Background Due to small iron stores and rapid growth during the first months of life, infants with low birth weight (LBW) are at risk of iron deficiency (ID). ID in infancy is associated with irreversible impaired neurodevelopment. Preventive iron supplementation may reduce the risk of ID and benefit neurodevelopment, but there is also a possible risk of adverse effects. More than 50% of all LBW infants are born with marginally LBW (MLBW, 2000-2500g), and it is not known if they benefit from iron supplementation. Methods We randomized 285 healthy, Swedish, MLBW infants to receive 3 different doses of oral iron supplements; 0 (Placebo), 1, and 2 mg/kg/day from six weeks to six months of age. Iron status, during and after the intervention was assessed and so was the prevalence of ID and ID anemia (IDA), growth, morbidity and the interplay with iron and the erythropoetic hormones hepcidin and erythropoietin (EPO). As a proxy for conduction speed in the developing brain, auditory brainstem response (ABR) was analyzed at six months. In a follow up at 3.5 years of age, the children were assessed with a cognitive test (WPPSI-III) and a validated parental checklist of behavioral problems (CBCL), and compared to a matched reference group of 95 children born with normal birth weight. Results At six months of age, the prevalence of ID and IDA was significantly higher in the placebo group compared to the iron supplemented infants. 36% had ID in the placebo group, compared to 8% and 4 % in the 1 and 2mg/kg/day-groups, respectively. The prevalence of IDA was 10%, 3% and 0%, respectively. ABR-latencies did not correlate with the iron intake and was not increased in infants with ID or IDA. ABR wave V latencies were similar in all three groups. Hepcidin correlated to ferritin and increased in supplemented infants while EPO, which was negatively correlated to iron status indicators, decreased. At follow up there were no differences in cognitive scores between the groups but the prevalence of behavioral problems was significantly higher in the placebo group compared to those supplemented and to controls. The relative risk increase of CBCL-scores above a validated cutoff was 4.5 (1.4 – 14.2) in the placebo-group compared to supplemented children. There was no detected difference in growth or morbidity at any age. Conclusion MLBW infants are at risk of ID in infancy and behavioral problems at 3 years of age. Iron supplementation at a dose of 1-2 mg/kg/day from six weeks to six months of age reduces the risks with no adverse effects, suggesting both short and long term benefit. MLBW infants should be included in general iron supplementation programs during their first six months of life.

A ce jour, six millions de français sont atteints de troubles de l'audition. Face à ce problème de santé publique, des outils performants d'exploration de la fonction auditive sont indispensables. La Speech ABR (Speech Auditory Brainstem Response ou Réponse du tronc cérébral auditif à la parole) est un outil prometteur, comme marqueur électrophysiologique fin de l'encodage neuronal de la parole. Cependant, sa méthodologie reste peu développée, son origine neuronale incertaine et elle n'a jamais été enregistrée chez le malentendant porteur d'aides auditives. Le premier axe de cette thèse porte sur les générateurs neuronaux de la Speech ABR. Le développement d'une méthodologie de recueil topographique de cette réponse jusqu'alors décrite comme strictement sous-corticale, a d'abord suggéré la possibilité d'un générateur cortical. Une étude en stéréo-électroencéphalographie a ensuite confirmé l'existence d'une activité Speech ABR dans les cortex auditifs primaires bilatéraux. Ce résultat apporte un éclairage nouveau sur la représentation des sons de parole par système nerveux auditif. Le second axe concerne l'étude de la Speech ABR chez le malentendant appareillé. Après avoir développé une méthodologie de stimulation acoustique directement au travers des aides auditives, nous avons étudié la plasticité neuronale induite par le port d'aides auditives. Les résultats montrent une amélioration de l'identification des phonèmes amplifiés, liée à une représentation corticale modifiée et à un encodage fréquentiel rééquilibré. Ces toutes premières preuves de plasticité neuronales dès les 4 premiers mois d'utilisation des aides auditives ouvrent de nouveaux espoirs thérapeutiques / To date, six million French are hearing impaired. To address this public health issue, efficient tools for exploration of the hearing function are essentials. Speech ABR (Speech Auditory Brainstem Response) is a promising tool, being a fine electrophysiological marker of the neuronal encoding of speech. Though, its methodology remains underdeveloped, its neural origin is still uncertain, and it has never been recorded in hearing aid users. The first axis of this thesis focuses on the neural generators of Speech ABR. The development of a methodology for recording topographies of this response, up to now described as strictly subcortical, first suggested the possibility of a cortical generator. A stereo-electroencephalography study then confirmed the existence of Speech ABR activity in bilateral primary auditory cortices. This result sheds a new light on the representation of speech sounds within the auditory nervous system. The second axis concerns the study of Speech ABR in hearing aid users. After having developed a methodology of acoustic stimulation directly through hearing aids, we investigated neural plasticity induced by hearing aid use. Results show an improvement in the identification of amplified phonemes, linked to an altered cortical representation and a rebalanced frequency encoding. This very first evidence of neural plasticity as soon as the first four months of hearing aid use opens up new therapeutic hopes

