Auditory dysfunction in patients with cerebrovascular disease.

Auditory dysfunction is a common clinical symptom that can induce profound effects on the quality of life of those affected. Cerebrovascular disease (CVD) is the most prevalent neurological disorder today, but it has generally been considered a rare cause of auditory dysfunction. However, a substantial proportion of patients with stroke might have auditory dysfunction that has been underestimated due to difficulties with evaluation. The present study reviews relationships between auditory dysfunction and types of CVD including cerebral infarction, intracerebral hemorrhage, subarachnoid hemorrhage, cerebrovascular malformation, moyamoya disease, and superficial siderosis. Recent advances in the etiology, anatomy, and strategies to diagnose and treat these conditions are described. The numbers of patients with CVD accompanied by auditory dysfunction will increase as the population ages. Cerebrovascular diseases often include the auditory system, resulting in various types of auditory dysfunctions, such as unilateral or bilateral deafness, cortical deafness, pure word deafness, auditory agnosia, and auditory hallucinations, some of which are subtle and can only be detected by precise psychoacoustic and electrophysiological testing. The contribution of CVD to auditory dysfunction needs to be understood because CVD can be fatal if overlooked.

Environmental acoustic enrichment promotes recovery from developmentally degraded auditory cortical processing.

It has previously been shown that environmental enrichment can enhance structural plasticity in the brain and thereby improve cognitive and behavioral function. In this study, we reared developmentally noise-exposed rats in an acoustic-enriched environment for ∼4 weeks to investigate whether or not enrichment could restore developmentally degraded behavioral and neuronal processing of sound frequency. We found that noise-exposed rats had significantly elevated sound frequency discrimination thresholds compared with age-matched naive rats. Environmental acoustic enrichment nearly restored to normal the behavioral deficit resulting from early disrupted acoustic inputs. Signs of both degraded frequency selectivity of neurons as measured by the bandwidth of frequency tuning curves and decreased long-term potentiation of field potentials recorded in the primary auditory cortex of these noise-exposed rats also were reversed partially. The observed behavioral and physiological effects induced by enrichment were accompanied by recovery of cortical expressions of certain NMDA and GABAA receptor subunits and brain-derived neurotrophic factor. These studies in a rodent model show that environmental acoustic enrichment promotes recovery from early noise-induced auditory cortical dysfunction and indicate a therapeutic potential of this noninvasive approach for normalizing neurological function from pathologies that cause hearing and associated language impairments in older children and adults.

Partly reversible central auditory dysfunction induced by cerebral vasospasm after subarachnoid hemorrhage.

The authors describe a rare case of central auditory dysfunction induced by cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). A 55-year-old woman who was admitted after aneurysmal SAH developed cerebral vasospasm on Day 3 affecting mainly the right middle cerebral artery (MCA) and partly the left MCA. The vasospasm became refractory to conventional therapy and was ultimately improved by intraarterial infusion of nimodipine in the right MCA and angioplasty. Severe auditory dysfunction was apparent from Day 10 as the patient was not reactive to speech or environmental sounds. Brain MRI on Day 17 demonstrated infarcted areas mainly in the right hippocampus, medial occipital lobe, and thalamus. The patient underwent further examination using audiometry, speech testing, auditory evoked potentials, functional MRI, and cerebral PET. The initial diagnosis was extended nonverbal agnosia and total pure word deafness. The central auditory dysfunction improved over 6 months, with persisting hyperacusis, tinnitus, and amusia. Central auditory dysfunction is a rare complication after SAH. While cortical deafness may be associated with bilateral lesions of the temporal cortex, partly reversible central auditory dysfunction was observed in this patient after prominently unilateral right temporal lesions. The role of the interthalamic connections can be discussed, as well as the possibility that a less severe vasospasm on the left MCA could have transiently impaired the left thalamocortical auditory pathways.

Audiologic management of auditory neuropathy spectrum disorder in children: a systematic review of the literature.

