilia of the inner and outer hair cells of the basal and medial cochlear turn and a reduction of those in the apical turn. Our method avoids a systemic application of antibiotics and can be used in studies dealing with the consequences of different forms of auditory deprivation, neuronal compensation processes or with ontogenetic studies and chronic electrostimulation in an animal model.

Elektrophysiologische und psychoakustische Untersuchungen zur binauralen Signalverarbeitung normalhörender Erwachsener

ZusammenfassungHintergrund und Fragestellung. Zur Untersuchung binauraler Hörleistungen, die u. a. das Richtungshören beinhalten, gibt es bislang wenig validierte, klinisch einsetzbare Verfahren.Eine anwendbare elektrophysiologische Methode ist die Erfassung der sog. binauralen Differenzpotenziale (BDP) auf Hirnstammebene. Patienten/Methodik. Das BDP ist definiert als die Differenz zwischen der Reizantwort bei binauraler Stimulation und der Summe der Reizantworten bei jeweils monauraler Reizdarbietung.Im Rahmen einer konventionellen Ableitung der frühen akustisch evozierten Potenziale (FAEP) wurde die Registrierbarkeit und Langzeitstabilität des BDP an einem Kollektiv von 24 normalhörenden Erwachsenen untersucht. Darüber hinaus wurde der Einfluss der interauralen Laufzeitdifferenz (“interaural time difference”, ITD) auf die Latenzen und Amplituden der BDP erfasst.Zusätzlich wurden psychoakustische Untersuchungen zum Richtungshören in der Medianebene mit einem adaptiven Verfahren durchgeführt. Ergebnisse. Bei fast allen Probanden waren sämtliche Komplexe des binauralen Differenzpotenzials erfassbar und zeigten eine gute Test-Retest-Stabilität.Die zeitlichen Verzögerungen, die subjektiv den Eindruck einer Lateralisierung des Signals vermitteln,hatten einen deutlichen Einfluss auf die Interpeaklatenzen und Amplituden des BDP. Schlussfolgerungen. Binaurale Differenzpotenziale, die zumindest bei normalhörenden Versuchspersonen sicher und stabil registriert werden können, zeigen gewisse Zusammenhänge zu psychoakustischen Messungen der Lateralisierung und können der objektiven Erfassung binauraler Hörleistungen dienen.AbstractBackground and objective. At present, only a small number of validated, clinically usable methods for the assessment of binaural hearing capabilities exist.A proposed electrophysiological measure is the registration of the brainstem-based binaural difference potenzials (BDP). Patients/methods. The BDP is calculated as the difference between the binaurally evoked registration and the sum of the two monaural registrations.Detection and stability of the BDP were examined in 24 normally hearing adults within the framework of conventional registration of auditory brainstem responses. Furthermore, the influence of interaural time differences (ITD) on the BDP was determined. In addition, lateralization of the subjects was assessed using a psychoacoustical method. Results. The components of the BDP could be detected in almost all of the subjects. Moreover, they showed sufficient test-retestreliability. The impact of ITD,which causes lateralization of the stimulus,was clearly detectable for the latencies and the amplitudes of the BDP. Conclusions. Binaural difference potenzials, which are easily and reliably detectable reveal a relationship to the outcome of psychoacoustical assessment of lateralization and have the potenzial to provide a measure for binaural hearing capacity.

Case report of a child with otoacoustic emissions and profound hearing loss in whom otoacoustic emissions were preserved after cochlear implantation

Abstract The management of patients characterised by the presence of otoacoustic emissions and/or cochlear microphonics suggesting normal outer hair cell function in conjunction with absent or grossly abnormal auditory brainstem responses is often associated with particularly poor response to amplification. Cochlear implantation has been shown to be an option in affected patients. Here, we report a case of successful cochlear implantation and preserved otoacoustic emissions in a child suffering from this hearing disorder. Copyright

The correlation between ECochG parameters and early auditory behavior after cochlear implantation in children

Abstract Objective: The individual outcome after cochlear implantation in children with auditory synaptopathy/neuropathy (AS/AN) is difficult to predict. A tool for preoperative assessment would be helpful for counseling parents. This study evaluates the outcome after CI in children with AS/AN and with sensorineural hearing loss (SNHL), and correlates it with the preoperative ECochG results in order to find specific parameters of prognostic value. Design: The improvement of auditory behavior after CI was retrospectively assessed using the LittlEARS questionnaire and quantified in a score (LS). This score was correlated with the CAP/SP ratio in the preoperative ECochG. The score was further correlated with the patient’s age six months following CI. Study sample: Nine children with AS/AN were compared to nine children with SNHL. Results: Both groups showed a significant improvement in LS following CI. There was a significant positive correlation between the CAP/SP ratio and the improvement in LS in all children. The correlation between age and LS was significantly negative in the SNHL group and positive in the AS/AN group. Conclusion: All children with AS/AN and SNHL benefit to a similar extent from CI. The preoperatively assessed CAP/SP ratio has a prognostic value for the development of auditory behavior following CI.

[Auditory synaptopathy/neuropathy: clinical findings and diagnosis].

