This study set out to provide further information on how high modulation/stimulus rates affect the auditory steady-state response (ASSR) amplitude for a 1000-Hz tone, and how this effect varies between individuals. Both sinusoidal amplitude modulated tones and tone pip stimuli were investigated.
Modulation/stimulus rates were 70, 80, and 90 Hz and the peak to peak stimulus levels were matched for the two different types of stimuli, at 90.5 dBSPLppe.
The study was carried out on fourteen normally-hearing adults (9 males and 5 females)
Overall the ASSR amplitude to the two types of stimuli was similar. In general there was an increasing response amplitude between rates of 70 and 90 Hz; The relationship between the amplitude of the response and the modulation /stimulus rate varied considerably between subjects.
Optimum stimulus rates based on group data may not give the best rate in a significant proportion of subjects. Currently tone pip ABR is the primary method used in assessing hearing in babies. Finding a way of avoiding suboptimal stimulus rates for '80-Hz' ASSR in babies will improve the likelihood of ASSR being seen as an alternative.
This study aimed to evaluate the test-retest reproducibility of the high frequency tympanometry (HFT) test measured in healthy infants. A total of 273 newborn babies (106 males and 147 females) were assessed twice (Test 1 and Test 2) on the same day, followed by two more assessments (Test 3 and Test 4) for 118 babies (48 males and 70 females) who returned six weeks later. Five HFT measures including the peak compensated static admittance and component compensated static admittance were assessed for test-retest reproducibility. The results showed no significant differences in mean values of the HFT results between the test and retest conditions for newborn (Test 1/ Test 2) and six-week-old babies (Test 3/ Test 4). High reproducibility for all HFT measures was found for both age groups, as judged by the high intra-correlation coefficients of between 0.75 and 0.95. Normal variations of the HFT measures were established using the 90% range of absolute test-retest difference. Changes in test-retest findings exceeding the 95th percentile values may be considered significant, indicating possible functional changes.
To evaluate the frequency of GJB2 mutations and their correlation with phenotype in Sicilian non-syndromic sensorineural hearing loss (NSHL) patients.
Sequencing of the coding region, basal promoter, exon 1, and donor splice site of the GJB2 gene; screening for the presence of the two common GJB6 deletions.
A cohort of 102 Sicilian NSHL patients.
Fifteen different mutations in GJB2 and seventeen different genotypes were detected. No GJB6 mutations were found. The hearing impairment was profound in the 64.72% of probands (mean PTA0.25-4 kHz of 88.82 ± 26.52 dB HL). A total of 81.37% of patients harboured at least one c.35delG allele; c.167delT and c.-23 + 1G> A were identified in 10.78% and the 9.8% of patients respectively; c.35delG homozygotes presented more severe hearing impairment (75.59% of profound hearing loss) and a higher mean PTA0.25-4 kHz (96.79 ± 21.11 dB HL) with respect to c.35delG/non-c.35delG and c.35delG/Wt patients (P < 0.05).
This work underlines the role of c.35delG, c.167delT and c.-23 + 1G> A as the most frequent causes of NSHL in Sicily. The c.35delG frequency found is similar to those reported in other populations of the Mediterranean area. The analysis of genetic and audiologic data confirmed a variability in the phenotype associated to a single genotype.
Rudner et al (37.
Rudner M., Foo C., Rönnberg J. & Lunner T. 2008. Phonological mismatch causes explicit cognitive processing when listening conditions are taxing Submitted manuscript.View all references) showed that when compression release settings are manipulated in the hearing instruments of Swedish habitual users, the resulting mismatch between the phonological form of the input speech signal and representations stored in long-term memory leads to greater engagement of explicit cognitive processing under taxing listening conditions. The mismatch effect is manifest in significant correlations between performance on cognitive tests and aided-speech-recognition performance in modulated noise and/or with fast compression release settings. This effect is predicted by the ELU model (Rönnberg et al, 2008). In order to test whether the mismatch effect can be generalized across languages, we examined two sets of aided speech recognition data collected from a Danish population where two cognitive tests, reading span and letter monitoring, had been administered. A reanalysis of all three datasets, including 102 participants, demonstrated the mismatch effect. These findings suggest that the effect of phonological mismatch, as predicted by the ELU model (35.
