The effectiveness of the promotion of newborn hearing screening in Taiwan

Objective

Hearing is a critical ability for the development of a child's speech and language. Many studies in different countries have shown the universal newborn hearing screening and early intervention has greatly reduced the negative impact caused by congenital hearing loss. The first universal newborn hearing screening program in Taiwan took place in MacKay Memorial Hospital in 1998 and was subsequently endorsed by the government. The incidence of bilateral congenital hearing impairment in Taiwan is approximately 2.6 per 1000 live birth. The aim of this paper is to analyze the age of diagnosis, hearing aid fitting, and intervention of congenitally hearing impaired children with and without hearing screening after public awareness and government endorsement of newborn hearing screening.

Materials and methods

There were 263 hearing impaired children participated in this study, receiving their auditory habilitation therapy at Children's Hearing Foundation from 2006 to 2010. 114 of those children went through newborn hearing screening and 149 without it. The age of diagnosis, hearing aid fitting, and auditory intervention were compared between these two groups. The age of diagnosis and intervention of congenitally hearing impaired children among different years were analyzed too.

Results

The average age of diagnosis was 8.7 months, the age of hearing aid fitting was 12.4 months and age of auditory intervention was 18.8 months for the group of hearing impaired children with newborn hearing screening. For hearing impaired children without newborn screening, their average age of diagnosis was 27.5 months; age of hearing aid fitting was 31.3 months and age of auditory intervention was 40.5 months. There were significant differences in the age of diagnosis, hearing aid fitting and auditory intervention between congenitally hearing impaired children with and without hearing screening.

Conclusions

This research indicates that newborn hearing screening facilitates early identification, diagnosis and intervention of congenitally hearing impaired children in Taiwan. The age of identification, diagnosis and intervention of congenital hearing impaired children has also been reduced gradually over the years after government endorsement of newborn hearing screening in Taiwan.     

The economics of screening infants at risk of hearing impairment: an international analysis

Objective

Hearing impairment in children across the world constitutes a particularly serious obstacle to their optimal development and education, including language acquisition. Around 0.5-6 in every 1000 neonates and infants have congenital or early childhood onset sensorineural deafness or severe-to-profound hearing impairment, with significant consequences. Therefore, early detection is a vitally important element in providing appropriate support for deaf and hearing-impaired babies that will help them enjoy equal opportunities in society alongside all other children. This analysis estimates the costs and effectiveness of various interventions to screen infants at risk of hearing impairment.

Methods

The economic analysis used a decision tree approach to determine the cost-effectiveness of newborn hearing screening strategies. Two unique models were built to capture different strategic screening decisions. Firstly, the cost-effectiveness of universal newborn hearing screening (UNHS) was compared to selective screening of newborns with risk factors. Secondly, the cost-effectiveness of providing a one-stage screening process vs. a two-stage screening process was investigated.

Results

Two countries, the United Kingdom and India, were used as case studies to illustrate the likely cost outcomes associated with the various strategies to diagnose hearing loss in infants. In the UK, the universal strategy incurs a further cost of approximately £2.3 million but detected an extra 63 cases. An incremental cost per case detected of £36,181 was estimated. The estimated economic burden was substantially higher in India when adopting a universal strategy due to the higher baseline prevalence of hearing loss. The one-stage screening strategy accumulated an additional 13,480 and 13,432 extra cases of false-positives, in the UK and India respectively when compared to a two-stage screening strategy. This represented increased costs by approximately £1.3 million and INR 34.6 million.

Conclusions

The cost-effectiveness of a screening intervention was largely dependent upon two key factors. As would be expected, the cost (per patient) of the intervention drives the model substantially, with higher costs leading to higher cost-effectiveness ratios. Likewise, the baseline prevalence (risk) of hearing impairment also affected the results. In scenarios where the baseline risk was low, the intervention was less likely to be cost-effective compared to when the baseline risk was high.     

