There is a higher prevalence of hearing loss in children with diagnosed neurological disorders than the general paediatric population. It is therefore essential that these children have their hearing assessed. Conventional behavioural audiometry requires participation from the child, and in a majority of this population with neurological pathology this is not always possible owing to their neurocompromised state. These children will have to undergo objective testing, such as the Auditory Brainstem Response (ABR) in order to obtain estimated hearing thresholds, as this requires no active involvement from the patient. This study therefore aims to describe the audiological ABR findings in order to determine hearing function in this group and to establish a relationship between audiological ABR findings to behavioural audiometry findings where these exist in a group of neurologically disordered children in a tertiary hospital in South Africa. Methods: A retrospective review was conducted on 40 ABR patient records of children between the ages of 5 months and 10 years diagnosed with a neurological disorder. Behavioural audiometry results were then sought for these children, where these existed. Hearing status was described for each child per ear for both objective and behavioural results, and descriptive statistics were conducted. Results: 56.25 % (n=45) of ears in this study presented with normal hearing on ABR testing. No behavioural audiometry results were obtained in 72.5 % (n=58) of ears in this study. Results correlated between ABR and behavioural testing for only 7.5% (n=8) of ears tested and in all eight of these ears the hearing result was within normal hearing limits. Twelve and a half percent (n=10) of ears were misdiagnosed on behavioural testing. More premature infants were able to be tested behaviourally when compared to other pathologies. Cerebral palsy, Down’s Syndrome, prematurity and RVD were the pathologies in which the most hearing losses were diagnosed. Conclusions: Behavioural audiometry appears a largely unreliable method of hearing testing in children diagnosed with neurological disorders as results were obtained in only 27.5 % of the study sample; however it remains the gold standard in paediatric hearing testing in order to evaluate the entire auditory system and provides information on how a child processes sound, unlike ABR testing which only provides hearing information up to the auditory brainstem. This study highlights the high prevalence of hearing problems in children with neurological disorders and therefore the importance of hearing testing in this population. Hearing thresholds should be established for subsequent remediation via objective testing. Conditioning should continue simultaneously for a behavioural audiological test battery with adaptations for the child’s developmental ability.

ABSTRACT It is well documented that repetitive exposures to high intensity sound can cause acoustic trauma to the ear resulting in hearing loss, and that occupational noise is a significant cause of adult-onset hearing loss. Research world wide has indicated a significant number of workers with hearing loss attributed to noise exposure. Noise-Induced Hearing Loss (NIHL) claims are responsible for the majority of occupational disease payouts. The study was undertaken in order to determine the extent of hearing loss due to noise exposure that could be ascribed to excessive exposure to noise, and to describe the noise-induced hearing loss by severity, type of work, and area of work and duration of service. The cross-sectional study included 466 workers employed in a pulp and paper mill in KwaZulu Natal (KZN) South Africa. It involved the assessment of 932 individual audiograms to diagnose noise-induced hearing loss and the calculation of the percentage loss of hearing from pre placement to the year 2005. Audiometry results were presented for noise-induced hearing loss in relation to area of work, duration of service, categories of severity and age group. The prevalence of noise-induced hearing loss in the pulp and paper mill was 21% (98/466) and with 79% (368/466) of workers whose audiograms returned results not indicating NIHL. 75 workers were excluded due to workplace transfers. Type of work, area of work and years of service correlated significantly with a diagnosis of noise-induced hearing loss. As a department, the wood yard (which included the wood chipping facility, maintenance workers and workers with 10 – 20 years of service) showed the most significant association. In categories of severity 16.7% of workers suffering from NIHL fall in the ≤ 5 Percentage Loss of Hearing PLH category. This study has confirmed the findings of others that noise exposure is a significant hazard in industry and an effective noise control programme is the only way to reduce the risk of NIHL. _____________________________________________________________________