There has always been a need for objective tests that assess auditory function in infants, young children, and/or any patient whose development level precludes the use of behavioral audiometric techniques. Although the Auditory Brainstem Response (ABR) is seen as the ‘gold standard’ in the field of objective audiometry, it presents with its own set of limitations. The Auditory Steady State Response (ASSR) has gained considerable attention and is seen as a promising addition to the AEP ‘family’ to address some of the limitations of the ABR. The ASSR promises to estimate all categories of hearing loss (mild to profound) in a frequency specific manner. It also indicates to the possibility to validate hearing aid fittings by determining functional gain of hearing aids by determining unaided and aided ASSR thresholds. An exploratory research design was selected in order to compare unaided thresholds, obtained through the use of three different procedures – ABR, ASSR and behavioral thresholds. Aided thresholds were also obtained and compared with two procedures – the aided ASSR (measured and predicted) and aided behavioral threshold. The results indicated that both the ABR (tone burst and click) and ASSR provided a reasonable estimation of the subsequently obtained behavioral audiograms. The ASSR, however, approximated the behavioral thresholds closer than the ABR and were furthermore able to quantify hearing thresholds accurately for subjects with severe and profound hearing losses. The result indicated further that the ASSR can be instrumental in the validation process of hearing aid fittings in infants. These results demonstrated however, that the ASSR measured thresholds underestimate the aided behavioral thresholds and the aided ASSR predicted thresholds overestimate the aided behavioral thresholds. The research concluded that the ASSR is useful in estimating frequency-specific behavioral thresholds accurately in infants and validating hearing aid fittings. Until evidence is sufficient to recommend the ASSR as primary electrophysiological measure of hearing in infants, the ASSR should be used in conjunction with the ABR – following a test battery approach in the diagnostic process of hearing loss in infants. The ASSR further shows great promise in validating hearing aid fittings, but this specific application of the ASSR needs further research evidence on large groups to validate the procedure. / Dissertation (Master of Communication Pathology)--University of Pretoria, 2007. / Speech-Language Pathology and Audiology / unrestricted

No description available.

Infant hearing screening (IHS) programs are not yet widespread in developing countries, such as South Africa. In order to ensure that the benefits of early hearing detection and intervention (EHDI) programs reach all infants, initial recommendations for the implementation of IHS programs in South Africa have been made by the Year 2002 Hearing Screening Position Statement by the Health Professions Council of South Africa. One of the platforms recommended for IHS in South Africa is the neonatal intensive care unit (NICU). South African NICU infants are at an increased risk for hearing loss, resultant of their high-risk birth histories, as well as the prevalence of context-specific environmental risk factors for hearing loss. There is currently a general scarcity of contextual data regarding the prevalence of risk indicators for hearing loss, and the prevalence of auditory impairment in the South African NICU population. The objective of this study was to describe an IHS program for NICU infants at a secondary hospital in Gauteng, South Africa. A quantitative descriptive research design was used to report on a cohort of 129 NICU infants followed up during a 29 month period. The objective of the study was achieved by describing the sample of infants in terms of the presence of specific risk indicators for hearing loss, the efficiency of the IHS program, and the incidence of auditory pathologies. Infants received their initial hearing screening as part of their medical and developmental follow-up visit at the hospital at three months of age. Routine rescreening visits were scheduled three monthly, whilst infants who failed the hearing screening were requested to return after three weeks for a follow-up. A data collection sheet was used to collect biographical information and risk indicators for hearing loss. Immittance measurements were recorded in the form of high-frequency and low-frequency tympanometry. Distortion product otoacoustic emissions (DPOAE) and automated auditory brainstem responses (AABR) were recorded, as well as diagnostic auditory brainstem responses (ABR) in cases where infants referred the screening protocol. Results revealed that environmental risk factors present in this sample included poor maternal education levels and prenatal HIV/AIDS exposure. At least 32% of mothers participating in this study did not complete high school. Prenatal HIV/AIDS exposure was present in at least 21% of the current sample of infants. The screening coverage rate fell short of the 95% benchmark set by the Joint Committee on Infant Hearing (JCIH, 2000). A 67% coverage rate was achieved with AABR screening, and an 88% coverage rate was achieved with DPOAE screening. 93% of infants had immittance screening performed on their initial visit to the IHS program. According to the Fisher’s two-sided exact test and the logistic regression procedure, high frequency tympanometry proved to be more effective than low frequency tympanometry, when assessing the middle ear functioning of infants younger than seven months when compared with DPOAE results. Normative pressure and admittance data was compiled for the use of high frequency tympanometry in NICU infants. Poor follow-up rates were recorded for both routine and non-routine visits, but are expected to improve over time. Furthermore, results indicated a high incidence of hearing impairment. Permanent congenital hearing loss was identified in 3% (n=4) of the sample. Half of these presented with sensorineural hearing loss, whilst the other half had auditory neuropathy. The incidence of auditory impairment is estimated to be 3.75% if the percentage of infants who did not return for follow-up is taken into account. A high incidence of middle ear pathology was recorded, with an incidence rate of 60.4%, including bilateral and unilateral middle ear pathology. The high prevalence of auditory impairment in South African NICU infants, and the lack of widespread IHS programs, indicates that many vulnerable infants are being the denied the benefits of early identification of and intervention for hearing loss. The implementation of widespread IHS programs in South Africa is therefore essential, in order to ensure that all South African infants receive the benefits of EHDI programs. / Dissertation (MCommunication Pathology)--University of Pretoria, 2007. / Speech-Language Pathology and Audiology / unrestricted

