Systematic review protocol for assessing central auditory functions of Alzheimer's disease and its preclinical stages.

INTRODUCTION: A number of studies have reported an association between peripheral hearing impairment, central auditory processing and Alzheimer's disease (AD) and its preclinical stages. Both peripheral hearing impairment and central auditory processing disorders are observed many years prior to the clinical manifestation of AD symptoms, hence, providing a long window of opportunity to investigate potential interventions against neurodegenerative processes. This paper outlines the protocol for a systematic review of studies examining the central auditory processing functions in AD and its preclinical stages, investigated through behavioural (clinical assessments that require active participation) central auditory processing tests. METHODS AND ANALYSIS: We will use the keywords and Medical Subject Heading terms to search the following electronic databases: MEDLINE, PsychINFO, PubMed, Scopus, EMBASE and CINAHL Plus. Studies including assessments of central auditory function in adults diagnosed with dementia, AD and its preclinical stages that were published before 8 May 2019 will be reviewed. This review protocol will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols guidelines. Data analysis and search results will be reported in the full review. This manuscript has designed the protocols for a systematic review that will identify the behavioural clinical central auditory processing measures that are sensitive to the changes in auditory function in adults with AD and its preclinical stages. Such assessments may subsequently help to design studies to examine the potential impact of hearing and communication rehabilitation of individuals at risk of AD. ETHICS AND DISSEMINATION: Ethical approval is not required as this manuscript only reports the protocols for conducting a systematic review as primary data will only be reviewed and not be collected. The results of this systematic review will be disseminated through publication and in scientific conferences. PROSPERO REGISTRATION NUMBER: CRD42017078272.

Central auditory processing disorders after mild traumatic brain injury.

Auditory processing disorders are common following mild traumatic brain injury (mTBI), but the neurocircuitry involved is not well understood. The present study used functional MRI to examine auditory cortex activation patterns during a passive listening task in a normative population and mTBI patients with and without clinical central auditory processing deficits (APD) as defined by the SCAN-3:A clinical battery. Patients with mTBI had overall patterns of lower auditory cortex activation during the listening tasks as compared to normative controls. A significant lateralization pattern (pairwise t-test; p⟨0.05) was observed in normative controls and in those with mTBI and APD during single-side stimulation. Additionally, baseline connectivity between left and right auditory cortices was lower in mTBI patients than in controls (p=0.01) and significantly reduced in the mTBI with APD group (p=0.008). Correlation was also observed between bilateral task-related activation and competing words subscore of the SCAN-3:A. These findings suggest the passive listening task is well suited to probe auditory function in military personnel with an mTBI diagnosis. Further, the study supports the use of multiple approaches for detecting and assessing central auditory deficits to improve monitoring of short- and long-term outcomes.

Diagnóstico del desorden del procesamiento auditivo central / Diagnosis of central auditory processing disorder