Os estados do Nordeste brasileiro concentram elevadas taxas de pessoas com deficiências, mas pouco se estudou a respeito de suas causas. O objetivo desse estudo foi determinar a prevalência da deficiência auditiva e estimar a contribuição dos fatores genéticos na sua etiologia nas populações de dois municípios do Nordeste brasileiro. Após indicação pelos agentes comunitários de saúde para avaliação clínico-genética, foram avaliados 182 indivíduos com perda auditiva manifestada antes dos 60 anos dos municípios de Gado Bravo (76 pacientes) e Queimadas (106 pacientes), com população de 8.376 e 41.049 habitantes, respectivamente. Em Queimadas, 13 pacientes eram homozigotos com a mutação c.35delG no gene GJB2 (13/106, 12,2%; 6/81, 7,4% das famílias). Já em Gado Bravo, somente um paciente era homozigoto com esta mutação (1/76, 1,3%; 1/55, 1,8% das famílias). A mutação m.A1555G no gene mitocondrial MTRNR1 e a mutação c.167delT no gene GJB2 não foram detectadas em ambos os municípios. Quanto às deleções do GJB6, apenas a del(GJB6-D13S1854) foi encontrada em quatro casos em Gado Bravo (4/76, 5,3%; 2/55, 3,6% das famílias). Após o sequenciamento completo do gene GJB2, foi detectada a mutação p.W24X (c.G71A) em heterozigose em três casos isolados do município de Gado Bravo (3/76, 3,9%). Em resumo, mutações patogênicas no lócus DNFB1 foram encontradas em 16% (34/212) dos alelos testados no município de Queimadas e em 9,9% (15/152) dos alelos testados no município de Gado Bravo. No total da casuística, ocorreram 11 pacientes com uma única mutação recessiva detectada (monoalélica) no lócus DFNB1. As amostras desses 11 pacientes foram submetidas à análise de MLPA na tentativa de identificar uma segunda mutação, do tipo variação do número de cópias, mas nenhuma mutação foi encontrada. O gene SLC26A4 foi sequenciado em amostras de famílias com padrão de herança autossômico recessivo sem mutação detectada no lócus DFNB1, que apresentaram ligação compatível por meio de microssatélites na região próxima a esse gene. Não foi detectada nenhuma mutação patogênica na região de código desse gene. Após o estudo de ligação por meio de array de SNPs e microssatélites em uma família com quatro afetados pela síndrome de Usher do município de Gado Bravo, o gene CLRN1 apareceu como provável candidato e as amostras desses pacientes foram selecionadas para sequenciamento. Foi detectada a mutação p.Y63X em homozigose nos quatro pacientes. As amostras dos outros pacientes com essa síndrome também foram sequenciadas. Essa mutação foi encontrada em homozigose em 21 dos 23 casos de síndrome de Usher em Gado Bravo. A porcentagem de casos de surdez com provável etiologia genética em Gado Bravo e Queimadas foi estimada em 55% e 45%, respectivamente / The states of the Brazilian Northeast concentrate high rates of people with disabilities, but little has been investigated about their causes. The aim of this study was to determine the prevalence of hearing impairment and estimate the contribution of genetic factors in its etiology in populations from two counties in the Northeast of Brazil. After indication from community health agents, 182 individuals were evaluated, presenting hearing loss before the age of 60 in the counties of Gado Bravo (76 patients) and Queimadas (106 patients), with populations of 8,376 and 41,049 inhabitants, respectively. In Queimadas, 13 homozygotes with the c.35delG mutation in the GJB2 gene were found (13/106, 12.2%, 6/81, 7.4% of probands). As for Gado Bravo (N = 76), only one patient was homozygous with this mutation (1/76, 1.3%, 1/55, 1.8% of probands). The m.A1555G mutation in the mitochondrial gene MTRNR1, and the c.167delT mutation in the GJB2 gene were not detected in both counties. As for GJB6 deletions, only the del(GJB6-D13S1854) was found in four cases from Gado Bravo (4/76, 5.3%, 2/55, 3.6% of probands). After the complete sequencing of the GJB2 gene, the p.W24X (c.G71A) mutation was detected in three isolated heterozygous cases of the Gado Bravo county (3/76, 3.9%). In two of these cases, the mutation was present along with a second recessive mutation in the DNFB1 locus. In short, pathogenic mutations in the DNFB1 locus were found in 16% (34/212) of the alleles tested in the county of Queimadas and 9.9% (15/152) of the alleles tested in the county of Gado Bravo. No pathogenic mutation was detected in the coding region of this gene. From all cases, there were 11 patients with a single recessive mutation detected (monoallelic) in DFNB1 locus. Samples of these 11 patients were analyzed for MLPA in attempt to identify a second mutation, with copy number variation, but no mutation was found. The SLC26A4 gene was sequenced in families samples with autosomal recessive hearing loss, with no mutation detected in the DFNB1 locus, presenting compatible linkage utilizing microsatellites near this gene region. After linkage study using SNPs arrays and microsatellites in a family with four affected by the Usher syndrome in Gado Bravo, the CLRN1 gene appeared as a candidate and samples of these patients were selected for sequencing. The p.Y63X mutation was detected in the homozygosis in the four individuals. Samples from other patients with this syndrome were also sequenced and this mutation was found in homozygosis 21 out of 23 cases of Usher syndrome in Gado Bravo. The percentage of cases with a probable genetic cause for hearing loss in Gado Bravo and Queimadas was estimated at 55% and 45%, respectively.

