Sensorineural hearing loss

Individual differences in visual pattern completion predict adaptation to degraded speech

Recognizing acoustically degraded speech relies on predictive processing whereby incomplete auditory cues are mapped to stored linguistic representations via pattern recognition processes. While listeners vary in their ability to recognize degraded speech, performance improves when a written transcription is presented, allowing completion of the partial sensory pattern to preexisting representations. Building on work characterizing predictive processing as pattern completion, we examined the relationship between domain-general pattern recognition and individual variation in degraded speech learning. Participants completed a visual pattern recognition task to measure individual-level tendency towards pattern completion. Participants were also trained to recognize noise-vocoded speech with written transcriptions and tested on speech recognition pre- and post-training using a retrieval-based transcription task. Listeners significantly improved in recognizing speech after training, and pattern completion on the visual task predicted improvement for novel items. The results implicate pattern completion as a domain-general learning mechanism that can facilitate speech adaptation in challenging contexts.

The Importance of Lassa Fever and Its Disease Management in West Africa

Lassa virus (LASV) is a zoonotic pathogen endemic throughout western Africa and is responsible for a human disease known as Lassa fever (LF). Historically, LASV has been emphasized as one of the greatest public health threats in West Africa, with up to 300,000 cases and 5000 associated deaths per year. This, and the fact that the disease has been reported in travelers, has driven a rapid production of various vaccine candidates. Several of these vaccines are currently in clinical development, despite limitations in understanding the immune response to infection. Alarmingly, the host immune response has been implicated in the induction of sensorineural hearing loss in LF survivors, legitimately raising safety questions about any future vaccines as well as efficacy in preventing potential hearing loss. The objective of this article is to revisit the importance and prevalence of LF in West Africa, with focus on Nigeria, and discuss current therapeutic approaches and ongoing vaccine development. In addition, we aim to emphasize the need for more scientific studies relating to LF-associated hearing loss, and to promote critical discussion about potential risks and benefits of vaccinating the population in endemic regions of West Africa.

The results of newborn hearing screening by means of transient otoacoustic emissions - has anything changed over 10 years?

OBJECTIVES

Universal newborn hearing screening (UNHS) has become the standard of care in many countries. The aim of this study was to evaluate the results of UNHS after ten years of the program in Poland and to compare them with the results of 2003.

METHODS

In the study, we analyze the results of UNHS in the University Hospital in Poznan, Poland. Between 01.01.2013 and 31.12.2013, 6827 children were examined by means of otoacoustic emissions.

RESULTS

Risk factors (RF) were identified in 772 (11.3%) newborns, which is significantly less than 10 years ago (p < 0.05). The most frequent RF were: ototoxic medications, treatment in neonatal intensive care unit (NICU) and prematurity < 33 weeks of gestation. In 2003, the most frequent were ototoxic medications and prematurity, less frequent was treatment in NICU and more common was low Apgar score. In 51 (6.6%) newborns with RF, the result of OAE was positive either unilaterally or bilaterally. In infants without RF the result was positive unilaterally in 22 (0.4%) and bilaterally in 14 (0.2%) patients. These results are significantly lower than in our former study. The relative risk of positive result was the highest in infants with complex congenital anomalies (RR = 44.99), craniofacial anomalies (RR = 17.46) and mechanical ventilation for > 5 days (RR = 10.69). In our previous study, the highest RR of positive test results was in infants with family history, congenital malformations and low Apgar score. We found that most predictive as to the final diagnosis was bilaterally positive OAE test. In most patients, the second check confirmed the diagnosis, independently of RF. The number of false positive tests at the 1st level of screening is significantly lower now than 10 years ago, probably due to better staff training.

CONCLUSIONS

Long term monitoring and the appropriate management of hearing deficit in children is essential. UNHS seems to be the most efficient way of finding children who require treatment of hearing impairment. The prevalence of most risk factors of hearing deficit has significantly changed over the years. The number of false positive results has significantly decreased over the years thanks to better staff training.