Rönnberg J., Rudner M., Foo C. & Lunner T. This issue. Cognition counts: A working memory system for ease of language understanding Int J Audiol, 47, 82.View all references et al, this issue) and tapped by the reading span test, is a stable phenomenon across these two Scandinavian languages.
To determine the equivalent threshold sound pressure levels (ETSPL) for a commercially available distortion product otoacoustic emission (DPOAE) probe, and to study the impact of probe fitting and eartip size on the calibration.
Twenty-eight otologically normal test subjects participated in the ETSPL determination for the Etymotic Research ER-10C probe.
ETSPLs were determined up to 16 kHz and were compared to the reference hearing thresholds associated with the ER-3A insert earphone. Both 'regular' and 'baby' foam eartips were used.
At most frequencies, no significant threshold differences were observed between the insert earphone and the DPOAE probe. However, at 1 kHz and 4 kHz, the mean thresholds for the insert earphone were generally lower than those for the DPOAE probe, suggesting systematic differences at those frequencies. Repeated calibration runs resulted in deviations of about 0.6 dB. Similar deviations were noticed when using foam eartips of different sizes up to 10 kHz.
Knowing the reference thresholds for DPOAE probes enables measurements of (subjective) hearing thresholds and (objective) otoacoustic emissions using the same probe. Probe fitting and eartip size had negligible effect on the determination of ETSPLs. The obtained data may be proposed for inclusion in future audiometry standards.
This study aimed to assess prevalence and risk factors for mild/high-frequency bilateral sensorineural hearing loss within a UK population of children at age 11 years.
Prospective birth cohort study.
Repeat hearing thresholds were measured in 5032 children, as part of the Avon Longitudinal Study of Parents and Children (ALSPAC) at age 7, 9, and 11 years. Pregnancy, birth, and early medical history were obtained prospectively through parental questionnaires and medical records.
Twenty children had mild and seven had high-frequency bilateral sensorineural hearing loss, giving a combined prevalence of 0.5% (95% CI 0.4-0.8%). These children were more likely than the rest of the study sample to have been admitted to hospital at 6-18 months (OR 2.7, 95% CI 1.00-7.30). Parents of these children were more likely to have suspected a hearing problem when the children were 3 years old (OR 2.4, 95% CI 1.05-5.60).
This is the first UK prospective cohort study to investigate the prevalence of mild and high-frequency hearing loss. This study, which has the advantage of a large sample size and repeat hearing measures over a four year period, reports lower prevalence values than US cross-sectional studies.
Detailed information on the hearing threshold levels (HTLs) of young Australians was gathered as part of a large-scale study of the relationship between HTL and leisure-noise exposure in young Australians.
HTL data for the study population (18-35 year olds) was carefully collected, as well as otoscopy, tympanometry, contra-lateral acoustic reflexes, and otoacoustic emissions (transient and distortion product), together with a comprehensive hearing health history - both past and present.
The sample cohort consisted of 1407 individuals, females and males.
Prior to analysis, HTL data were filtered according to both a 'Low' and 'High' set of exclusion criteria. The results obtained for both high-screen and low-screen datasets were around +5 dB above the traditionally accepted values of audiometric zero. This is consistent with previous published reports.
Comparison with 'ISO 7029 Acoustics: Statistical distribution of hearing thresholds as a function of age' indicated that threshold values for this dataset have a similar distribution to those of the Standard. This data provides a suitable reference HTL ('normative') database for young Australians.
Although measurement of the detection limits of the 80 Hz auditory steady-state response (ASSR) has proven to be a reasonably reliable tool in estimating hearing sensitivity in the mid-conventional audiometric frequencies (e.g. 1000 and 2000 Hz), results in the literature suggest potentially diminishing performance at 500 Hz and above 4000 Hz. The primary goal of this work was to examine the accuracy of threshold estimation via ASSR measurement for carriers more toward the audiometric extremes. At the same time, different stimulus and recording protocols than those commonly employed in ASSR testing were examined. Using a two-channel recording system, ASSRs were obtained from 15 normal-hearing young adults for an amplitude-modulated carrier of 250 Hz and repeated tone bursts of 10,000-16,000 Hz, gated using a Blackman window. Results attest to the ability to record ASSRs to a wide range of carrier frequencies but also suggest that accuracy of threshold estimation suffers toward the audiometric extremes. Feasibility of ASSR-based high-frequency audiometry is demonstrated in principle, but it is not clear that this method will permit adequate sensitivity and accuracy to support such applications as ototoxicity monitoring.