Os estados do Nordeste brasileiro concentram elevadas taxas de pessoas com deficiências, mas pouco se estudou a respeito de suas causas. O objetivo desse estudo foi determinar a prevalência da deficiência auditiva e estimar a contribuição dos fatores genéticos na sua etiologia nas populações de dois municípios do Nordeste brasileiro. Após indicação pelos agentes comunitários de saúde para avaliação clínico-genética, foram avaliados 182 indivíduos com perda auditiva manifestada antes dos 60 anos dos municípios de Gado Bravo (76 pacientes) e Queimadas (106 pacientes), com população de 8.376 e 41.049 habitantes, respectivamente. Em Queimadas, 13 pacientes eram homozigotos com a mutação c.35delG no gene GJB2 (13/106, 12,2%; 6/81, 7,4% das famílias). Já em Gado Bravo, somente um paciente era homozigoto com esta mutação (1/76, 1,3%; 1/55, 1,8% das famílias). A mutação m.A1555G no gene mitocondrial MTRNR1 e a mutação c.167delT no gene GJB2 não foram detectadas em ambos os municípios. Quanto às deleções do GJB6, apenas a del(GJB6-D13S1854) foi encontrada em quatro casos em Gado Bravo (4/76, 5,3%; 2/55, 3,6% das famílias). Após o sequenciamento completo do gene GJB2, foi detectada a mutação p.W24X (c.G71A) em heterozigose em três casos isolados do município de Gado Bravo (3/76, 3,9%). Em resumo, mutações patogênicas no lócus DNFB1 foram encontradas em 16% (34/212) dos alelos testados no município de Queimadas e em 9,9% (15/152) dos alelos testados no município de Gado Bravo. No total da casuística, ocorreram 11 pacientes com uma única mutação recessiva detectada (monoalélica) no lócus DFNB1. As amostras desses 11 pacientes foram submetidas à análise de MLPA na tentativa de identificar uma segunda mutação, do tipo variação do número de cópias, mas nenhuma mutação foi encontrada. O gene SLC26A4 foi sequenciado em amostras de famílias com padrão de herança autossômico recessivo sem mutação detectada no lócus DFNB1, que apresentaram ligação compatível por meio de microssatélites na região próxima a esse gene. Não foi detectada nenhuma mutação patogênica na região de código desse gene. Após o estudo de ligação por meio de array de SNPs e microssatélites em uma família com quatro afetados pela síndrome de Usher do município de Gado Bravo, o gene CLRN1 apareceu como provável candidato e as amostras desses pacientes foram selecionadas para sequenciamento. Foi detectada a mutação p.Y63X em homozigose nos quatro pacientes. As amostras dos outros pacientes com essa síndrome também foram sequenciadas. Essa mutação foi encontrada em homozigose em 21 dos 23 casos de síndrome de Usher em Gado Bravo. A porcentagem de casos de surdez com provável etiologia genética em Gado Bravo e Queimadas foi estimada em 55% e 45%, respectivamente / The states of the Brazilian Northeast concentrate high rates of people with disabilities, but little has been investigated about their causes. The aim of this study was to determine the prevalence of hearing impairment and estimate the contribution of genetic factors in its etiology in populations from two counties in the Northeast of Brazil. After indication from community health agents, 182 individuals were evaluated, presenting hearing loss before the age of 60 in the counties of Gado Bravo (76 patients) and Queimadas (106 patients), with populations of 8,376 and 41,049 inhabitants, respectively. In Queimadas, 13 homozygotes with the c.35delG mutation in the GJB2 gene were found (13/106, 12.2%, 6/81, 7.4% of probands). As for Gado Bravo (N = 76), only one patient was homozygous with this mutation (1/76, 1.3%, 1/55, 1.8% of probands). The m.A1555G mutation in the mitochondrial gene MTRNR1, and the c.167delT mutation in the GJB2 gene were not detected in both counties. As for GJB6 deletions, only the del(GJB6-D13S1854) was found in four cases from Gado Bravo (4/76, 5.3%, 2/55, 3.6% of probands). After the complete sequencing of the GJB2 gene, the p.W24X (c.G71A) mutation was detected in three isolated heterozygous cases of the Gado Bravo county (3/76, 3.9%). In two of these cases, the mutation was present along with a second recessive mutation in the DNFB1 locus. In short, pathogenic mutations in the DNFB1 locus were found in 16% (34/212) of the alleles tested in the county of Queimadas and 9.9% (15/152) of the alleles tested in the county of Gado Bravo. No pathogenic mutation was detected in the coding region of this gene. From all cases, there were 11 patients with a single recessive mutation detected (monoallelic) in DFNB1 locus. Samples of these 11 patients were analyzed for MLPA in attempt to identify a second mutation, with copy number variation, but no mutation was found. The SLC26A4 gene was sequenced in families samples with autosomal recessive hearing loss, with no mutation detected in the DFNB1 locus, presenting compatible linkage utilizing microsatellites near this gene region. After linkage study using SNPs arrays and microsatellites in a family with four affected by the Usher syndrome in Gado Bravo, the CLRN1 gene appeared as a candidate and samples of these patients were selected for sequencing. The p.Y63X mutation was detected in the homozygosis in the four individuals. Samples from other patients with this syndrome were also sequenced and this mutation was found in homozygosis 21 out of 23 cases of Usher syndrome in Gado Bravo. The percentage of cases with a probable genetic cause for hearing loss in Gado Bravo and Queimadas was estimated at 55% and 45%, respectively.