Screening for Hearing Impairment in High Risk Neonates: A Hospital Based Study

BACKGROUND

Hearing loss very early in life can have multiple deleterious effects on the new born most commonly being related to attainment of speech and language. Also, it can affect social, emotional and academic achievement of the child.Early identification of hearing impairment has been shown to improve prognosis and hence screening programs have been widely and strongly advocated.

AIMS AND OBJECTIVES

To estimate the incidence of neonatal hearing loss in high risk neonates admitted in tertiary level teaching hospital and to determine the risk factors predictive of hearing impairment in them.

MATERIALS AND METHODS

It was a prospective study over a period of one year. We screened high risk neonates for hearing impairment admitted to NICU using Brain stem Auditory Evoked Response (BAER).The morphology of the response and wave and interwave latencies was examined in respect to age-appropriate forms. Follow up BAER after one month was performed in cases where initial BAER was abnormal. Babies who tested abnormal on the follow-up were referred for detailed audiology diagnostic work up.

RESULTS

A total of 200 cases comprising 118 males (59%) and 82 females (41%) were enrolled. On initial BAER testing, 18 (15.25%) males and 14 (17%) female neonates had hearing loss. Whereas 7 males (70%) and 3 females (30%) had hearing loss out of the total 10 hearing loss cases in the Follow up-BAER testing. Two out of the 6 neonates with birth weight <1500g had hearing loss in the follow up of BAER testing. Use of ototoxic medications, hyperbilirubinemia requiring exchange transfusion, perinatal asphyxia and bacterial meningitis were the major risk factors occurring in 45%, 30% and 26% and 10%. Five neonates had unilateral hearing loss and the rest five (5%) had bilateral impairment.Meningitis was the significant independent clinical risk factors for predicting hearing impairment in high risk neonates.The risk of BAER increased cumulatively with BAER abnormality rate of 4.2%, 22.2% and 33.3% with one two and three risk factors respectively.

CONCLUSION

The overall incidence of hearing loss in initial BERA testing was 16%, in males it was 15.25% in males and in 17% in females,only 62.5% of neonates had a persistent abnormal BAER, with male gender a significant risk factor for this. The incidence of hearing loss increased with number of risk factors. The study highlights that although universal hearing screening programs are warranted; most newborns with a detected hearing loss can be identified based on the risk factors. Thus, a targeted approach for hearing screening may be more feasible in resource limited settings.

Neonatal hearing screening in Albania: Results from an ongoing universal screening program

The paper describes the outcomes of an ongoing universal hearing screening program in Tirana, Albania. The main objectives of the project were the evaluation of the feasibility of a neonatal hearing screening program in Albania, and an evaluation of the prevalence of risk factors in the NICU environment. One thousand five hundred and sixty-one (1561) infants from both the WB and NICU were screened with transient evoked otoacoustic emissions (TEOAE). A detailed history of risk factors was collected in each case, thus it was possible to evaluate the main factors influencing the output of the screening program. It was concluded that the program had the capacity to identify infants with congenital hearing loss provided that an informative component is well-structured and delivered. Also, although the prevalence of risk factors appeared high, the reduction of 'case leakage' would allow the precise estimation of the incidence of hearing loss in the Albanian population.

Hearing loss in children with very low birth weight: current review of epidemiology and pathophysiology

An association between birth weight <1500 g (very low birth weight (VLBW)) and hearing loss has been long recognised. As universal hearing screening programmes have become widely implemented and the survival rate of VLBW babies in modern intensive care units has increased, we have gained a substantially better understanding of the nature of this problem. However, many gaps in our knowledge base exist. This review describes recent data on hearing loss in the VLBW population and explains the current level of understanding about the physiological basis underlying the auditory deficits in these patients. Although VLBW alone may not have a severe impact on hearing, it is commonly associated with multiple other risk factors that can alter hearing in a synergistic fashion. Therefore, the risk of hearing loss is substantially higher than in the general newborn population. Also, it is important to perform a more comprehensive audiometric evaluation than standard otoacoustic emission screening for infants who are in the neonatal intensive care unit in order not to miss hearing loss due to retrocochlear pathology. Furthermore, children with VLBW are also at increased risk of experiencing progressive or delayed-onset hearing loss, and thus should continue to have serial hearing evaluations after discharge from the neonatal intensive care unit.