Objective and design:
This retrospective cohort study aimed to describe the differential effect of noise exposure and age-related hearing loss in a large sample of gold miners in South Africa.
Audiological data of 40 123 South African mine workers were investigated. Data of a non-noise-exposed control group (n = 6162) and group exposed to underground noise (≥ 85 dB A (TWA) (n = 33 961) were included. Within these two larger noise-exposed groups two homogenous exposure groups (HEG) were also selected for analyses, namely the driller group (n = 4399) and the administration group (administrative workers) (n = 2211). Participants were categorized in terms of noise exposure, age, and race.
Significantly different thresholds (worse for underground noise group) with respect to the median for all frequencies after adjusting for age was evident between the noise-exposed and control groups (ANCOVA). The largest differences in hearing thresholds between the noise-exposed and control groups were observed at 3 and 4 kHz in the age group 36 to 45 years. Administration and driller group differed significantly (driller group worse results) with respect to the mean LFA512 and HFA346 after adjusting for age (ANCOVA). Black males had significantly better high-frequency hearing compared with white male counterparts but significantly worse low-frequency hearing.
Age was the most important influence on hearing thresholds for the noise and control groups. Race was shown to be a very significant factor determining susceptibility to NIHL and ARHL.
Hearing threshold sound pressure levels were measured for the Sennheiser HDA 280 audiometric earphone. Hearing thresholds were measured for 25 normal-hearing test subjects at the 11 audiometric test frequencies from 125 Hz to 8000 Hz. Sennheiser HDA 280 is a supra-aural earphone that may be seen as a substitute for the classical Telephonics TDH 39. The results are given as the equivalent threshold sound pressure level (ETSPL) measured in an acoustic coupler specified in IEC 60318-3. The results are in good agreement with an independent investigation from PTB, Braunschweig, Germany. From acoustic laboratory measurements ETSPL values are calculated for the ear simulator specified in IEC 60318-1. Fitting of earphone and coupler is discussed. The data may be used for a future update of the RETSPL standard for supra-aural audiometric earphones, ISO 389-1.
The main results in Poulsen & Oakley (2009) are given as the equivalent threshold sound pressure level, ETSPL, measured in an acoustic coupler specified in IEC 60318-3. These results are all correct. The ETSPL values for the ear simulator specified in IEC 60318-1 were calculated from acoustic laboratory measurements and unfortunately a simple sign error has been found that changes two of the columns in Table 3 of Poulsen & Oakley (2009).
To explore the molecular genetic characterization of two Chinese families with aminoglycoside-induced and non-syndromic hearing loss (NSHL).
Clinical evaluations, sequence analysis of mitochondrial DNA (mtDNA) as well as two nuclear genes TRMU and MTO1 encoding mitochondrial proteins.
Two Chinese families with aminoglycoside-induced and NSHL.
Clinical evaluations revealed incomplete penetrance (28.6% vs. 40.0%) and variable phenotype of hearing losses between two families. When the effect of aminoglycosides was excluded, the penetrances were both 0%. Sequence analysis of mitochondrial genomes showed a homoplasmic 1494C > T mutation in the12S rRNA gene (MT-RNR1) in all maternal relatives, as well as distinct sets of mtDNA polymorphism belonging to Eastern Asian haplogroups D4j and D5a2, respectively. However, none of these mtDNA variants was highly evolutionarily conserved and implicated to have functional significance. No mutations were identified in either TRMU or MTO1 gene.
Mitochondrial 1494C> T mutation is the molecular basis responsible for the NSHL of two families, and the use of aminoglycoside antibiotics can worsen the hearing of the mutation carriers. Our results indicate the importance of a systematic screening for the mitochondrial 1494C > T mutation in Chinese subjects in the prevention of aminoglycoside-induced and non-syndromic hearing loss.
We are happy to bring you news on a highly-anticipated book covering the scope of the auditory system coming this summer! It has become apparent that the function of the ear affects the function of the auditory nervous system and that pathologies of the peripheral parts of the auditory system can affect the function of the nervous system and vice versa. The classical separation of the auditory system in peripheral and central parts is therefore no longer valid. The third edition of Aage R. Møller's Hearing: Anatomy, Physiology, and Disorders of the Auditory System is dedicated to addressing this issue, as well as providing information on the auditory system, including its anatomy and disorders that affect specific areas like the middle ear and the cochlea. In addition, it introduces the role of neural plasticity in creating symptoms of diseases of hearing such as tinnitus, hypercusis, and phonophobia. Please read on for more.