Ménière's disease (MD) is a complex disorder of the inner ear characterized by the symptoms of hearing loss, tinnitus, and vertigo, with an incidence in Caucasians of one in 1000. The hallmark histopathologic feature of MD is endolymphatic hydrops. Symptoms of MD typically present in the fourth decade of life, and the vertigo attacks experienced by patients with MD can be debilitating. Treatments aimed at alleviating the symptoms of MD are ineffective in approximately 30% of patients. Several studies have attempted to identify genetic factors important in MD through the use of families segregating the disease, but causative genes have not been identified. Many of these studies have been unsuccessful due to the fact that families of sufficient size to generate meaningful linkage results are extremely rare. Attempts to identify a genetic component to MD through the use of candidate gene association studies have been underpowered or poorly designed and therefore also unsuccessful. We hypothesize Ménière's disease is a complex disorder that is due to the interplay of genetic and environmental factors. We tested this hypothesis using linkage and association studies. Initially, we focused on candidate gene replication association studies (KCNE1, KCNE3, iNOS), as well as testing a novel candidate gene (AQP4). We were unable to replicate the previous associations and although we could not identify an association between MD and AQP4 we did discover rare variants of AQP4 in our MD patient population. These variants segregate with a `syndromic' MD phenotype. We also performed a genome-wide linkage study on a large Chilean family segregating MD over three generations and identified a novel MD locus on 1q32.1-1q32.3. Targeted exon capture and pyrosequencing of the region identified two potential disease-causing variants in two genes of unknown function. We next screened a cohort of singleton patients with MD for variants in these same genes. Surprisingly, in both genes, we identified common and rare variants supporting a possible role for either gene in the development of MD. The function of these two genes is unknown. Our results imply that additional studies must be undertaken to determine whether one or both genes has a role in the pathogenesis of MD. Identification of a causative gene will aid in the understanding of disease pathophysiology and lead to improved treatments.

No description available.

The aim of this study was to determine in an empirical manner whether the phenomenon of hearing loss due to the exposure to volatile organic solvents was present in the gasification plants of a petrochemical factory. The experimental groups included unexposed (N=20) workers, workers (N=20) exposed to noise and workers (N=19) exposed to noise and volatile organic solvents. The following assessments were made: diagnostic audiometry for the assessment of hearing thresholds; biological monitoring of ortho-cresol and hippuric acid for the biological markers of toluene; passive air sampling and noise measurements. Questionnaires were completed by the three groups to collect information about age, ethnicity, smoking habits, alcohol consumption and work history regarding the exposure to ototoxic substances as well as the period of employment. There were no statistically significant differences between the average ages of the three groups, but more of the workers in the noise group were from a higher age group. This age composition and the work history of the noise group were considered as possible influences on the results of this hearing study. The results of the passive air sampling show that the levels of volatile organic solvents were lower than the occupational exposure limits on the day of sampling. The biological monitoring shows that the markers, namely hippuric acid and o-cresol, were lower than the biological exposure indices. The noise group was exposed to sound pressure levels of 79-90 dB(A) and the noise + hydrocarbon group to levels of 85-88 dB(A). The average hearing thresholds of the noise group were at most of the frequencies (0.5-8 kHz) significantly higher (p≤0,05) than that of the noise + hydrocarbon group. The average hearing thresholds of the control group were overall lower than the noise group's hearing thresholds, but on average a little higher than the noise + hydrocarbon group's hearing thresholds. No relationship was found in this study between the exposure to volatile organic solvents (for example toluene that was used as marker in this study) and the elevation of hearing thresholds of workers at the gasification plants of the petrochemical factory. / Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.