The prevalence of congenital and early-onset hearing loss in Jordanian and Israeli infants

The objective of the study was to investigate the prevalence of congenital and early-onset hearing loss, and the influence of the known risk factors for hearing loss on infants in Jordan and Israel. Subjects were a total of nearly 17,000 infants from both countries, including infants with and without risk factors for hearing loss. The hearing screening protocol included distortion product otoacoustic emission, followed in case of repeated OAE referral or high risk (HR) infant by diagnostic auditory brainstem responses. The results indicate that the prevalence and severity of hearing loss amongst Jordanian infants (1.37%) is remarkably higher as compared to the Israeli infants (0.48%). The overall prevalence of bilateral SNHL was seven times more in the Jordanian infants, 18 times in non-risk, and three times in the HR infants relative to the Israeli infants. Risk factors including family history, hyperbilirubinemia, bacterial meningitis, and associated syndromes were more prevalent amongst Jordanian infants. This unique study underscores the importance of sharing and exchanging information to create empirical data to guide health-care providers in adapting protocols to the local constraints in developing countries.

Mumps meningoencephalitis effect on hearing

Sensorineural hearing loss is an important complication of mumps. Audiologic tests of 26 children with mumps meningoencephalitis, 25 uncomplicated mumps cases and 20 control cases were performed, and hearing level thresholds at speech and high frequencies were determined. The mean hearing level thresholds in the mumps meningoencephalitis group were higher than those of mumps cases at frequencies from 6,000 to 18,000 Hz in the right ear and at 250 and from 4,000 to 18,000 Hz in the left ear (P < 0.05). Mumps meningoencephalitis cases had higher mean hearing thresholds than did control groups at all frequencies other than 125 and 250 Hz in the right ear and 10,000 Hz in the left ear. The mean hearing thresholds of mumps cases were higher than those of control group at frequencies of 1,000 and 4,000 Hz in the right ear and 1,000 and 10,000 Hz in the left ear (P < 0.05). These results show that mumps meningoencephalitis causes a higher risk of hearing loss than does mumps.

Six year effectiveness of a population based two tier infant hearing screening programme

AIMS

To determine whether a two tier universal infant hearing screening programme (population based risk factor ascertainment and universal distraction testing) lowered median age of diagnosis of bilateral congenital hearing impairment (CHI) >40 dB HL in Victoria, Australia.

METHODS

Comparison of whole population birth cohorts pre and post introduction of the Victorian Infant Hearing Screening Program (VIHSP). All babies surviving the neonatal period born in Victoria in 1989 (pre-VIHSP) and 1993 (post-VIHSP) were studied. (1) Pre-1992: distraction test at 7-9 months. (2) Post-1992: infants with risk factors for CHI referred for auditory brain stem evoked response (ABR) assessment; all others screened by modified distraction test at 7-9 months.

RESULTS

Of the 1989 cohort (n = 63 454), 1.65/1000 were fitted with hearing aids for CHI by end 1995, compared with 2.09/1000 of the 1993 cohort (n = 64 116) by end 1999. Of these, 79 cases from the 1989 cohort (1.24/1000) and 72 cases from the 1993 cohort (1.12/1000) had CHI >40 dB HL. Median age at diagnosis of CHI >40 dB HL for the 1989 birth cohort was 20.3 months, and for the 1993 cohort was 14.2 months. Median age at diagnosis fell significantly for severe CHI but not for moderate or profound CHI. Significantly more babies with CHI >40 dB HL were diagnosed by 6 months of age in 1993 than in 1989 (21.7% v 6.3%). Compared to the six years pre-VIHSP, numbers aided by six months were consistently higher in the six years post-VIHSP (1.05 per 100 000 births versus 13.4 per 100 000 births per year).