Data from high-frequency hearing screening in adolescent students were analysed to investigate whether practices of listening to loud music are reflected in the hearing status of young people.
Students were screened for their hearing at frequencies 2, 4, and 6 kHz and at a level of 20 dB HL. Failure of the screening was defined by missing at least one frequency in one ear. In addition to hearing screening, the students filled out a questionnaire asking for practices related to exposure to loud music.
1296 adolescents aged 14 to 15 years.
The overall rate of failing the hearing screening was 14.9% (95% CI: 13.0%-16.8%). The rate was similar in adolescents with no, little, or moderate exposure to loud music (10% to 15%), but significantly increased (22% to 25%) in adolescents with high exposure.
The observed failing rate compares well to findings on the prevalence of hearing deficits in adolescents reported in other studies. In addition, our study suggests that the risk for hearing damage from loud music is not steadily increasing with increase of exposure, but exists only under conditions of extreme listening.
A cross-sectional epidemiological study on prevalence of hearing loss was carried out in an age- and Down's syndrome- stratified random sample of 1598 persons drawn from a base population of 9012 persons, representative of the Dutch adult population of intellectual disability (ID) service users. The re-weighted population prevalence is 30.3% (95% confidence interval [CI]: 27.7-33.0%). Subgroup prevalences range from 7.5% (95% confidence interval [CI]: 3.6-13.3) in the subgroup aged 18-30 years with ID by other causes than Down's syndrome, up to 100% (95% CI: 79.4-100%) in adults over 60 years of age with Down's syndrome. Down's syndrome (OR 5.18, 95% CI 3.80-7.07) and age were confirmed to be risk factors. Age-related increase in prevalence in persons with Down's syndrome appears to occur approximately three decades earlier, and in persons with ID by other causes approximately one decade earlier than in the general population.
The current study assessed the responses from a survey titled 'Life and Health - Young People 2005', completed by 2878 15-16-year-old adolescents in mainstream schools in the county of Orebro, Sweden. Thirty-nine percent of students with hearing loss (slight, mild, or moderate) and 6% of students with normal hearing reported tinnitus often or always during the past three months. Almost no gender difference was observed among students with normal-hearing reporting tinnitus (boys 6.3%, girls 5.6%); however, a gender difference was noticed among hard-of-hearing (HH) students (boys 50%, girls 28%). Adolescents with both hearing loss and tinnitus reported considerably higher scores for mental health symptoms, substance use, and school problems than other students. Anxiety in the past three months, male gender, and alcohol consumption in the past year were associated with tinnitus in HH students; irritation and anxiety in the past three months, disability, use of illicit drugs, and truancy predicted tinnitus in the normal-hearing group. Consequently, students with a hearing loss and tinnitus are at high risk and should be monitored for subsequent problems.
This paper investigated whether smoking and short stature in adulthood were independent risk factors for hearing loss. We reanalyzed data from the Danish Work Environment Cohort Study (an existing cohort study), on prevalence of self-reported hearing loss among 7,221 employees and on five-year incidence among 4,610 employees. We found that smoking predicted hearing loss incidence and prevalence. Smoking did not predict incidence at noise exposure during half or more of a worker's hours. Very short stature predicted prevalence in the total adult population only weakly, but strongly among employees born before 1951. These prospective findings indicate that smoking is an independent risk factor for incidence of hearing loss. Very short stature predicted prevalence of hearing loss only in a subpopulation.
A significant relationship between dietary nutrient intake and susceptibility to acquired hearing loss is emerging. Variability in the outcomes across studies is likely related to differences in the specific metrics used to quantify nutrient intake and hearing status. Most studies have used single nutrient analysis. Although this analysis is valuable, interactions between nutrients are increasingly recognized and could modify modeling of single nutrient effects. Therefore, we examined the potential relationship between diet and hearing using a metric of overall dietary quality.
This cross-sectional analysis was based on healthy eating index data and audiological thresholds.
Data for adults between the ages of 20 to 69 years of age were drawn from the National Health and Nutrition Examination Survey, 1999-2002.