PURPOSE: This review summarizes current evidence related to the audiologic management of children with auditory neuropathy spectrum disorder (ANSD). METHOD: A systematic search of the literature was conducted in 25 electronic databases (e.g., PubMed, CINAHL, and ERIC) using key words such as auditory neuropathy, auditory neuropathy spectrum disorder, auditory neuropathy/dyssynchrony, and hearing loss. Eighteen studies met the inclusion criteria by addressing 1 or more of 8 clinical questions. Studies were evaluated for methodological quality, and data regarding participant, intervention, and outcome variables are reported. RESULTS: Fifteen of the 18 studies addressed the use of cochlear implantation, and 4 addressed conventional acoustic amplification. All participants demonstrated improved auditory performance; however, all 18 studies were considered exploratory, and many had methodological limitations. CONCLUSION: The clinical evidence related to intervention for ANSD is at a very preliminary stage. Additional research is needed to address the efficacy of acoustic amplification and cochlear implantation in children with ANSD and the impact of this disorder on developmental outcomes.

Multi-site diagnosis and management of 260 patients with auditory neuropathy/dys-synchrony (auditory neuropathy spectrum disorder).

Test results and management data are summarized for 260 patients with diagnoses of Auditory Neuropathy Spectrum Disorder (ANSD). Hearing aids were tried in 85 of these patients, and 49 patients tried cochlear implants. Approximately 15% reported some benefit from hearing aids for language learning, while improvement in speech comprehension and language acquisition was reported in 85% of patients who were implanted. Approximately 5% (13/260) of the total population developed normal speech and language without intervention. Patients were diagnosed at our laboratory (n=66) or referred from other sites (n=194), and all showed absent/grossly abnormal auditory brainstem responses (ABR), often 'ringing' cochlear microphonics, and the presence or history of otoacoustic emissions. Etiologies and co-existing conditions included genetic (n=41), peripheral neuropathies (n=20), perinatal jaundice and/or anoxia and/or prematurity (n=74). These patients comprise 10% or more of hearing impaired patients; their language acquisition trajectories are generally unpredictable from their audiograms.

Cochlear implantation in children with auditory neuropathy spectrum disorder.

OBJECTIVE: To report the patient's characteristics, preoperative audiological profiles, surgical outcomes, and postoperative performance for children with auditory neuropathy spectrum disorder (ANSD) who ultimately received cochlear implants (CIs). DESIGN: Prospective, longitudinal study of children with ANSD who received CIs after a stepwise management protocol that included electrophysiologic and medical assessment, documentation of behavioral audiometric thresholds and subsequent fitting of amplification according to Desired Sensation Level targets, auditory-based intervention with careful monitoring of skills development and communication milestones, and finally implantation when progress with the use of acoustic amplification was insufficient. RESULTS: Of 140 children with ANSD, 52 (37%) received CIs in their affected ears (mean duration of use of 41 mos). Many of these children were born prematurely (42%) and impacted by a variety of medical comorbidities. More than one third (38%) had abnormal findings on preoperative magnetic resonance imaging of the brain and inner ear, and 81% had a greater than severe (>70 dB HL) degree of hearing loss before implantation. Although 50% of the implanted children with ANSD demonstrated open-set speech perception abilities after implantation, nearly 30% of them with >6 months of implant experience were unable to participate in this type of testing because of their young age or developmental delays. No child with cochlear nerve deficiency (CND) in their implanted ear achieved open-set speech perception abilities. In a subgroup of children, good open-set speech perception skills were associated with robust responses elicited on electrical-evoked intracochlear compound action potential testing when this assessment was possible. CONCLUSIONS: This report shows that children with ANSD who receive CIs are a heterogeneous group with a wide variety of impairments. Although many of these children may ultimately benefit from implantation, some will not, presumably because of a lack of electrical-induced neural synchronization, the detrimental effects of their other associated conditions, or a combination of factors. When preoperative magnetic resonance imaging reveals central nervous system pathology, this portends a poor prognosis for the development of open-set speech perception, particularly when CND is evident. These results also show that electrical-evoked intracochlear compound action potential testing may help identify those children who will develop good open-set speech perception. Instead of recommending CI for all children with electrophysiologic evidence of ANSD, the stepwise management procedure described herein allows for the identification of children who may benefit from amplification, those who are appropriate candidates for cochlear implantation, and those who, because of bilateral CND, may not be appropriate candidates for either intervention.