CONCLUSIONS

VIHSP resulted in very early diagnosis for more infants and lowered median age of diagnosis of severe CHI. However, overall results were disappointing.

Incidence of hearing loss among children presented with speech-language delay

Infants' first attempts to communicate with their environment begin shortly after birth. However, real words appear by age of 12-15 months. Any delay in expressing their needs verbally beyond this age is defined as speech delay and may be associated with a variety of pathological conditions. The aim of this study is to investigate the incidence of hearing impairment in those children presented with speech delay. Ninety-one speech-delayed children were audiologically assessed between March 1993 and March 1995. In 25 out of 91 children (27.4%) a moderate to severe hearing loss was detected, either sensorineural or conductive. The increased incidence of hearing impairment found in this group mandates a thorough hearing evaluation for any case of speech-language delay.

Hearing loss in speech-language delayed children

An infant begins to communicate with his/her environment from the first months of life. However, true words do not appear until the age of 12-15 months, following a rather predictable sequence. Delay or failure of normal language development is not a rare situation in childhood and may be due to a variety of reasons. Among these, hearing undoubtedly plays a leading part in the language acquisition process. The purpose of this study was to assess the percentage of hearing-impaired children in a group of phenotypically healthy children presenting with speech-language delay. Between March 1993 and March 1999, 726 speech-language delayed children were examined in our department. In 72 of them, various diseases or syndromes had already been diagnosed and so they were excluded from the study. The remaining 654 apparently healthy children entered the study and underwent a thorough audiological assessment for determination of their hearing thresholds. Eighty-seven children (13.3%) showed various degrees of hearing loss. Most of them (55 children, 8.4%) suffered from sensorineural hearing impairment, while in 32 children (4.9%) a conductive hearing loss was discovered. The increased prevalence of hearing impairment found in our population mandates a thorough hearing evaluation for every case of speech-language delay, even for those children who show no evidence of other handicaps. This will help in the early diagnosis of hearing loss, allowing proper management to be instituted as early as possible.

Identification of neonatal hearing impairment: characteristics of infants in the neonatal intensive care unit and well-baby nursery

OBJECTIVE

The objective of this study was to describe the demographic data, medical status, and incidence of risk factors for hearing impairment in the neonatal intensive care unit (NICU) and well-baby populations in a multicenter prospective study designed to assess neonatal hearing impairment and to evaluate factors that might affect neonatal hearing test performance.

DESIGN

This was a prospective multicenter study funded by the National Institutes of Health-National Institute on Deafness and Other Communication Disorders to evaluate the effectiveness of auditory brain stem response, transient evoked otoacoustic emissions, and distortion product otoacoustic emissions for newborn hearing screening. Research staff at each site obtained informed consent and detailed demographic and medical data, including information on established risk factors for hearing loss on 4478 high-risk infants cared for in the NICU, 2348 infants from the well-baby nurseries with no risk factor, and 353 infants from the well-baby nurseries with risk factors. For follow-up purposes the sample was divided further to include a subgroup called selects. Selects were either infants from the well-baby nursery who had an established risk factor for hearing impairment (N = 353) or did not pass the neonatal hearing screen protocol (N = 80). In this study, we focus on the distribution of infants by nursery and risk factors only. Particular effort was made to enroll infants with risk factors for hearing loss in both the NICU and well-baby nurseries. Descriptive analyses are used to describe characteristics of this sample.

RESULTS

All 10 of the risk factors established by the Joint Committee on Infant Hearing in 1994 were identified in the NICU population. The four most common were ototoxic medications (44.4%), very low birth weight (17.8%), assisted ventilation > 5 days (16.4%), and low Apgar scores at 1 or 5 min (13.9%). In contrast, only six risk factors were present in the well-baby nurseries: family history (6.6%), craniofacial abnormalities (3.4%), low Apgar scores (2.8%), syndromes (0.5%), ototoxic medications (0.2%), and congenital infection (0.1%).