CONTEXTO CLÍNICO: Una alteración en el lenguaje se refiere a un impedimento en la capacidad de recibir, enviar, processar y comprender conceptos o sistemas de símbolos verbales, no verbales y gráficos. El desarrollo normal de la comunicación requiere la interacción de un mecanismo intacto con un entorno favorable. Dentro de los componentes responsables de este mecanismo se incluyen la sensibilidad auditiva, percepción, inteligencia, integridad estructural, habilidad motora y estabilidad emocional. Los desórdenes del procesamiento auditivo central (DPAC) se definen como un déficit en el procesamiento de la información relacionada en forma específica a la modalidad auditiva, este déficit puede verse exacerbado en ambientes en donde las condiciones acústicas son desfavorables. Estos déficits pueden estar asociados a dificultades auditivas, de comprensión del habla, desarrollo del lenguaje y aprendizaje. Un DPAC es resultado de una disfunción en el procesamiento de la información auditiva pudiendo o no coexistir con una disfunción global que afecte el desempeño a través de otras modalidades (por ejemplo: déficit de atención, déficit en la representación del lenguaje, entre otros). La prevalencia de este desorden varía levemente según diferentes investigadores, los datos más recientes señalan este rango entre 2% y 3% de los niños a una razón de 2:1 entre hombre y mujeres. TECNOLOGÍA: El profesional a cargo debe seleccionar la batería de pruebas adecuadas para el diagnóstico de DPAC. La selección de éstas debe basarse en los hallazgos de la historia del caso, la evaluación interdisciplinaria (por ejemplo, los resultados del lenguaje y las evaluaciones cognitivas) y la evaluación audiológica periférica. La batería de pruebas se puede usar para diagnosticar una alteración en uno o más processos neurofisiológicos que ocurren cuando las señales auditivas viajan a través del SNAC. La identificación de déficits específicos en los SNAC puede llevar a recomendaciones específicas y planes de tratamiento. OBJETIVO: El objetivo del presente informe es evaluar la evidencia disponible acerca de la capacidad diagnóstica y los aspectos relacionados a las políticas de cobertura del uso de las pruebas diagnósticas en el desorden del procesamiento auditivo central. MÉTODOS: Se realizó una búsqueda en las principales bases de datos bibliográficas, en buscadores genéricos de internet, y financiadores de salud. Se priorizó la inclusión de revisiones sistemáticas (RS), ensayos clínicos controlados aleatorizados (ECAs), evaluaciones de tecnologías sanitarias (ETS), evaluaciones económicas, guías de práctica clínica (GPC) y políticas de cobertura de diferentes sistemas de salud. RESULTADOS: Se incluyeron una RS, siete GPC y siete informes de políticas de cobertura sobre pruebas diagnósticas para el desorden del procesamiento auditivo central. CONCLUSIONES: Evidencia de baja calidad sugiere que las pruebas diagnósticas utilizadas actualmente en el desorden del procesamiento auditivo central (DPAC) podrían ser de utilidad para su abordaje diagnóstico. No se hallaron estudios que evalúen la precisión diagnóstica de un conjunto de pruebas en pacientes con sospecha de DPAC. Las guías de práctica clínica (GPC) relevadas expresan que no existe un patrón de oro para realizar el diagnóstico de DPAC, por lo tanto, la selección de las distintas pruebas debería ajustarse a las características y condiciones del paciente. Las mismas GPC recomiendan el uso de una batería de pruebas (de comportamiento o electrofisiológicas) para el abordaje diagnóstico del DPAC, debido a que en su conjunto mejorarían la precisión diagnóstica. Una GPC intersociedades de Europa recomienda una batería determinada de pruebas para iniciar el abordaje diagnóstico, constituído por la prueba de dígitos dicóticos, las de patrones de frecuencia y de duración, Gaps-In-Noise (GIN), prueba de habla en ruido, diferencia de umbrales binaurales enmascarados, y la prueba de inteligibilidad del habla pediátrica. Los financiadores públicos de salud que han sido relevados no contemplan la cobertura de las pruebas para el diagnóstico de DPAC. Dentro de los financiadores privados de salud de los Estados Unidos, dos no brindan cobertura ya que la consideran en fase experimental, mientras que otros dos otorgan cobertura para el abordaje diagnóstico del DPAC, y en esos casos, la batería de pruebas será seleccionada según criterio del profesional tratante.

[The application of the screening questionnaires for the diagnostics of the central auditory processing disorders in the pediatric practice]. / Ispol'zovanie skriningovykh anket dlia vyiavleniia tsentral'nykh slukhovykh rasstroistv v pediatricheskoi praktike.