Avaliação de crianças com distúrbio do processamento auditivo antes e após terapia fonoaudiológica / Evaluation of children with auditory processing disorder before and after speech therapy

A influência terapêutica no processamento auditivo pode mudar as habilidades de audição, mostrando a capacidade do sistema nervoso auditivo de ajudar no desenvolvimento da fala, principalmente no aspecto de linguagem. O presente trabalho teve como objetivo avaliar o Distúrbio do Processamento Auditivo Central e a Consciência Fonológica de duas crianças sem perda auditiva, para refletir sobre o processo terapêutico nesses distúrbios. O estudo foi realizado com crianças do sexo masculino, oito e nove anos, que tem limiares auditivos dentro dos padrões de normalidade,porém apresentaram Distúrbio do Processamento Auditivo central. Após o diagnóstico, realizado por meio de exames de Processamento Auditivo e de Consciência Fonológica,as crianças foram submetidas à intervenção fonoaudiológicaindividual, com abordagem formal e informal, duas vezes por semana durante 40 minutos cada, totalizando 18 sessões. Na sequencia, os mesmos exames foram reaplicados, visando comparar as etapas pré e pós-intervenção. O resultado do participante A mostrou uma melhoria nas habilidades auditivas, encontrando-se na reavaliação redução de déficits e melhora das respostas no Protocolo de Consciência Fonológica. O participante B apresentou melhora quantitativa no processamento auditivo, no entanto, manteve os mesmos déficits e as mesmas respostas no protocolo. Os resultados apontam para a possibilidade de uma estreita relação das habilidades auditivas com o desenvolvimento cognitivo e metalingüístico, e destaca a necessidade de garantir um trabalho integrado entre fonoaudiólogos, pais e professores, com o objetivo de proporcionar melhores condições para o aprendizado.

Therapeutic influence on auditory processing can change hearing skills, showing the capacity the auditory nervous system has to change and to help on the development of speech, mainly in the language aspect. The present work aimed at evaluating and watching the Central Auditory Processing Disorder and Phonological Awareness of two children with hearing skills loss to prove the importance of therapeutic process to people who have these desorders. The study was performed with two male kids of 8 and 9 years old, with normal hearing threshold, however presenting Auditory Processing Disorder. After the diagnosis, the kids received individual speech therapy with formal and informal approach, twice a week for 40 minutes each, with a total of 18 sessions. At the end of the sessions, new exams were performed and the protocol of Phonological Awareness was used to quantify the previous and post results. The results from patient "A" show a significant improvement in hearing skills. there were a two point loss for one point gain in the reevaluation and the responses in the phonological awareness protocol were better. Patient "B" showed quantitative improvement in the auditory processing; however, he kept the loss and the same responses in the protocol. Therefore, the findings show the importance of evaluation of Auditory Processing and Phonological Awareness before and after speech therapy, proving the progress of hearing skills that reveal a close relation with cognitive and metalinguistisc development, providing information for the improvement of speech, which will help the child to integrate socialy.