CONCLUSION

These descriptive risk factor data reflect both the newborn populations at the study sites and the bias for enrolling infants at risk for hearing loss. The high-risk NICU sample reflects the characteristics typically found in graduates of the NICU. The data summarized in this study will be used to assess the relationships between risk factor and hearing test outcome.

Relative and attributable risks for moderate to profound bilateral sensorineural hearing impairment associated with lower birth weight in children 3 to 10 years old

OBJECTIVE

To determine the prevalence, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment in relation to lower birth weight among children born in the 1980s and living in the metropolitan Atlanta area from 1991 through 1993.

METHODS

We used the population-based, active case ascertainment Metropolitan Atlanta Developmental Disabilities Surveillance Program that conducts surveillance in the five-county metropolitan Atlanta area. Hearing impairment was defined as a bilateral, pure-tone hearing loss at frequencies of 500, 1000, and 2000 Hz averaging 40 dBs or more, unaided, in the better ear. Case children, 3 to 10 years of age, with sensorineural loss of presumed congenital origin were included in these analyses (n = 172). Prevalence rates and relative risks were computed for various birth weight categories by hearing level, sex, race, the presence or absence of coexisting developmental disabilities, and gestational age. Attributable fractions were calculated for low birth weight and very low birth weight children by race.

RESULTS

The overall prevalence rate of presumed congenital bilateral sensorineural hearing impairment was 5.3 cases per 10 000 3-year survivors. The prevalence was 4.1 per 10 000 among children weighing >/=4000 g, 3.7 per 10 000 among those weighing 3000 to 3999 g, 6.6 per 10 000 among those 2500 to 2999 g, 12.7 per 10 000 among those 1500 to 2499 g, and 51.0 per 10 000 among those <1500 g. There was virtually no difference in birth weight-specific rates of hearing impairment across three hearing levels. The presence of coexisting developmental disabilities was associated with a much stronger inverse trend with birth weight. Black children weighing <2500 g had much higher rates of hearing impairment than comparable white children. The overall percentage of moderate to profound congenital bilateral sensorineural hearing loss in the entire study population that was attributable to children weighing <2500 g or <1500 g was estimated to be 18.9% and 9.4%, respectively. Prematurity did not alter the magnitude of risk among children weighing <2500 g.

CONCLUSIONS

The results presented here provide recent estimates of the rates, relative risks, and attributable fractions for congenital bilateral sensorineural hearing impairment by birth weight among children in the United States. The elevated relative risks among children weighing 2500 to 2999 g and 1500 to 2499 g may have implications for future newborn hearing screening criteria.

Otoacoustic emission-based hearing screening of a Greek NICU population

The pressing need for early identification of hearing-disabled children has led to the development of several neonatal hearing screening programmes world-wide. Today otoacoustic emissions represent a widely used methodology for identification of neonatal hearing impairment. The purpose of the present study is to determine the sensitivity and specificity of click-evoked otoacoustic emissions (cEOAEs) in a Greek NICU population and compare the cEOAE data to the final hearing status of these children. A total of 438 ears of 223 neonates at high risk for hearing impairment were tested with both brainstem response audiometry (ABR) and cEOAEs. In 107 neonates the final hearing status was determined by using behavioural and playtone audiometry, at an age greater than 2 1/2 years. The sensitivity and specificity of the cEOAEs were found to be 90 and 92.4% when compared to ABR results and 90.9 and 91.1% when compared to the children's hearing status, respectively. Click-EOAEs have been proved to be highly effective in determining whether or not hearing impairment really exists. Since conventional ABR does not meet the requirements for large scale screening programmes, the cEOAEs represent a reliable alternative.

The Rhode Island Hearing Assessment Program: experience with statewide hearing screening (1993-1996)

OBJECTIVE

The objective of this study was to evaluate key outcomes of a universal hearing screen/rescreen program for all births with transient evoked otoacoustic emissions in all 8 maternity hospitals in the state of Rhode Island over a 4-year period.

STUDY DESIGN

This was a retrospective analysis of the hearing screen/rescreen refer data collected prospectively for 53,121 survivors born in Rhode Island between January 1, 1993, and December 31, 1996. Primary outcomes included the first-stage refer rates, rescreen compliance, diagnostic referral rates, identification rates, and the age of amplification.