An initial overestimation of sensorineural hearing loss in NICU infants after failure on neonatal hearing screening

Objective

Infants admitted to neonatal intensive care units have a higher incidence of significant congenital hearing loss. We classified audiologic diagnoses and follow-up in infants who had been admitted to our neonatal intensive care unit.

Methods

We included all infants admitted to the neonatal intensive care unit at Sophia Children's Hospital between 2004 and 2009 who had been referred for auditory brainstem response measurement after failing neonatal hearing screening with automated auditory brainstem response. We retrospectively analyzed the results of auditory brainstem response measurement.

Results

Between 2004 and 2009 3316 infants admitted to our neonatal intensive care unit had neonatal hearing screening. 103 infants failed neonatal hearing screening: 46 girls and 57 boys. After first auditory brainstem response measurement we found 18% had normal hearing or a minimal hearing loss. The remainder had a type of hearing loss, distributed as follows: 15% conductive, 32% symmetric sensorineural, 14% asymmetric sensorineural, and 21% absent auditory brainstem responses. Repeated auditory brainstem response measurement showed a shift in hearing outcome. The main difference was an improvement from symmetric sensorineural hearing loss to normal hearing. However, in a small percentage of children, the hearing deteriorated.

Conclusions

As many as 58% of infants in this high-risk population who failed the neonatal hearing screening were diagnosed with sensorineural hearing loss or absent auditory brainstem responses. An initial overestimation of sensorineural hearing loss of about 10% was seen at first auditory brainstem response measurement. This may be partially explained by a conductive component that has resolved. Finally, in a small percentage of children the hearing deteriorated.     

Neonatal hearing screening in Benin City

Objective

Congenital hearing loss is a major health care problem that tends to retard the developmental milestones of children. It takes early detection and intervention to avoid a permanent loss in acquisition of speech and cognitive functions. Hence, the importance of hearing screening in all newborns especially in the developing world for accurate statistics and early intervention. Therefore, this work was aimed at detecting the crude prevalence of congenital hearing loss among the newborns in Benin City.

Methodology

Consecutive neonates at designated immunization centers in Benin City metropolis were screened for hearing loss via the detection and analysis of distortion product otoacoustic emissions from both ears. The handheld otoacoustic machine model MAICO 8172 was employed and the outcome results presented in tables. Statistical analysis was performed using SPSS 11.

Results

A total of 400 neonates (218 males and 182 females) were screened for the presence of otoacoustic emission in both ears. Ninety neonates (22.5%) p < 0.05 were referred. Bilateral hearing loss was seen in 26 (6.5%) whereas 64 (16%) had unilateral loss.

Conclusions

The screening tests suggest a high crude prevalence (6.5%) of bilateral neonatal hearing impairment in Benin City necessitating confirmation and intervention. The study fortifies the need for hearing screening among all new born in developing countries.     

Findings from multidisciplinary evaluation of children with permanent hearing loss

Objectives

To describe clinical findings from a multidisciplinary program for children with permanent hearing loss (PHL).

Methods

Retrospective chart review at a tertiary care children's hospital. Patients: Two hundred patients charts were selected from the population of 260 children with permanent hearing loss presenting between July 2005 and December 2006. Main outcome measures: PHL etiology; radiographic findings; clinical findings by genetics, ophthalmology, developmental pediatrics, speech pathology, and aural rehabilitation.

Results

Etiology of hearing loss was determined in 60% of subjects. Genetic causes of hearing loss were identified or presumed (positive history of first degree relative with hearing loss) in 27% of the children. Structural ear anomalies were found in 20% of children. Among the 36% of children with CNS imaging, abnormal findings were noted in 32%. There were a high rate of ophthalmological findings (53%) among children seen by ophthalmology (n = 105). Neurodevelopmental evaluations were completed in 58% of subjects and clinically significant findings were noted in 68%. Of the 61% of children who receiving received speech/language evaluations, 77% required intervention. Over half of the 40% of subjects who had an aural rehabilitation evaluation needed therapy. There were not significant differences in rates of findings for children with mild or unilateral hearing loss as compared to children with more severe degrees of hearing loss.