La influencia terapéutica sobre el procesamiento auditivo puede cambiar la actuación de la habilidad auditiva, demostrando la capacidad de modificación del Sistema Nervioso Auditivo Céntrico (SNAC) y favoreciendo el desarrollo de las funciones del lenguaje, principalmente en el aspecto fonológico. Este trabajo objetivó evaluar y monitorar el Disturbio del Procesamiento Auditivo Céntrico (DPAC) e Consciencia Fonológica de dos niños con déficit en las habilidades auditivas a fin de comprobar la importancia del proceso terapéutico para participante s portadores de tales disturbios. El estudio fue desarrollado con dos niños del sexo masculino de 8 (ocho) e 9 (nueve) años, que presentan umbrales auditivos dentro de los padrones de normalidad, sin embargo con DPAC. Ulteriormente al cierre del diagnóstico, los niños fueron sometidos a la intervención fonoaudilógica individual, utilizando el abordaje formal y informal, realizada en dos sesiones por semana con duración de 40 minutos cada, totalizando 18 (dieciocho) sesiones. Al término de estas, fueron hechas nuevamente los exámenes de Procesamiento Auditivo y aplicación del protocolo de Consciencia Fonológica, visando cuantificar los resultados pre y post-intervención. Los resultados obtenidos en el participante "A" ilustran una mejora significativa de las habilidades auditivas, encontrándose en la reevaluación reducción de dos déficits para solamente un y mejora de las respuestas en el Protocolo de Consciencia Fonológica. El participante "B" presentó mejora cuantitativa en las pruebas de Procesamiento Auditivo, sin embargo permaneciendo los mismo déficits y las mismas respuestas en el protocolo de Consciencia Fonológica. Luego, los hallazgos demuestran la importancia de la evaluación del Procesamiento Auditivo y de la Consciencia Fonológica antes y después de la intervención, comprobando el progreso de las habilidades auditivas que revelan una estrecha relación con el desarrollo maturicional, cognitivo y metalingüístico, suministrando subsidios para el perfeccionamiento del lenguaje, proporcionando mejor integración del niño en el medio social.

Neuropatía auditiva, diagnóstico y manejo audiológico / Auditory neuropathy / dyssychrony, assessment and audiologic management

Los hallazgos clínicos que definen una neuropatía/des sincronía (NA/DA) son la integridad de las células ciliadas evidenciado, mediante la presencia de emisiones otoacústicas evocadas (EOAe) y/o la presencia de potenciales microfónicos cocleares (PMIC), junto con la ausencia de actividad neural evocada a nivel del VIII par craneano (potencial de acción compuesto) y tronco cerebral (potencial evocado auditivo de tronco (PEAT)). Las condiciones clínicas relacionadas con una NA/DA incluyen a la hiperbilirrubinemia, enfermedades neurovegetativas (ejemplo ataxia de Friedreich), síndrome de Charcot-Marie-Tooth así como otras neuropatías sensoriomotoras, desórdenes mitocondriales y neuropatías isquémica-hipóxicas como resultados de asfixia. El desarrollo de las habilidades auditivas y comunicacionales pueden estar comprometidas en forma importante en los niños con aparición prelingual de una NA/DA, mayor es aún este compromiso al no existir un perfil pronóstico preestablecido del desarrollo y resultados en el tratamiento de este desorden. En la actualidad existen múltiples estudios en donde se ha observado que hasta 50 por ciento de los pacientes con NA/DA presentan algún grado de beneficio al usar audífonos por lo que se sugiere que sistemas de amplificación como los audífonos o incluso implante coclear deberían ser el primer paso en el proceso de (re)habilitación.

The clinical findings that define an auditory neuropathy/dyssynchrony (AN/Dys) are the integrity of the outer hair cells demonstrated by the presence of evoked otoacoustics emissions (OAEe) and/or the presence of cochlear microphonic potential (CMP) along with the absence of neural activity evoked at level of VIII nerve (action potential compound) and brainstem (Auditory Brainstem Response, ABR). The clinical conditions related to an AN they include hiperbilirrubinemia, neurodegenerative diseases (eg ataxia of Friedreich), Charcot-Marie-Tooth syndrome as well as other sensoriomotor neuropathies, mitocondrial disorders and hypoxic neuropathy as perinatal asphyxia. The development of the auditory and communicational abilities can be compromise in children with prelingual onset of an AN/Dys, the development and results of treatment of this disorder is still this commitment when not existing a profile prognosis. At the present time multiple studies have been observed that until a 50 percent of the patients with AN present some degree of benefit using hearing aids, reason why it suggests amplification systems as the hearing aids or even cochlear implant would have to be the first step in the process of (re) habilitation of these patients.

Speech and language outcomes in children with auditory neuropathy/dys-synchrony managed with either cochlear implants or hearing aids.