Identification and diagnostics of auditory processing disorders (APD) in the children continues to be a challenge. Screening tools help to decide the need for evaluation. However, none of them are used routinely in Russia, nor are there thus far auditory checklist questionnaires in the Russian language. The aim of his study was to approve Children's Auditory Performance Scale (CHAPS) and Fisher's Auditory Checklist in Russian for the children at the age of 5-10 years. The study included 52 children at the age from 5 to 11 years. All of them were native Russian speakers. Pure tone audiometry, immitancemetry, and the Simplified RuMatrix test were performed for all the children. All of them had normal hearing thresholds, speech and language development, and normal academic achievement at school. The parents filled in the CHAPS and Fisher's Auditory Checklist questionnaires in Russian. The mean value of Fisher's Auditory Checklist was 85.7 ± 9.3, the mean value of CHAPS questionnaire was equal to 0.08 ± 0.26. The results obtained with the use of the Russian language questionnaires are in excellent agreement with the test data yielded by the respective English language versions. It is recommended that the clinical assessment for APD should be performed for children with the result of the Fisher questionnaire less than 67 points and with the result of the CHAPS questionnaire less than -1 point. It is concluded that Fisher's questionnaire was more convenient for the parents to fill in.

Auditory function in Pelizaeus-Merzbacher disease.

Pelizaeus-Merzbacher disease (PMD; MIM 312080), an inherited defect of central nervous system myelin formation, affects individuals in many ways, including their hearing and language abilities. The aim of this study was to assess the auditory abilities in 18 patients with PMD by examining the functional processes along the central auditory pathways using auditory brainstem responses (ABR) and cortical auditory evoked potentials (CAEP) in response to speech sounds. The significant ABR anomalies confirm the existence of dyssynchrony previously described at the level of the brainstem in patients with PMD. Despite the significant auditory dyssynchrony observed at the level of the brainstem, CAEPs were present in most patients, albeit somehow abnormal in terms of morphology and latency, resembling a type of auditory neuropathy spectrum disorder.

Auditory system dysfunction in Alzheimer disease and its prodromal states: A review.

Recent findings suggest that both peripheral and central auditory system dysfunction occur in the prodromal stages of Alzheimer Disease (AD), and therefore may represent early indicators of the disease. In addition, loss of auditory function itself leads to communication difficulties, social isolation and poor quality of life for both patients with AD and their caregivers. Developing a greater understanding of auditory dysfunction in early AD may shed light on the mechanisms of disease progression and carry diagnostic and therapeutic importance. Herein, we review the literature on hearing abilities in AD and its prodromal stages investigated through methods such as pure-tone audiometry, dichotic listening tasks, and evoked response potentials. We propose that screening for peripheral and central auditory dysfunction in at-risk populations is a low-cost and effective means to identify early AD pathology and provides an entry point for therapeutic interventions that enhance the quality of life of AD patients.

Adverse effects of pesticides on central auditory functions in tobacco growers.

OBJECTIVE: To investigate the effects of exposure to pesticides on the central auditory functions (CAF) of Brazilian tobacco growers. DESIGN: This was a cross-sectional study carried out between 2010 and 2012. Participants were evaluated with two behavioural procedures to investigate CAF, the random gap detection test (RGDT) and the dichotic digit test in Portuguese (DDT). STUDY SAMPLE: A total of 22 growers exposed to pesticides (study group) and 21 subjects who were not exposed to pesticides (control group) were selected. RESULTS: No significant differences between groups were observed for pure-tone thresholds. A significant association between pesticide exposure and the results for RGDT and DDT was found. Significant differences between pesticide-exposed and nonexposed subjects were found for RGDT frequency average and DDT binaural average, when including age and hearing level as covariates. Age was significantly associated with RGDT frequency average, DDT left ear score, DDT binaural average and DDT right ear advantage. Hearing levels were not significantly associated with any of the test scores. The relative risk of failing the DDT and RGDT for the study group was 1.88 (95% CI: 1.10-3.20) and 1.74 (95% CI: 1.06-2.86), respectively, as compared with the control group. CONCLUSIONS: The results showed that tobacco growers exposed to pesticides exhibited signs of central auditory dysfunction characterised by decrements in temporal processing and binaural integration processes/abilities.

Discrepancy between self-reported and interviewed psychosis risk symptoms: auditory distortions are the most reliably reported symptom by self-report.