Conclusions

Interdisciplinary medical evaluation of children with PHL allows for the identification and treatment of clinically significant ophthalmologic, neurodevelopmental, genetic, and speech/language disorders. A high rate of CNS and temporal bone abnormalities were identified. These findings provide an understanding of the importance of considering thorough medical and developmental evaluations among children who are deaf/hard of hearing.     

Place of birth and characteristics of infants with congenital and early-onset hearing loss in a developing country

Objective

To determine the characteristics of infants with sensorineural hearing loss (SNHL) and the relationship with place of birth.

Methods

Subjects were drawn from hospital-based and community-based universal infant hearing screening programs concurrently conducted from May 2005 to April 2008 in Lagos, Nigeria. Maternal and infant characteristics of children born in hospitals and detected with SNHL were compared with those born outside hospitals. Each program consisted of a first-stage screening with transient-evoked otoacoustic emissions (TEOAE) followed by second-stage automated auditory brainstem response (AABR). Hearing status was confirmed by diagnostic auditory brainstem response, tympanometry and visual response audiometry.

Results

A total of 4718 infants were screened under the hospital-based program out of which 12 (0.3%) infants were confirmed with SNHL whereas 71 (1.0%) of the 7179 infants screened under the community-based program were confirmed with SNHL. Of all infants with SNHL 39 (47.0%) were born in hospitals suggesting that 27 (38.0%) of infants under the community-based program were born in hospitals. Prevalence of SNHL ranged from 4.0 per 1000 among infants born in government hospitals to 23 per 1000 among those born in family homes. Mothers of those born outside hospitals were significantly likely to belong to the Yoruba tribe (p < 0.001), use herbal medications in pregnancy (p < 0.001), deliver vaginally (p = 0.004) but without skilled attendants at delivery (p < 0.001). There were no significant differences among the infants themselves except that those born outside hospitals were significantly likely to be detected in the first 3 months of life compared to those born in hospitals (p < 0.001).

Conclusions

A significant proportion of infants with SNHL in many developing countries are likely to be born outside hospitals thus underscoring the need for community-oriented UNHS to facilitate early detection and intervention. Conventional risk factors for SNHL are unlikely to discriminate across places of birth. Pediatricians and otolaryngologists should consider a more active role in fostering community-oriented delivery of primary ear care services in this and similar settings in the developing world.     

Newborn hearing screening on infants at risk

Objectives

This article presents the results of newborn hearing screenings on infants at risk of hearing impairment at the French University Hospital of Besançon from 2001 to 2007.

Materials and methods

All newborns at risk of hearing impairment were tested according to the method recommended by the Joint Committee on Infant Hearing (JCIH): a two-step automated oto-acoustic emissions (AOAE) program, completed by an auditory brainstem response (ABR) for the positive diagnosis of hearing impairment. The screening started with AOAE on the third day of life, at the earliest. If one or both ears did not have AOAE, the infant was re-tested at which time, should the AOAE again be positive, ABR was performed. When the ABR threshold was 40 dB or more, the infant was referred to an audiologist specialized in infant deafness for diagnosis confirmation and management.

Results

Over the period, 1461 infants were screened, among whom 4.55% were diagnosed as deaf or hard of hearing. Nearly 10% of the infants were lost to follow up. Forty-six children had a sensorineural hearing impairment, of which 34 were bilateral and were managed before the age of 6 months. The risk factors for sensorineural hearing loss were (in order of statistical significance): severe birth asphyxia; neurological disorder; syndromes known to be associated with hearing loss; TORCH (toxoplasmosis, rubella, cytomegalovirus, herpes) infections; family history of deafness; age at the time of screening; and the association of 2 or more risk factors. However, birth weight inferior to 1500 g and premature birth before the 34th week of pregnancy did not show a statistically significant influence on sensorineural hearing loss. Craniofacial anomalies (mostly cleft palate and ear aplasia) were a significant factor for conductive hearing loss.