The aim of this study was to assess the receptive language and speech production abilities of a group of school-aged children with auditory neuropathy/dys-synchrony-type hearing loss. Ten children who had received a cochlear implant in one or both ears participated. Findings for this group were compared with those for a matched cohort of implanted children with other forms of sensorineural hearing loss and with those for a group of auditory neuropathy/dys-synchrony children who were long-term hearing aid users. Results for 9 of the ten implanted children with auditory neuropathy/dys-synchrony were similar to those of the general population of paediatric implant recipients. (One child, who gained little perceptual benefit from his device, showed severely delayed spoken language development). Results for the group of aided auditory neuropathy/dys-synchrony subjects were comparable to those for their implanted counterparts suggesting that affected children should not automatically be considered cochlear implant candidates.

Migraine associated with auditory-vestibular dysfunction.

UNLABELLED: The association between hearing and balance disorders with migraine is known since the times of the ancient Greeks, when Aretaeus from Cappadocia in 131 B.C, made an accurate and detailed description of this occurrence during a migraine episode. We present a broad review of migraine neurotological manifestations, using the most recent publications associated with epidemiology, clinical presentation, pathophysiology, diagnostic methods and treatment for this syndrome. AIM: To describe the clinical entity: "Migraine associated with auditory-vestibular dysfunction" in order to help otorhinolaryngologists and neurologists in the diagnosis and management of such disorder. FINAL REMARKS: There is a strong association between neurotological symptoms and migraine, and the auditory-vestibular dysfunction-associated migraine is the most common cause of spontaneous episodic vertigo (non-positional). Symptoms may vary broadly among patients, making it a diagnostic challenge to the otorhinolaryngologist. This entity usually presents with positional or spontaneous vertigo spells, lasting for seconds or days, associated with migraine symptoms. A better understanding of the relationship between central vestibular mechanisms and migraine mechanisms, besides the discovery of ionic channel disorders in some cases of migraine, ataxia and vertigo, may lead to a better understanding of migraine pathophysiology associated with audio-vestibular disorder.

Enxaqueca associada a disfunção auditivo-vestibular: [revisão] / Migraine associated with auditory-vestibular dysfunction: [review]

A associação de distúrbios da audição e equilíbrio com enxaqueca é reconhecida desde a Grécia antiga quando Aretaeus da Capadócia em 131 a.C., fez uma descrição precisa e com detalhes desta ocorrência durante uma crise de enxaqueca. Uma revisão ampla das manifestações otoneurológicas da enxaqueca é apresentada, usando as mais recentes publicações com respeito à epidemiologia, apresentação clínica, fisiopatologia, métodos diagnósticos e manejo desta síndrome. OBJETIVO: Descrever a entidade clínica "Enxaqueca associada a Disfunção Auditivo-vestibular" no intuito de ajudar médicos otorrinolaringologistas e neurologistas no diagnóstico e no manejo clínico dessa doença. COMENTÁRIOS FINAIS: Uma forte associação existe entre sintomas otoneurológicos e enxaqueca, sendo a enxaqueca associada a disfunção auditivo-vestibular a causa mais comum de vertigem episódica espontânea (não-posicional). Os sintomas podem variar bastante entre pacientes tornando um desafio diagnóstico para o otorrinolaringologista. Esta entidade geralmente se apresenta com ataques de vertigem espontâneos ou posicionais, durando de segundos a dias com sintomas de enxaqueca associados. Uma melhor elucidação da ligação entre os mecanismos vestibulares centrais e os mecanismos da enxaqueca em si, além da descoberta de defeitos em canais iônicos em algumas causas de enxaqueca, ataxia e vertigem, podem levar a um entendimento maior da fisiopatologia da enxaqueca associada a disfunção auditivo-vestibular.