AIM: In the recent literature, there has been growing interest in assessment methods for detecting increased risk of developing psychosis. Self-report methods are popular but may lead to different results compared to clinical interviews. METHODS: The difference in psychosis risk scores was tested between self-reported psychosis risk symptoms (PROD-SR) and self-reported symptoms additionally confirmed by interview (PROD-SR + I). The symptom categories were derived from 12 common psychosis risk symptoms included in the PROD screening instrument. The data were collected by questionnaires and interviews conducted with 395 adolescents (mean age 15.3 years) in an early intervention and detection team, JERI, at Helsinki University Central Hospital, Finland. RESULTS: The results show a significant difference between the PROD-SR risk symptom sum scores and the PROD-SR + I risk symptom sum scores (N = 395; Z = -15.123; P < 0.001). In an item-by-item analysis, the item 'Disorders in connection with hearing' had the strongest kappa value (0.827) agreement between an interviewed and self-report psychosis risk item. Agreement in most items remained between slight and substantial (kappa values from 0.082 to 0.649). CONCLUSIONS: The results suggest that there is a significant difference between psychosis risk symptom responses collected by self-report and self-report responses which are additionally confirmed by interview. Auditory disorders are the most reliably reported item with self-report.

Potencial cortical P3: nível de dificuldade para diferentes estímulos / P3 cortical potential: difficulty level for different stimulus

Objetivo Avaliar o nível de dificuldade de identificação dos estímulos verbais e não verbais, segundo classificação dos próprios participantes, e comparar com a latência do potencial cortical P3. Métodos Foram avaliados 30 sujeitos, com média de idade de 23 anos, normo-ouvintes. O potencial P3 foi pesquisado com estímulos não verbais (tone burst)e verbais (/ba/ x /di/, /ba/ x /ga/, /ba/ x /da/). Cada sujeito classificou os estímulos em "mais fácil" e "mais difícil".Resultados : A maioria dos indivíduos classificou o contraste /ba/ x /di/ como sendo o mais fácil de identificar e o contraste /ba/ x /ga/, como o mais difícil. Os sujeitos referiram que os estímulos de fala foram mais fáceis de identificar quando comparados com tone burst. O nível de dificuldade descrito pelos indivíduos influenciou nas latências dos estímulos /Di/ e /Da/, classificados como mais fáceis, e evidenciados na menor latência do P3.Conclusão O contraste /Ba/ x /Di/ foi considerado o de maior facilidade de percepção, sendo evidenciado pela menor latência do P3. Os contrastes de fala foram classificados mais fáceis quando comparados com os estímulos tonais. Essas comparações auxiliam o clínico na escolha do estímulo utilizado e no correto diagnóstico audiológico.

Purpose Evaluating the level of difficulty of identifying verbal and non-verbal stimuli, according to the classification of the participants, as well as comparing the latency of the P3 cortical potential.Methods Thirty subjects, with a mean age of 23 years and normal hearing, were evaluated. The P3 potential was performed with non-verbal stimuli (tone burst) and verbal (/ba/ x /di/, /ba/ x /ga/, /ba/ x /da/). Each subject had to classify stimulus in "the easiest" and "the most difficult".Results Most subjects rated the /ba/ x /di/ contrast as the easiest to identify and the contrast /ba/ x /ga/ the most difficult. The subjects reported that the speech stimulus were easier to identify when compared to tone burst. The difficulty level described by the subjects influenced the latencies of stimuli /Di/ and /Da/, ranked as the easiest and they were evidenced in the lowest latency of P3.Conclusion The /Ba/ x /Di/ contrast was considered the easiest for perception, being evidenced by the lowest latency of P3. The speech contrasts were classified as the easiest when compared with the tonal stimuli. These comparisons help the clinician in selecting the stimuli and in the correct audiological diagnosis.

Central auditory processing disorders in children and adults.