Introduction: Auditory neuropathy spectrum disorder (ANSD) is a disorder characterized by impaired temporal coding of acoustic signals due to a deficiency in neural synchrony or neural transmission. Despite variations in speech perception outcomes within both patients and studies, current evidence demonstrates that children with ANSD, who use hearing aids (HAs) or cochlear implants (CIs), generally achieve speech perception performance comparable to peers with sensorineural hearing loss (SNHL). However, limited studies have reported factors that have prognostic value for auditory intervention outcomes. The objectives of this doctoral thesis, consisting of three consecutive associated projects on children with ANSD, were (1) to determine factors with predictive value for post-intervention (CIs and/or HAs) outcomes through a retrospective study, (2) to systematically summarize and critically appraise existing evidence of the prognostic value of early auditory electrophysiologic tests and MRI findings for CI outcomes through a systematic review (SR), and (3) to systematically overview, summarize, and critically appraise evidence of CI outcomes through an umbrella review of current SRs (overview of SRs). -- Methods: For the first project, the records of 38 children with ANSD between 5 and 18 years old, 63.20% males, who used CIs (71%) and/or HAs, identified at the Children's Hospital of Eastern Ontario (CHEO) were reviewed. For the second and third projects, the SRs were guided by the PRISMA 2020 statement, and electronic databases were searched without restrictions on language, publication status, or year of publication. In the second project, studies on children with ANSD (including those with cochlear nerve deficiency [CND]), cochleovestibular nerve (CVN) abnormalities, or SNHL reporting the relevance of preoperative and/or postoperative electric compound action potential (eCAP), electric auditory brainstem response (eABR), and/or MRI results to CI outcomes were included. The methodological quality and strength of evidence were assessed using the Crowe Critical Appraisal Tool (CCAT) and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool, respectively. In the third project, all SRs that reported CI outcomes in children with ANSD were included. The methodological quality of the selected SRs was evaluated using the Assessment of Multiple Systematic Reviews 2 (AMSTAR-2) checklist, and the risk of bias in evidence was assessed using the Risk of Bias in Systematic Reviews (ROBIS) tool. -- Results: In the retrospective chart review (first project), ages at HL diagnosis and CI activation and the length of follow-up with CI/HA showed a significant relationship with open-set speech perception outcomes (i.e., the scores of Phonetically Balanced Kindergarten [PBK] test with word and phoneme speech materials and Hearing in Noise Test [HINT] in quiet and noise conditions). Using a Forward Linear Multiple Regression Model, the length of follow-up with CI/HA and bilateral amplification showed prognostic value for speech perception performance. In the second project, 25 papers were included in the review. While it was difficult to draw a firm conclusion about the eCAP findings, current evidence strongly supports the prognostic value of eABR and MRI for post-CI speech perception outcomes. According to the eight SRs selected for the third project, children with ANSD achieve CI outcomes comparable to their peers with SNHL. However, in children with postsynaptic ANSD (i.e., those with CND), cochlear nerve hypoplasia is associated with better speech recognition outcomes compared to cochlear nerve aplasia, especially in the absence of additional disabilities and/or medical comorbidities (ADs/MCs). -- Conclusion: Children with ANSD, especially those without cochlear nerve aplasia and ADs/MCs, achieve speech perception outcomes comparable to their peers with SNHL. In addition, age at HL diagnosis, age at CI activation, the length of follow-up with CI/HA, bilateral amplification, and eABR and MRI findings are associated with or have predictive value for intervention outcomes. The findings of the SRs should be interpreted with caution given the low quality of evidence and risk of bias in the studies selected for SRs.

No description available.