Controlling for age, race/ethnicity, sex, education, diabetes, and noise exposure, we found a significant negative relationship (Wald F = 6.54, df = 4, 29; p ≤ 0.05) between dietary quality and thresholds at higher frequencies, where higher dietary quality was associated with lower hearing thresholds. There was no statistically significant relationship between dietary quality and threshold sensitivity at lower frequencies.
The current findings support an association between healthier eating and better high frequency thresholds in adults.
Interaural attenuation (IA) was evaluated for pure tones (frequency range 125 to 16000 Hz) using Sennheiser HDA 200 circumaural earphones and Telephonics TDH-39P earphones in nine unilaterally deaf subjects. Audiometry was conducted in 1-dB steps using the manual ascending technique in accordance with ISO 8253-1. For all subjects and for all tested frequencies, the lowest IA value for HDA 200 was 42 dB. The present IA values for TDH-39P earphones closely resemble previously reported data. The findings show that the HDA 200 earphones provide more IA than the TDH-39P, especially at lower frequencies (<or=500 Hz). It is concluded that contralateral masking should be applied during pure-tone audiometry with the HDA 200 earphones when the level at the test ear is more than 40 dB above the threshold of the non-test ear.
The Special Olympics Healthy Hearing Program provides a unique opportunity to determine the hearing service needs of individuals with mild intellectual disabilities participating in athletic endeavors in countries throughout the world. The Healthy Hearing Program screened 855 of 1800 athletes with intellectual disability over a period of a week at Nagano, Japan. Of 855 athletes screened, 58% passed the DPOAE screen and therefore required no further testing. Of the remaining 42%, 186 did not pass pure-tone screening. This number of athletes represents 21.8% of all athletes screened. Tympanometry outcomes for the 186 athletes failing pure-tone screening showed 56% (104) also failing this measure of middle-ear function. 65% of these 104 athletes' outer ear canals were blocked/partially-blocked with cerumen. This amount is in contrast to the 38% presence of cerumen for the 82 athletes failing pure-tone screening but passing tympanometry.
A data bank of prevalence of hearing impairment for monitoring and implementation of programmes at national or global level and for the estimate of the global burden has been established. A systematic search was conducted of random-sample population-based studies of bilateral hearing impairment with clearly defined hearing threshold levels. Fifty-three studies from 31 countries from all WHO regions were found to meet the selection criteria. The prevalence of mild and disabling hearing impairment and other details from the studies are reported by WHO region. Although a large number of studies were found, only a small number among them were suitable surveys of prevalence of bilateral hearing impairment in the general population. Hearing impairment is a major disability that should be monitored at all ages: more population-based surveys are needed in all regions of the world. Utilization of the WHO protocol is recommended for collection and analysis of data in standard ways; especially recommended is the use of WHO threshold levels and to report the prevalence of bilateral impairment, both of which required to calculate burden.
The time course of changes in perceived sound quality after hearing instrument fitting has not been studied systematically It is possible, for example, that patients may object to additional high frequency gain when fitted, but not after a period of auditory acclimatisation. The aim of this study was to utilise sound quality judgements to compare two frequency responses in new users at 4-week intervals over a 24-week post-fitting period. The null hypothesis was that there would be no change in sound quality judgements over time. A total of 16 elderly subjects were fitted monaurally with the same model of linear, programmable hearing instrument. This was set to a standard response that provided 26-29 dB of real-ear insertion gain at 2000 4000 Hz. This program was worn by the subjects for the duration of the study. All subjects reported greater than four hours of daily use. The alternative response which was used in a paired comparison paradigm, provided a mean gain reduction of 3, 8, 13, and 16 dB at 2000, 3000, 4000 and 6000 Hz, respectively. Subjects compared the standard and the alternative responses for sound quality along dimensions of comfort, clarity, and overall preference while listening to running speech presented in quiet, steady noise, and speech babble. At the time of fitting there was a small preference for the standard response when judging clarity, but the alternative response was preferred for comfort and preferred overall. Repeated-measures analysis of variance (ANOVA) for each quality dimension did not reveal any statistically significant change over time. It is concluded that this pattern of preference is unaffected by acclimatisation to amplification, at least over the initial 24 weeks of instrument use.