Conclusion

Our selected hearing screening on infants at risk allowed 60 deaf children access to early management. However, too many children were lost to follow up; which revealed that better information regarding risk of hearing loss must be provided to parents and paramedics and universal newborn screening needs to be performed. The most important result of this study is that in a population of hearing impaired children, with an impairment incidence close to what is commonly reported, the association of several risk factors proves to be a significant additional risk factor for hearing impairment.     

Etiological diagnosis in the hearing impaired newborn: proposal of a flow chart

Objective

Most industrialized countries have introduced some form of universal newborn hearing screening program. Both identification and rehabilitation of hearing loss in newborns have evolved to an acceptable standard and the need for a standardized etiological protocol is emerging.

Methods

Extensive literature search to determine which investigations can help identifying the cause of congenital hearing loss and how to limit extensive testing in these children by taking into account the most prevalent causes.

Findings

A stepwise approach to detect the cause of hearing loss in children with congenital sensorineural hearing loss was developed.

Conclusion

In general it is advised to first rule out Cx26/Cx30 and infectious causes (cytomegalovirus and, if indicated, toxoplasmosis and rubella), and to preserve more extensive investigations for those children in whom these causes do not explain the hearing loss.     

Prevalence of the c.35delG and p.W24X mutations in the GJB2 gene in patients with nonsyndromic hearing loss from North-West Romania

Objective

In Central and South-Eastern European countries, the most frequent mutation types responsible for congenital nonsyndromic sensorineural hearing loss (NSHL) are c.35delG and p.W24X (15-55.8% and 2.5-4.3%, respectively). The aim of the study was to determine for the first time in Romania the prevalence of c.35delG and p.W24X mutations in patients with NSHL.

Material

75 unrelated children with NSHL from Transylvania (North-West Romania).

Methods

a. Audiological examination (otoscopy, tympanogram, acoustic otoemission and tonal audiogram or auditory evoked potentials); b. detection of the c.35delG (semi-nested-PCR, RFLP and ARMS-PCR analysis) and p.W24X (ARMS-PCR analysis) mutations.

Results

Audiological examination allowed the diagnosis of hearing loss of various degrees: moderate in 8 patients (10.7%), severe in 14 cases (18.7%), profound in 53 patients (70.6%). The number of reported mutation cases as against the number of alleles indicates a 33.3% frequency rate for c.35delG mutation and respectively 5.3% for p.W24X mutation. All 22 patients with 35delG/c.35delG genotype (19 patients), c.35delG/p.W24X genotype (2 patients) or p.W24X/p.W24X genotype (1 patient) presented profound/severe hearing loss.

Conclusion

Our study confirms that the frequency rate of the two mutations analyzed in patients with NSHL from North-West Romania is comparable to that seen in other Central and South-Eastern European countries. The homozygote or compound heterozygote states represent a major risk factor for profound or severe deafness. Audiological screening in newborns and genetic testing in confirmed congenital hypoacusis cases are compulsory for early therapeutic intervention (hearing prosthesis or cochlear implant) and genetic counselling.     

Newborn hearing screening and genetic testing in 8974 Brazilian neonates

Objective

An early diagnosis has been a priority in the audiological practice. Identifying hearing loss until 3 months old through Universal Newborn Hearing Screening and intervention before 6 months old, minimize the impact of auditory loss in the health and communication development of these children. However, in the clinical practice, despite the help of the risk indicators in the audiological and etiological diagnosis, the integrated services have come up against the challenge of determining the causes of auditory loss, bearing in mind that approximately 50% of the subjects who have congenital loss do not show risk factors in their clinical history. The current research aims introduce together etiologic and audiological diagnosis of newborns.