ZusammenfassungDie auditorische Synaptopathie/Neuropathie (AS/AN) stellt eine in ihrer Häufigkeit unterschätzte Form der sensorineuralen Schwerhörigkeit mit sehr heterogener klinischer Ausprägung dar. Bei vielen Betroffenen besteht die Hörstörung seit Geburt, bei einigen erst im Erwachsenenalter. Symptome sind der schwankende, meist beidseitig auftretende Hörverlust und die oft starke Einschränkung des Sprachverstehens, insbesondere im Störgeräusch. Otoakustische Emissionen (OAE) und cochleäre Mikrofonpotenziale (CM) lassen sich nachweisen, Stapediusreflexe fehlen und frühe akustisch evozierte Potenziale (FAEP) sind nicht nachweisbar oder stark verändert. Durch ein rein OAE-basiertes Neugeborenen-Hörscreening werden Kinder mit AS/AN nicht erkannt. Klinische Befunde, transtympanale Elektrocochleographie (ECochG) und weiterführende Diagnostik lassen die individuelle Ausprägung der AS/AN erkennen. Im Einzelfall können der Einsatz von Hörgeräten und/oder FM-Anlagen die Hör- und Kommunikationsfähigkeit verbessern. Sind diese Maßnahmen in Verbindung mit einer intensiven Hör-, Sprech- und Sprachfrühförderung unzureichend, stellen die CI-Versorgung oder der Einsatz alternativer Kommunikationsformen sinnvolle Optionen dar.AbstractAuditory synaptopathy/neuropathy (AS/AN) is a special subtype of sensorineural hearing disorders with heterogenous phenotypes and underestimated incidence. AS/AN generally develops in infancy, occasionally in adulthood. Symptoms include fluctuating, mostly bilateral hearing loss and abnormally reduced speech comprehension, especially in noisy environments. Within audiological assessments, patients with AS/AN present otoacoustic emissions (TEOAE; DPOAE) and cochlear microphonics (CM), absence of stapedius reflexes (SR) as well as absent or pathologically altered auditory evoked brainstem potentials (ABR). Children with AS/AN cannot be identified within OAE-based newborn hearing screening programs. Clinical findings, transtympanic electrocochleography (ECoG) and further diagnostic tools permit further identification of individual characteristics. In individual cases conventional amplification and the use of FM systems may improve hearing and communication skills. If these interventions, accompanied by intensive hearing, speech and language therapy are unsuccessful, cochlear implants (CI) or alternative forms of communication may be useful options for rehabilitation.Auditory synaptopathy/neuropathy (AS/AN) is a special subtype of sensorineural hearing disorders with heterogeneous phenotypes and underestimated incidence. AS/AN generally develops in infancy, occasionally in adulthood. Symptoms include fluctuating, mostly bilateral hearing loss and abnormally reduced speech comprehension, especially in noisy environments. Within audiological assessments, patients with AS/AN present otoacoustic emissions (TEOAE; DPOAE) and cochlear microphonics (CM), absence of stapedius reflexes (SR) as well as absent or pathologically altered auditory evoked brainstem potentials (ABR). Children with AS/AN cannot be identified within OAE-based newborn hearing screening programs. Clinical findings, transtympanic electrocochleography (ECoG) and further diagnostic tools permit further identification of individual characteristics. In individual cases conventional amplification and the use of FM systems may improve hearing and communication skills. If these interventions, accompanied by intensive hearing, speech and language therapy are unsuccessful, cochlear implants (CI) or alternative forms of communication may be useful options for rehabilitation.

Diagnostik und Therapie der auditorischen Synaptopathie/Neuropathie@@@Diagnosis and therapy of auditory synaptopathy/neuropathy

ZusammenfassungDie audiologische Konstellation von pathologischen frühen akustisch evozierten Potenzialen (fehlend, erhöhte Schwelle und gestörte Kurvenform) trotz nachweisbarer otoakustischer Emissionen geht häufig mit einer von schlechtem Sprachverständnis geprägten Schwerhörigkeit bzw. mit Taubheit einher. Diese als auditorische Neuropathie erstbeschriebene, heterogene Erkrankungsgruppe beinhaltet peripher-auditorische Störungen der synaptischen Schallkodierung durch innere Haarzellen (Synaptopathie) und/oder der Erregungsbildung und -weiterleitung im Hörnerv (Neuropathie). Dieses Konsensuspapier gibt aktuelle Hintergrundinformationen sowie Empfehlungen zur Diagnostik und Therapie im deutschsprachigen Raum. Es nimmt dabei Bezug auf aktuelle internationale Statements.AbstractPathological auditory brainstem responses (lack of responses, elevated thresholds and perturbed waveforms) in combination with present otoacoustic emissions are typical audiometric findings in patients with a hearing impairment that particularly affects speech comprehension or complete deafness. This heterogenous group of disorders first described as “auditory neuropathy” includes dysfunction of peripheral synaptic coding of sound by inner hair cells (synaptopathy) and/or of the generation and propagation of action potentials in the auditory nerve (neuropathy). This joint statement provides prevailing background information as well as recommendations on diagnosis and treatment. The statement focuses on the handling in the german language area but also refers to current international statements.