Central auditory processing disorders (CAPD) can affect children and adults of all ages due to a wide variety of causes. CAPD is a neurobiologic deficit in the central auditory nervous system (CANS) that affects those mechanisms that underlie fundamental auditory perception, including localization and lateralization; discrimination of speech and non-speech sounds; auditory pattern recognition; temporal aspects of audition, including integration, resolution, ordering, and masking; and auditory performance with competing and/or degraded acoustic signals (American Speech-Language-Hearing Association, 2005a, b). Although it is recognized that central auditory dysfunction may coexist with other disorders, CAPD is conceptualized as a sensory-based auditory disorder. Administration of behavioral and/or electrophysiologic audiologic tests that have been shown to be sensitive and specific to dysfunction of the CANS is critical for a proper diagnosis of CAPD, in addition to assessments and collaboration with a multidisciplinary team. Intervention recommendations for CAPD diagnosis are based on the demonstrated auditory processing deficits and related listening and related complaints. This chapter provides an overview of current definitions and conceptualizations, methods of diagnosis of, and intervention for, CAPD. The chapter culminates with a case study illustrating pre- and posttreatment behavioral and electrophysiologic diagnostic findings.

Future advances.

Future advances in the auditory systems are difficult to predict, and only educated guesses are possible. It is expected that innovative technologies in the field of neuroscience will be applied to the auditory system. Optogenetics, Brainbow, and CLARITY will improve our knowledge of the working of neural auditory networks and the relationship between sound and language, providing a dynamic picture of the brain in action. CLARITY makes brain tissue transparent and offers a three-dimensional view of neural networks, which, combined with genetically labeling neurons with multiple, distinct colors (Optogenetics), will provide detailed information of the complex brain system. Molecular functional magnetic resonance imaging (MRI) will allow the study of neurotransmitters detectable by MRI and their function in the auditory pathways. The Human Connectome project will study the patterns of distributed brain activity that underlie virtually all aspects of cognition and behavior and determine if abnormalities in the distributed patterns of activity may result in hearing and behavior disorders. Similarly, the programs of Big Brain and ENIGMA will improve our understanding of auditory disorders. New stem-cell therapy and gene therapies therapy may bring about a partial restoration of hearing for impaired patients by inducing regeneration of cochlear hair cells.

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.

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.

The neglected neglect: auditory neglect.

Whereas visual and somatosensory forms of neglect are commonly recognized by clinicians, auditory neglect is often not assessed and therefore neglected. The auditory cortical processing system can be functionally classified into 2 distinct pathways. These 2 distinct functional pathways deal with recognition of sound ("what" pathway) and the directional attributes of the sound ("where" pathway). Lesions of higher auditory pathways produce distinct clinical features. Clinical bedside evaluation of auditory neglect is often difficult because of coexisting neurological deficits and the binaural nature of auditory inputs. In addition, auditory neglect and auditory extinction may show varying degrees of overlap, which makes the assessment even harder. Shielding one ear from the other as well as separating the ear from space is therefore critical for accurate assessment of auditory neglect. This can be achieved by use of specialized auditory tests (dichotic tasks and sound localization tests) for accurate interpretation of deficits. Herein, we have reviewed auditory neglect with an emphasis on the functional anatomy, clinical evaluation, and basic principles of specialized auditory tests.

Xylene-induced auditory dysfunction in humans.