Methods

We eluted dried blood spots from paper and performed genetic testing for 35delG mutation in 8974 newborns that were also screened for transient otoacoustic emissions (TOAE). In addition, the A1555G and A827G mutations in the MTRNR1 mitochondrial gene were screened in all newborns.

Results

We have found 17 individuals who failed in TOAE. Among them, we detected 4 homozygous newborns for 35delG mutation and 3 individuals with A827G mutation in the MTRNR1 mitochondrial gene. The frequency of 35delG carriers was 0.94% [84/8974]. In all 17 individuals who failed in OAE no other mutation besides those mentioned above was found.

Conclusions

The results greatly contribute to the public health area indicating the etiologic diagnosis, allowing family counseling as well as the early rehabilitation treatment or surgical intervention. Over time that will help to reduce the costs of rehabilitation considerably.     

Newborn hearing screening in a developing country: Results of a pilot study in Abidjan, Côte d’ivoire

Objective

To investigate the feasibility of neonatal hearing impairment in newborn babies in Abidjan, Côte d’Ivoire.

Methods

It is a cross-sectional study in which all infants aged from 3 to 28 days, attending for Bacille Calmette-Guerin (BCG) immunization in primary care centers or hospitalized in neonatal intensive care units (NICU), between July 2007 and March 2008, were included. Screening followed a two-stage strategy with transient evoked otoacoustic emissions (TEOAE). Infants referred after the second-stage screening were scheduled for diagnostic evaluation by diagnostic auditory brainstem response (ABR). The variables analyzed were: screening coverage, referral rates; return rates for second-stage screening and diagnostic evaluation, incidence of permanent hearing loss and age at diagnosis.

Results

1306 newborns, of a total of 1495, were successfully screened, giving a screening coverage of 87.4%. The average age was 4.5 days (S.D.: 2.7), with 5.85 days (S.D.: 3.17) for the immunization group and 3.20 days (S.D.: 0.40) for the neonatal unit group. In total, 286 out of the 1306 infants (21.9%) were referred after the first-stage screening; out of which 193 (67.5%) return for the second stage. After the second-stage screening, 48 (16.8%) were scheduled for diagnostic evaluation (45 from NICU and 3 from primary care centers). The overall referral rate for diagnostic evaluation was 3.7% (48/1306). Only 18.75% of those referred (9/48) returned for evaluation, and seven of them (77.8%) were confirmed with hearing loss (2 from immunization group and 5 from neonatal unit group). The prevalence of permanent hearing loss in this screened population was 5.96 per 1000 (7/1174 babies who completed the screening) [95% I.C.: 5.62-6.30 per 1000]. The mean age at diagnosis was 22 weeks (S.D.: 8.3). The reasons for non-completed screening were, according to 62 mothers: no financial means, absence of hearing loss, fear of spouse reactions, lack of information about this test and deafness.

Conclusion

The incidence of permanent and early hearing impairment identified by this screening program was about 6 per 1000. Routine hearing screening of infants for the early detection of hearing loss is necessary in Côte d’Ivoire. It is possible to implement such a hearing screening, targeting all newborns, in primary health care centers and neonatal intensive care units.     

Qualitative analysis of parents’ experience with receiving the news of the detection of their child's hearing loss

Objective

Despite the fact that clinicians are responsible for delivering bad news, they have been shown to lack both confidence and skill in performing this basic task. The time immediately after the detection of childhood hearing loss is perceived as stressful. We conducted a qualitative study to assess parents’ experiences with receiving the bad news of the detection of their child's hearing loss.

Study design

Semi-structured interviews were conducted with families of children with hearing loss identified during early childhood.

Setting

A rehabilitation center treating pre-school children in the north of Israel.

Patients

14 families/parents of children diagnosed prior to the implementation of a universal screening program.

Main outcome measure

Parents’ perceptions of the manner in which the information regarding the detection of their child's hearing loss was given, and what their feelings were at the time.