Objective: The primary purpose of this study was to determine the influence of high frequency peripheral hearing loss on test performance on the University of Canterbury Adaptive Speech Test – Filtered Words (UCAST-FW). We also aimed to investigate (1) if there is an ear advantage in performing the UCAST-FW; (2) whether there is any correlation between the UCAST-FW score and age; (3) the effectiveness of a binaural practice run in reducing the learning effect; and (4) the average time required for older adults to complete the UCAST-FW. Method: A total of 18 participants with normal hearing (≤ 25 dB Hearing Level (HL) at octave intervals of 250 through 4000 Hz in both ears) and 19 participants with varying degrees of high frequency sensorineural hearing loss (>25 dB HL at frequencies above 1000 Hz) were included in this study. All participants were native New Zealand English speakers, aged between 55-71 years, with normal low frequency hearing (≤25 dB at 250, 500 and 1000 Hz), had speech scores consistent with their audiogram, normal cognition and judged by the examiner to be capable of completing test protocols in terms of sufficient eyesight, alertness and motor control. Participants underwent a full diagnostic hearing test, the Montreal Cognitive Assessment, the Dichotic Digits Test, the Random Gap Detection Test and the UCAST-FW. Results: Findings indicated that the presence of a high frequency peripheral hearing loss had no significant influence on the UCAST-FW score. Findings also showed no significant ear advantage, or any trend between the participant’s UCAST-FW score and their age. A binaural practice run comprised of 5 initial and 15 working reversals was effective in reducing any learning effect. The UCAST-FW took an average of 15 minutes to complete, and the results showed no correlation between the test completion time and the participant’s age. Conclusion: Findings suggested that the listener’s high frequency peripheral hearing sensitivity had no significant influence on their UCAST-FW score and thus the UCAST-FW can potentially be an effective test for assessing Auditory Processing Disorder (APD) in older adults and the elderly regardless of their high frequency peripheral hearing sensitivity. The development of test material in New Zealand English, as well as the investigation of the validity of the UCAST-FW in assessing APD in older adults and the influence of cognitive functioning on test performance is necessary before the UCAST-FW can be implemented in New Zealand clinical Audiology settings.

The aim of this study was to determine in an empirical manner whether the phenomenon of hearing loss due to the exposure to volatile organic solvents was present in the gasification plants of a petrochemical factory. The experimental groups included unexposed (N=20) workers, workers (N=20) exposed to noise and workers (N=19) exposed to noise and volatile organic solvents. The following assessments were made: diagnostic audiometry for the assessment of hearing thresholds; biological monitoring of ortho-cresol and hippuric acid for the biological markers of toluene; passive air sampling and noise measurements. Questionnaires were completed by the three groups to collect information about age, ethnicity, smoking habits, alcohol consumption and work history regarding the exposure to ototoxic substances as well as the period of employment. There were no statistically significant differences between the average ages of the three groups, but more of the workers in the noise group were from a higher age group. This age composition and the work history of the noise group were considered as possible influences on the results of this hearing study. The results of the passive air sampling show that the levels of volatile organic solvents were lower than the occupational exposure limits on the day of sampling. The biological monitoring shows that the markers, namely hippuric acid and o-cresol, were lower than the biological exposure indices. The noise group was exposed to sound pressure levels of 79-90 dB(A) and the noise + hydrocarbon group to levels of 85-88 dB(A). The average hearing thresholds of the noise group were at most of the frequencies (0.5-8 kHz) significantly higher (p≤0,05) than that of the noise + hydrocarbon group. The average hearing thresholds of the control group were overall lower than the noise group's hearing thresholds, but on average a little higher than the noise + hydrocarbon group's hearing thresholds. No relationship was found in this study between the exposure to volatile organic solvents (for example toluene that was used as marker in this study) and the elevation of hearing thresholds of workers at the gasification plants of the petrochemical factory. / Thesis (M.Sc.)--North-West University, Potchefstroom Campus, 2004.

No description available.