Evidence for the existence of auditory acclimatization is mixed, and the implications for clinical practice are unclear. The aim of this study was to seek evidence of perceived changes in performance over a 24-week post-fitting period. Thirty-two new, elderly subjects were recruited and fitted monaurally with the same model of linear, programmable hearing aid that provided in excess of 20-dB insertion gain at 2000-4000 Hz. The Glasgow Hearing Aid Benefit Profile (GHABP) was used to measure self-reported changes over time. The questions concerning benefit and satisfaction were modified to produce two versions: half of the subjects reported changes relative to the time of fitting, while the remainder reported changes relative to the previous occasion on which they completed the GHABP (3 weeks earlier). Subjects reported using hearing aids in excess of 90% of the time when in listening situations that cause difficulty. The median residual disability measure from the GHABP remained low (10-20%) over the duration of the study. The median scores for additional benefit and satisfaction showed a small but statistically significant improvement over the first 3 months of hearing aid use but only for the subjects who referenced this to their perceived performance 3 weeks earlier. The limited evidence for self-reported improvements in benefit and satisfaction over time reported to date must be tempered by the possibility of response bias arising from the method used to measure changes over time.
The objective of this study was to investigate electrode impedance in cochlear implant recipients in relation to electrically evoked stapedius reflex measurements during surgery, and to electrode design, stimulation mode, and T and C levels over a nine month period after surgery. Seventy-five implant recipients, implanted with a Nucleus straight electrode array or a Contour array, were included. The results show that: (1) during surgery electrode impedance decreases markedly after electrically evoked stapedius reflex measurements, (2) after surgery, during the period without stimulation until speech processor switch-on, impedance increases, (3) after processor switch-on impedance decreases. The lower impedance values after a period of stimulation are found at the higher T and C levels. Impedances of the straight array electrodes are lower than those of the Contour array. The difference corresponds mainly to their respective surface areas. In addition, the straight array shows a larger increase of impedance in the apical direction than the Contour array, probably because of the larger fluid environment around the basal electrodes of the straight array.
This review explores the association between GJB2 gene mutations, encoding connexin 26 (Cx26), and nonsyndromic hearing loss. Connexins are proteins that form intracellular membrane channels and regulate ion movement between contiguous fluid spaces. A family of autosomal gene mutations has been identified that lead to abnormal connexin expression within the inner ear that are associated with hearing loss. The exact mechanism by which this link is elicited remains unclear. We aim to highlight the clinically underestimated prevalence of GJB2 gene mutations, to explore the influential role of ethnic diversity in mutation frequency, and to provide a framework for hearing specialists in considering the differential diagnosis of nonsyndromic hearing loss. By linking an observed phenotype associated with abnormal Cx26 expression to the current understanding of the biological and genetic basis underlying it will allow a more accurate clinical description of associated hearing loss, and therefore enable more effective patient management and genetic counselling.
Investigate genetic causes of HI among the Inuit populations in the Arctic with a high prevalence of hearing impairment (HI).
A cross-sectional survey with population-based controls.
Forty-five patients, with sensorineural or mixed HI and an available blood sample for GJB2 sequencing from DNA, were selected from 166 east Greenlanders by specialist audiology examination, including pure-tone air and bone conduction audiometry from 125 Hz to 8000 Hz. Controls were 108 east- and 109 west-Greenlanders.
Forty-five patients with HI were included, 24 males and 21 females. Median age was 35 years (range: 5-76). The c.35delG allele frequency was 3.3%. One patient, homozygous for the c.35delG GJB2 mutation, had bilateral congenital profound HI. Another with mixed HI was heterozygous for the same mutation. Three were heterozygous for the p.V27I variant and one was heterozygous for the p.V153I variant. The frequency of the c.35delG mutation in the controls varied between 0.5% in west Greenland to 2.3% in east Greenland.
The c.35delG GJB2 mutation occurs in Greenland with low frequency. We conclude the main causes behind the prevalence of HI in this population are chronic otitis media, noise traumas, and/or unidentified genetic causes.
Serial audiograms were analysed for seven subjects, who were homozygous for the 35delG GJB2 mutation. The criterion for determining progression of hearing loss was at least a 1-dB loss in air conduction pure-tone average-3 (ACPTA-3) or ACPTA-4 per year for 2 to 10 years, with a minimum change of 10 dB ACPTA 3 or 4. Bilateral progression of hearing loss was found in 43% (3/7) of the subjects. A meta-analysis of seven studies with non-overlapping data sets and similar ascertainment criteria indicated that 19% of DFNB1 subjects with GJB2 mutations have progressive hearing loss. These data suggest that it may be incorrect to assume that congenital hearing loss due to this mutation is stable. We recommend rigorous audiologic surveillance for individuals with DFNB1.