Results

50% of parents expressed dissatisfaction with the process of the breaking of the bad news. ABR is perceived by parents and health professionals alike as the definitive moment of diagnosis. The emotions experienced by parents at the moment of the breaking of the bad news were predominantly shock and upset. The meaning of the news was perceived differently under different circumstances. Information given bluntly, without empathy, was a frequent complaint. Parents repeatedly stated the importance of the formulation of a plan for the future.

Conclusions

Qualitative enquiry provided valuable information. Effective strategies for the breaking of bad news should become an integral part of universal neonatal screening programs.     

Risk factors for elevation of ABR threshold in NICU-treated infants

Objective

Several risk factors for hearing impairment among infants treated in the neonatal intensive care unit (NICU) have been reported, but there have been few studies that show the correlation strength between the risk factors in NICU-treated infants and hearing impairment in childhood. The aim of this study was to clarify the relationship between risk factors in NICU-treated infants and a deteriolation of auditory brainstem response (ABR) threshold in their childhood.

Methods

One hundred one NICU-treated infants with ABR threshold of 50 dBnHL or more underwent 2nd ABR test at 20 months after delivery. Multiple regression analysis was performed with ABR threshold change as an objective variable and risk factors as explanatory variables.

Results

Two ABR tests of the 101 infants resulted in that 7 showed an elevation of ABR threshold by 20 dB, 70 showed a drop of ABR threshold by 20 dB, and 24 showed no significant change. Multiple regression analysis revealed that the factors contributing to the elevation of ABR threshold were congenital diaphragmatic hernia, severe respiratory disease, and a high C-reactive protein (CRP) level.

Conclusions

In the infants treated in NICU, an incidence of ABR threshold of 50 dBnHL or more was 9.0%, and 6.9% of the infants with the ABR threshold abnormality showed a significant elevation of ABR threshold in their childhood. Factors significantly related to an elevation of ABR threshold were a history of congenital diaphragmatic hernia, severe respiratory disease, and elevation of CRP. In infants with such factors, periodical examination of hearing is required.     

Characteristics of hearing impairment in Yemeni children with chronic suppurative otitis media: A case-control study

Background

Chronic suppurative otitis media (CSOM) is a serious disorder particularly in low resource settings. It can lead to disabling hearing impairment and sometimes life-threatening infective complications.

Objective

The aim of the present study was to describe the characteristics of hearing impairment associated with CSOM in Yemeni children.

Methods

A case-control study of 75 children with CSOM and 74 healthy controls. Hearing was assessed by behavioural testing and audiometry.

Results

Cases had lower academic performance than controls (OR 15.31, 95% CI 1.99-322.14, p < 0.001). Disabling hearing impairment >30 dB was present in 51.5% (right ear) and 66.7% (left ear) of children with CSOM.

Conclusion

Disabling hearing impairment was identified as a major health problem in these Yemeni children with CSOM. There is a need for investment to reduce the burden of CSOM and its complications in these communities. Greater attention to the chronic disabling effects of CSOM in children is required in poor communities and low resource settings.     

The audiological characteristics of a hereditary Y-linked hearing loss in a Chinese ethnic Tujia pedigree

Objective

To investigate audiometric characteristics of hearing loss in a large Chinese ethnic Tujia family and determine its hereditary type.

Methods

Total 76 live individuals were investigated in the notable 84 members of this family. The detailed audiometric evaluations were undertaken for the proband and his 47 family members. The degrees of sensorineural hearing impairment were defined as an air/bone gap <15 dB hearing loss averaged over 0.5, 1 and 2 kHz. The severity of hearing loss was established based on the hearing ability of the better ear, averaged over 0.5, 1, 2 and 4 kHz, and classified into four categories: mild, moderate, severe and profound.