The association between hearing and balance disorders with migraine is known since the times of the ancient Greeks, when Aretaeus from Cappadocia in 131 B.C, made an accurate and detailed description of this occurrence during a migraine episode. We present a broad review of migraine neurotological manifestations, using the most recent publications associated with epidemiology, clinical presentation, pathophysiology, diagnostic methods and treatment for this syndrome. AIM: to describe the clinical entity: "Migraine associated with auditory-vestibular dysfunction" in order to help otorhinolaryngologists and neurologists in the diagnosis and management of such disorder. FINAL REMARKS: There is a strong association between neurotological symptoms and migraine, and the auditory-vestibular dysfunction-associated migraine is the most common cause of spontaneous episodic vertigo (non-positional). Symptoms may vary broadly among patients, making it a diagnostic challenge to the otorhinolaryngologist. This entity usually presents with positional or spontaneous vertigo spells, lasting for seconds or days, associated with migraine symptoms. A better understanding of the relationship between central vestibular mechanisms and migraine mechanisms, besides the discovery of ionic channel disorders in some cases of migraine, ataxia and vertigo, may lead to a better understanding of migraine pathophysiology associated with audio-vestibular disorder.

Inferior colliculus responses to multichannel microstimulation of the ventral cochlear nucleus: implications for auditory brain stem implants.

Multichannel techniques were used to assess the frequency specificity of activation in the central nucleus of the inferior colliculus (CIC) produced by electrical stimulation of localized regions within the ventral cochlear nucleus (VCN). Data were recorded in response to pure tones from 141 and 193 multiunit clusters in the rat VCN and the CIC, respectively. Of 141 VCN sites, 126 were individually stimulated while recording responses in the CIC. A variety of CIC response types were seen with an increase in both electrical and acoustic stimulation levels. The majority of sites exhibited monotonic rate-level types acoustically, whereas spike rate saturation was achieved predominantly with electrical stimulation. In 20.6% of the 364 characteristic frequency aligned VCN-CIC pairs, the CIC sites did not respond to stimulation. In 26% of the 193 CIC sites, a high correlation was observed between acoustic tuning and electrical tuning obtained through VCN stimulation. A high degree of frequency specificity was found in 58% of the 118 lowest threshold VCN-CIC pairs. This was dependent on electrode placement within the VCN because a higher degree of frequency specificity was achieved with stimulation of medial, central, and posterolateral VCN regions than more anterolateral regions. Broadness of acoustic tuning in the CIC played a role in frequency-specific activation. Narrowly tuned CIC sites showed the lowest degree of frequency specificity on stimulation of the anterolateral VCN regions. These data provide significant implications for auditory brain stem implant electrode placement, current localization, power requirements, and facilitation of information transfer to higher brain centers.

Transcranial magnetic stimulation for the treatment of tinnitus: a new coil positioning method and first results.

Auditory phantom perceptions are associated with hyperactivity of the central auditory system. Neuronavigation guided repetitive transcranial magnetic stimulation (rTMS) of the area of increased activity was demonstrated to reduce tinnitus perception. The study aimed at developing an easy applicable standard procedure for transcranial magnetic stimulation of the primary auditory cortex and to investigate this coil positioning strategy for the treatment of chronic tinnitus in clinical practice. The left gyrus of Heschl was targeted in 25 healthy subjects using a frameless stereotactical system. Based on individual scalp coordinates of the coil, a positioning strategy with reference to the 10--20-EEG system was developed. Using this coil positioning approach we started an open treatment trial. 28 patients with chronic tinnitus received 10 sessions of rTMS (intensity 110% of motor threshold, 1 Hz, 2000 Stimuli/day). Being within a range of about 20 mm diameter, the scalp coordinates for stimulating the primary auditory cortex allowed to determine a standard procedure for coil positioning. Clinical validation of this coil positioning method resulted in a significant improvement of tinnitus complaints (p<0.001). The newly developed coil positioning strategy may have the potential to offer a more easy-to-use stimulation approach for treating chronic tinnitus as compared with highly sophisticated, imaging guided treatment methods.