OBJECTIVES: Animal data indicate that xylene induces cochlear dysfunction, characterized by the loss of outer hair cells. There is little evidence regarding xylene-induced ototoxicity in humans. The aim of the study was to investigate the possible adverse effects of xylene on the peripheral and central auditory system in humans. DESIGN: A total of 30 medical laboratory workers who had been exposed to a mixture of xylene isomers, together with 30 nonexposed control participants matched for gender, age, and educational level were selected. Participants of both groups were not exposed to noise levels above 85 dBA time-weighted average. All participants were evaluated with a comprehensive audiological test battery, which included measures of peripheral and central auditory function. Peripheral auditory measures included pure-tone audiometry and distortion product otoacoustic emissions. Behavioral measures of central auditory function included a pitch pattern sequence test, an adaptive test of temporal resolution, a dichotic digit test, and a masking level difference test. The auditory brainstem response was used to objectively evaluate the function of the auditory pathways at the brainstem level. Speech perception in quiet and in noise was evaluated using the Hearing In Noise Test (HINT). The xylene-exposed participants were extensively evaluated with regard to their exposure to both noise and xylene. Noise dosimetry was conducted over an 8-hr work shift to obtain noise-exposure levels for each xylene-exposed worker. Airborne xylene concentrations were obtained at 11 different workstations throughout the medical laboratories, and methyl hippuric acid levels per gram of creatinine in urine were obtained for each xylene-exposed subject. Finally, a detailed interview exploring current and past solvent and noise exposure was conducted. RESULTS: The xylene-exposed participants showed significantly worse pure-tone thresholds in comparison with the nonexposed participants. The xylene-exposed participants demonstrated significantly worse results than the control group participants for the pitch pattern sequence test, dichotic digit test, HINT, and the auditory brainstem response (absolute and interpeak latencies). No significant differences between the xylene-exposed and nonexposed participants were observed for distortion product otoacoustic emissions, adaptive test of temporal resolution, or the masking level difference test. A significant correlation between the concentrations of methyl hippuric acid in urine and pure-tone thresholds (2 to 8 kHz) was found in xylene-exposed workers. Also, participants with high cumulative dose of xylene exposure presented with poorer test results than participants with low cumulative dose of xylene exposure. CONCLUSIONS: The results of the present research suggest that xylene is associated with adverse central auditory effects and poorer sound detection abilities in humans. A major limitation of the study is that the results found among xylene-exposed participants cannot be proved to be permanent, and thus further research should be conducted to clarify this limitation. Workers exposed to this chemical should be routinely evaluated with a comprehensive audiological test battery, to detect early signs of auditory dysfunction.

Waist circumference is associated with pitch pattern sequence score in older male adults.

OBJECTIVE: While obesity may increase the risk for neurodegenerative diseases such as Alzheimer's disease, the relationship between waist circumference (WC) and central auditory dysfunction is unknown. We aimed to investigate the relationship of WC and pitch pattern sequence (PPS) score in adults. DESIGN: The association of WC with PPS score was analysed. STUDY SAMPLE: Volunteer helpers at a community hospital, 391 adults ≥40 years, with normal or symmetrical sensorineural hearing loss were randomly selected. RESULTS: After adjusting for age, gender, pure-tone average, systemic diseases, and habits, WC was significantly negatively associated with PPS. In a subgroup analysis by gender and age, the PPS score was negatively associated with WC only for males who were older than 55 years old, but not for males who were younger than 55 years old or females in either age group. Meanwhile, central obesity showed positive association with abnormal PPS recognition ability (PPS score < 90%) of borderline significance only for males who were older than 55 years old, but not for males who were younger than 55 years old or females in both age groups. CONCLUSIONS: WC or central obesity is an independent risk factor for poor central auditory function, especially in older male subjects.

Prevalence and risk factors for auditory neuropathy spectrum disorder in a screened newborn population at risk for hearing loss.

OBJECTIVE: To determine the prevalence of Auditory Neuropathy Spectrum Disorder (ANSD) among infants with sensorineural hearing loss (SNHL) and discuss the risk factors. METHODS: The study group was comprised of children diagnosed with ANSD. Criteria for inclusion in the study group were as follows: permanent sensorineural hearing loss (SNHL); normal transient evoked or distortion product OAEs; absent or elevated middle-ear muscle reflexes (MEMR); severely abnormal or absent ABR waveform. All newborns were screened via a two-stage protocol, involving OAEs and ABR for the repeatedly referred cases and all neonates with one or more risk factors. RESULTS: From 2002 to 2011, 9419 infants whose hearing ability was uncertain or who had risk factors for hearing loss were investigated. From this population, 352 were diagnosed with SNHL. Of these 352 children, 18 (5.1%) were diagnosed with ANSD. In the ANSD group, prematurity and low birth weight (<1500 g) were observed in 5 cases; ototoxical medication in 8 cases; mechanical ventilation in excess of 5 days in 5 cases. Hyperbilirubinemia was observed in 7 cases, but severe hyperbilirubinemia requiring an exchange transfusion was not observed; 4 patients had no risk factors, 6 patients had only one risk factor, and the 8 remaining had two or more risk factors. CONCLUSION: Auditory Neuropathy Spectrum Disorder is not an extremely rare hearing disorder. Screening for hearing loss via OAEs, MEMR and ABR examinations concurrently are essential for the accurate diagnosis of ANSD.