Results

Nineteen patrilineal relatives of the 76 live members had hearing impairment. The age of onset ranged from 7 to 21 years old with the average of 13.2 years. The audiometric defect was described by auditory curves of a high frequency in 47% of the patients. Affected members in this family demonstrated a non-syndromic, late onset, bilateral, symmetrical, postlingual and sensorineural hearing loss.

Conclusions

The audiometric configuration in males of the pedigree is consistent with the hereditary Y-linked hearing loss. Thus we speculate that a putative gene on the Y chromosome could contribute to the cause of the disease.     

Auditory evoked magnetic fields in children with functional hearing loss

Objectives

Abnormal cortical responses in patients with functional hearing loss were evaluated by magnetoencephalography, which can better separate bihemispherical activity than electroencephalography.

Methods

Auditory evoked fields in response to 1 kHz or 2 kHz tone bursts at 80 dB sound pressure level were measured by a helmet-shaped magnetoencephalography system in 22 patients with functional hearing loss (18 females, mean age 13.2 years) as well as 5 control subjects under 10 years old. Waveform, latency, and equivalent current dipole of N100m responses were used to evaluate activity in the bilateral auditory cortices.

Results

Abnormal N100m of the contralateral response to the stimulated ear, either absence or delayed latency in comparison to normal adult subjects, was found in 6 of the 7 patients with functional hearing loss aged 9 years or younger, but in only 3 of the 15 patients aged 10 years or older. However, such abnormalities were also observed in younger control subjects.

Conclusion

Auditory evoked field may be applied to objectively evaluate cortical auditory function in patients with functional hearing loss, but the normal findings for young children have not yet been established.     

Prevalence and etiology of congenital or early acquired hearing impairment in Eastern Finland

Objective

The purpose of this study was to determine the prevalence and etiology of congenital or early acquired bilateral sensorineural hearing impairment (SNHI) in children born from 1988 to 2002 in the district of Kuopio University Hospital, Finland, and to compare the results with those from an earlier 14-year period in the same region and similar population.

Methods

The data were collected retrospectively from Hospital Records. The degree of hearing impairment was based on average air conduction threshold calculated over the frequencies 0.5, 1, 2 and 4 kHz in the better hearing ear. Hearing impairment was classified as mild (≥20-39 dB), moderate (40-69 dB), severe (70-95 dB) and profound (>95 dB).

Results

We identified 92 children with bilateral SNHI diagnosed before the age of 7 years. The overall prevalence and the prevalence for at least moderate SNHI was 2.1 per 1000 live births and 1.2 per 1000 live births, respectively. We found no differences in the prevalence of SNHI during both study periods. Etiology was genetic in 46%, acquired in 14% and unknown in 40%. Out of the genetic cases 74% were non-syndromic and 26% were syndromic. In comparison to the previous study there was a decline in the proportion of acquired SNHI and the proportion of genetic and unknown cause had increased. Six children in five families had homozygous 35delG mutation and six children in four families presented with a homozygous M34T mutation.

Conclusions

The prevalence of congenital or early acquired SNHI in the Kuopio University Hospital district area has not changed during a period of 29 years. Despite possibility to test the GBJ2 gene, the proportion of hearing impairment of unknown etiology remained high.     

Prevalence of auditory neuropathy (AN) among infants and young children with severe to profound hearing loss

Auditory neuropathy is a challenging disorder and needs special habilitative/rehabilitative approach. This study aimed to detect its prevalence among infants and young children with severe to profound hearing loss. 112 infants and young children with age ranged 6-32 months were examined and diagnosed as having severe to profound hearing loss and were referred for hearing aid fitting. Those infants were reassessed in our centers for detecting cases with auditory neuropathy. The study group was subjected to immittancemetry, behavioral observation audiometry, ABR and cochlear microphonics.

Results

15 patients were found to have auditory neuropathy according to our criteria for diagnosis.

Conclusions

The prevalence of AN in the study group was 13.4%. CM were recommended to be tested routinely during ABR assessment whenever abnormal results are obtained.