Avaliação da função auditiva central em idosos e suas contribuições para a adaptação de próteses auditivas / Central auditory function assessment and its contributions for hearing aids fitting

O presente estudo investigou a função auditiva central em idosos que, submetidos ao processo de seleção e adaptação de prótese auditiva, não obtiveram sucesso com a adaptação binaural, relatando melhor aproveitamento com o uso da amplificação monoaural, mesmo apresentando perda auditiva bilateral simétrica. Após a aplicação de um questionário para a investigação dos possíveis fatores que poderiam ter contribuído para a rejeiçao da prótese auditiva, os sujeitos foram submetidos à avaliação da função auditiva periférica, composta por audiometria tonal, vocal e medidas de imitância acústica e à avaliação da função auditiva central, por meio dos testes Dígitos Dicóticos e Dissílabos Alternados e Sobrepostos. Realizou-se uma análise qualitativa buscando relacionar os resultados de aplicação dos testes da função auditiva central e a preferência do sujeito quanto à amplificação e compreender se uma possível discrepância entre a performance nas duas orelhas constituiria um fator que contribuiu para a opção de adaptação monoaural. Apenas um sujeito apresentou resultados discrepantes entre as duas orelhas, e a orelha que obteve resultados melhores apresentava maior aproveitamento com a amplificação. Concluiu-se que a presença de um comprometimento da função auditiva central pode interferir negativamente no processo de seleção e adaptação de próteses auditivas. Portanto, mostra-se necessária a inclusão de testes que avaliam essa função no processo de seleção e adaptação de próteses auditivas, especialmente nos casos de pacientes idosos.

Auditory neuropathy: a potentially under-recognized neonatal intensive care unit sequela.

Auditory neuropathy (AN) is a hearing disorder that affects newborns. Those with high-risk neonatal histories, family history of childhood hearing loss, and hyperbilirubinemia are at greatest risk. Current neonatal intensive care unit (NICU) hearing screening methods that rely only on otoacoustic emissions will fail to detect this disorder. Auditory neuropathy differs from conductive hearing loss and sensorineural hearing loss; a specific constellation of findings on audiologic evaluation are diagnostic of this disorder. The pathophysiology of AN is unclear; however, it may be caused by demyelinization or degeneration at points along the auditory pathway. The actual incidence of AN is unknown; it is more prevalent in high-risk infants. The course of AN varies widely among patients. Current management ranges from close monitoring of the child's development to cochlear implantation. Neonatal intensive care unit nurses need to be aware of this disorder to help support and educate at-risk families and to alert them of the need to monitor hearing and language development in their infants.

Auditory neuropathy/dyssynchrony: its diagnosis and management.

Patients with auditory neuropathy/dyssynchrony exhibit no auditory brain stem response (ABR), no middle ear muscle response, and both normal otoacoustic emissions or normal cochlear microphonics. An absent or grossly abnormal ABR is not always associated with deafness. In contrast, a hearing loss of 30 dB or more usually predicts absent otoacoustic emissions, but normal emissions can be seen in some patients whose behavioral audiograms imply total deafness. This article reviews the underlying physiology that makes these tests both useful and potentially misleading, and recommends steps to be considered by primary care physicians and other professionals to compensate for the vulnerabilities of each of the procedures.

Aetiology and clinical presentations of auditory processing disorders--a review.

Auditory processing disorders may have detrimental consequences on a child's life, if undiagnosed and untreated. We review causes of auditory processing disorders in order to raise clinical awareness. Auditory processing disorders may present against a background of neurological disease or developmental disorders, as well as in isolation. Clinicians need to be aware of potential causes and implications of auditory processing disorders.

Regeneration and recovery of the hearing function of the central auditory pathway by transplants of embryonic brain tissue in adult rats.

The present study is the first report of successful regeneration and recovery of hearing function of the central auditory pathway after transection in the adult rat. The ventral cochlear tract in the brain stem to pons was transected on one side in adult rats. Tissue from embryos (E14 to E16) was used to cover the lesion site. In 30% of the rats examined, the axons regrew beyond the transected site and regenerated into the denervated side and terminated at the normal targets. The hearing function of rats was elucidated by recording the auditory brain stem response (ABR). Rats with successful regeneration showed nearly normal ABR. In rats receiving simple transection without covering embryonic tissue, there was no regeneration and hearing function did not recover. Thus, the present findings contradict the widely held view that the adult mammalian central auditory system cannot be restored following damage.