The objective of this investigation was to determine the prevalence of Cx26 mutations in familial and sporadic cases of non-syndromic preverbal hearing impairment (HI). Molecular analysis of the Connexin 26 (Cx26/GJB2) gene was performed in 271 non-consanguineous individuals from the north of Italy, enrolled in the study because of the presence of non-syndromic preverbal sensorineural HI. One hundred and forty-six subjects (group 1) were referred from different ENT, paediatric and clinical genetic services, while 125 individuals (group 2) underwent Cx26 analysis based on precise anamnestic and clinical criteria for non-syndromic HI and low risk of acquired deficit. All of the cases were also classified as familial or sporadic due to the presence or absence of other documented childhood HI in the family. Of the total 271 individuals, 36.9% were positive for Cx26 mutations: 37 belonged to group 1 and 63 to group 2, which delineates a statistically significant difference between the two groups. The difference is mainly attributable to sporadically occurring cases. No significant differences between group 1 and group 2 were found regarding the prevalence of the common 35delG variant and the number of unidentified putative Cx26 alleles, although these latter were shown to be higher in sporadically occurring cases of the unselected group 1. The difference observed in Cx26 prevalence can be explained by the clinical selection of group 2, which ensures minimum risk of including cases of acquired HI. In particular, in cases of sporadically occurring HI, the use of a defined protocol increases the chances of a positive molecular result, improving genetic counselling and the possibility of establishing better genotype-phenotype correlation. Our data raise questions about the possible interpretation of Cx26 heterozygosity in a selected population of hearing-impaired individuals.
We studied the relationship between tinnitus pitch and the audiogram in 195 patients. Patients with tone-like tinnitus reported a higher pitch (mean = 5385 Hz) compared to those with a noise-like quality (mean = 3266 Hz). Those with a flat audiogram were more likely to report: a noise-like tinnitus, a unilateral tinnitus, and have a pitch < 2000 Hz. The average duration of bilateral tinnitus (12 years) was longer than that of unilateral tinnitus (5 years). Older subjects reported a less severe tinnitus handicap questionnaire score. Patients with a notched audiogram often reported a pitch <or=8000 Hz. Subjects with normal hearing up to 8000 Hz tended to have a pitch >or=8000 Hz. We failed to find a relationship between the pitch and the edge of a high frequency hearing loss. Some individuals did exhibit a pitch at the low frequency edge of a hearing loss, but we could find no similar characteristics among these subjects. It is possible that a relationship between pitch and audiogram is present only in certain subgroups.
The responses of several insert earphones in the Etymotic 3A series were measured with the occluded ear simulator (IEC 60711) and the 2cc coupler (IEC 60126). Acoustic clicks following a 100 us rectangular voltage pulse were compared. The peak-to-peak equivalent sound pressure levels in the ear simulator were found to be 9.2 dB greater than those in the 2cc coupler. The difference was independent of type of earphone among those tested. Similar comparisons were made for tone pips (brief tones or tone bursts) and continuous tones. For a given drive voltage, differences in earphone output were almost the same as the corresponding differences in published RETSPLs for the occluded ear simulator and 2cc coupler (ISO 389-2).
Input/output functions of the simultaneously recorded acoustic distortion product otoacoustic emissions (DPOAE) and neural frequency following-response distortion products (FFR-DP) at 2f1-f2 were evaluated to determine if these two representations of cochlear nonlinearity exhibit similar response behavior, which would suggest shared cochlear generators. Responses were recorded from normal-hearing adults for a tone burst stimulus pair (F1: 500 Hz; F2: 612 Hz) at 40-70 dB nHL. DPOAE responses were recorded from the ear canal, and FFR responses were recorded differentially from scalp electrodes, representing a vertical configuration. The input/output function for FFR-DP revealed a compressive saturating nonlinearity, whereas the DPOAE input/output function exhibited a linear growth at higher intensities following a compressive behavior at moderate levels. Results appear to suggest that cochlear generators may be contributing differentially to the acoustic and the neural distortion products. Also, FFR-DP responses appeared more identifiable and less variable, particularly at lower stimulus levels, than the corresponding DPOAE. These findings may point to a potential benefit of applying FFR testing to complement DPOAE in evaluating cochlear function at low frequencies.