Plasticity in the developing auditory cortex: evidence from children with sensorineural hearing loss and auditory neuropathy spectrum disorder.

The developing auditory cortex is highly plastic. As such, the cortex is both primed to mature normally and at risk for reorganizing abnormally, depending upon numerous factors that determine central maturation. From a clinical perspective, at least two major components of development can be manipulated: (1) input to the cortex and (2) the timing of cortical input. Children with sensorineural hearing loss (SNHL) and auditory neuropathy spectrum disorder (ANSD) have provided a model of early deprivation of sensory input to the cortex and demonstrated the resulting plasticity and development that can occur upon introduction of stimulation. In this article, we review several fundamental principles of cortical development and plasticity and discuss the clinical applications in children with SNHL and ANSD who receive intervention with hearing aids and/or cochlear implants.

Auditory function in children with Charcot-Marie-Tooth disease.

The peripheral manifestations of the inherited neuropathies are increasingly well characterized, but their effects upon cranial nerve function are not well understood. Hearing loss is recognized in a minority of children with this condition, but has not previously been systemically studied. A clear understanding of the prevalence and degree of auditory difficulties in this population is important as hearing impairment can impact upon speech/language development, social interaction ability and educational progress. The aim of this study was to investigate auditory pathway function, speech perception ability and everyday listening and communication in a group of school-aged children with inherited neuropathies. Twenty-six children with Charcot-Marie-Tooth disease confirmed by genetic testing and physical examination participated. Eighteen had demyelinating neuropathies (Charcot-Marie-Tooth type 1) and eight had the axonal form (Charcot-Marie-Tooth type 2). While each subject had normal or near-normal sound detection, individuals in both disease groups showed electrophysiological evidence of auditory neuropathy with delayed or low amplitude auditory brainstem responses. Auditory perception was also affected, with >60% of subjects with Charcot-Marie-Tooth type 1 and >85% of Charcot-Marie-Tooth type 2 suffering impaired processing of auditory temporal (timing) cues and/or abnormal speech understanding in everyday listening conditions.

Central auditory nervous system dysfunction in infants with non-syndromic cleft lip and/or palate.

OBJECTIVE: Peripheral hearing loss has been commonly reported in children with non-syndromic cleft lip and/or palate (NSCLP) but few studies have provided information about central auditory nervous system (CANS) functioning for this group. The main objective of this study was to explore CANS functioning in infants with NSCLP through analysis of auditory evoked potentials (AEPs). METHODS: AEPs including auditory brainstem response (ABR), middle latency response (MLR), and mismatch negativity (MMN) recordings were conducted in 34 infants of Chinese ethnicity with NSCLP and an equivalent number of normal controls. RESULTS: There was no significant difference in ABR (all measurements, including wave I, III, V latencies, I-V inter-wave latency, and wave V amplitude), or MLR (recordable components, Na, Pa latencies, and Na-Pa amplitude) findings between the two groups. However, infants with NSCLP had a significantly smaller MMN response than their normal controls, using MMN strength as the measurement. CONCLUSIONS: Significant abnormal auditory evoked potential findings at the cortical level suggest that infants with NSCLP may be at risk of central auditory discrimination dysfunction. Further effort is needed to determine auditory processing abilities in infants with NSCLP.