RESULTS

During this 4-year time period 11 infants were identified with permanent hearing loss, resulting in an impairment rate of 2 per 1000. The mean age of hearing loss confirmation decreased from 8.7 months to 3.5 months, and the age at amplification declined from 13.3 months to 5.7 months.

CONCLUSION

We conclude that time and experience are important factors in the development and refinement of a universal hearing screen program. Hearing screen outcome data collected over a 4-year period in Rhode Island reveal a steady improvement in the percent of infants completing the 2-stage screen process, the stage 1 and stage 2 refer rates, compliance with rescreen and diagnostic testing, and significant improvement in the age of identification and age of amplification.

Hearing loss at the age of 5 years of children born preterm--a matter of definition

The effect of three common hearing impairment criteria on the prevalence of hearing loss was evaluated in 58 prospectively followed-up 5-year-old children born preterm at < or = 32 weeks of gestation. Audiological assessment was done as part of an extensive neurodevelopmental evaluation at the age of 5 years. With the criterion based on the classification of the World Health Organization (average threshold hearing level > 25 dB at frequencies of 0.5, 1 and 2 kHz, classified according to the less impaired side) there were two preterm children with mild hearing impairment. With Clark's criterion (unilateral average threshold hearing level > 15 dB at frequencies of 0.5, 1 and 2 kHz) eight children had slight hearing impairment; seven of these had conductive hearing problems. With the criterion of a single frequency-specific deficit > 15 dB for 0.25-4 kHz the number of hearing-impaired children was 28 out of 54 (51.9%), most of whom had conductive or unspecified hearing deficits. Moreover, of the four multiply handicapped, retarded children whose pure tone thresholds were not assessed monaurally, three would belong to the hearing-impaired group according to Clark's criterion and four according to the frequency-specific criterion.

At-risk populations for hearing impairment in infants and young children

The epidemiologic patterns of childhood hearing loss are ill-defined. Patterns found in prospective observations of newborns in intensive care nurseries are quite different from the patterns apparent in retrospective studies of hearing-impaired children. High-risk registers, at least those prior to the 1990 reformulation, missed about half of children subsequently identified as having hearing loss. Items comprising high-risk registers carry unequal weight. Children with sensorineural hearing loss have a disproportionately increased occurrence of otitis media, with its conductive hearing loss. Sensorineural hearing loss can be progressive. Case-control studies of children with hearing loss are needed. Efforts for the early diagnosis of hearing loss in children must take into practical consideration the uncertainties of available epidemiologic data, and the clinical nuances.

Hearing loss in very preterm and very low birthweight infants at the age of 5 years in a nationwide cohort

In a geographically defined population of very preterm and very low birthweight infants (gestational age < 32 weeks and/or birthweight < 1500 g) hearing was evaluated in 890 children by pure-tone audiometry at the age of 5 years. Hearing loss was conductive/unspecified in 123 (13.8%) and sensorineural in 13 (1.5%) children. The prevalence of sensorineural hearing loss was 15 times as high as in 5-7 year old children in the Dutch population at large. The sensorineural hearing loss prevalence in very low birthweight and extremely low birthweight infants was similar. On account of communication disorders 10 (1.1%) children were classified as disabled and 6 (0.7%) as handicapped, following the definitions of the International Classification of Impairments, Disabilities, and Handicaps of the World Health Organisation. Children with conductive hearing loss had a higher risk of impairments, disabilities and handicaps of language and speech development, than children with normal hearing, the difference being statistically significant. The same holds for children with sensorineural hearing loss; moreover they had a significantly higher risk of impairments, disabilities and handicaps of mental development. Overall comparison of children with and without sensorineural hearing loss proved that the children with sensorineural hearing loss had a significantly less favourable outcome, based on 15 perinatal factors simultaneously. The age at which sensorineural hearing loss in very preterm and/or very low birthweight infants is detected has to be improved.