Simultaneous miringoplasty and septoplasty, and the use of nasal septal perichondrium

Abstract To investigate the more ideal graft for optimal repair of tympanic membrane perforation, we examined the use of septal perichondrium in myringoplasty. Twenty-five patients with ages ranging between 18 and 54 were included in this study. All had a persistent, symptomatic tympanic membrane perforation, and nasal obstruction. All patients were scheduled for myringoplasty by a transmeatal approach in combination with septoplasty under general anaesthesia. Twenty-three patients had intact graft material and had more than 5 dB HL improvement in conductive hearing thresholds at least three frequencies in the follow up period. An overall success rate of 92 and 92% was recorded in terms of hearing improvement and perforation closure, respectively. Nasal septal perichondrium is easily accessible, cost-effective, time saving, sufficiently large, and patient friendly as a graft material in myringoplasty and has a good chance of postoperative survival.

from the European Archives of Oto-Rhino-Laryngology

Long, Loud iPod Use Can Cause Hearing Loss By Jodi Mailander Farrell

With the increasing popularity of MP3 players — and the loud, long listening habits of today’s youths — millions of children and teens are at a newfound risk of noise-induced hearing loss. Doctors around the country say they are seeing younger and younger patients with hearing-loss symptoms that typically don’t occur before middle age.

fromSci-Tech Today.com

Strides toward defining genetic signature of Alzheimer’s disease

Scientists have new information about the complex genetic signature associated with Alzheimer’s disease, the leading cause of cognitive decline and dementia in the elderly.

from Topix.net

Audiological Findings Among Workers from Brazilian Small-Scale Fisheries

Objective: The aim of this study was to examine the noise exposure and hearing of fishermen from small-scale fisheries from the state of Paraná in Brazil.

Design: Participants of this cross-sectional study included 141 male fishermen, ages ranging from 18 to 77 yr old and 136 controls matched by socioeconomic level, age, and gender. We conducted personal noise dosimetry and interviewed the fishermen regarding their hearing and their job. Audiological testing performed included pure-tone audiometry in the 0.5 to 8 kHz frequency range, extended high-frequency audiometry in the 9 to 16 kHz range, and transient and distortion-product otoacoustic emissions. Testing was preceded by a period of at least 14 hr without exposure to noise. Participants were subdivided in subgroups according to their noise exposure history.

Results: Sound level measurement results ranged from 38 to 58 Leq dB (A) in vessels without an engine and between 90 and 108 Leq dB (A) in vessels with an engine. Results from additional area sound level measurements conducted in five different seating locations in the 9HP engine boat ranged from 86 to 105 dB (A). Statistical analysis of the pure-tone audiometry results showed that fishermen with current or a history of occupational noise exposure had significantly poorer thresholds than controls or unexposed fishermen in several of the tested audiometric frequencies. Results of the otoacoustic emissions testing showed differences between exposed and unexposed groups regarding the presence of responses in bilateral amplitude and reproducibility at all frequency bands tested.

Conclusions: Because of the fishermen’s increased risk of hearing disorders, a variety of solutions are recommended, which include dissemination of information on control of noise emissions generated by the boat engines, audiological care, and hearing loss prevention services tailored to workers from small-scale fisheries.

from Ear and Hearing

Bone Conduction Auditory Steady State Response: Investigations into Reducing Artifact

Objectives: Auditory steady state responses (ASSRs) can be reliably recorded in sleeping neonates and can be used to estimate hearing thresholds in individuals with normal or impaired hearing. However, artifactual responses can contaminate recordings, particularly when recording bone conduction ASSRs. The aim of this investigation was to study the presence of electromagnetic artifact in bone conduction ASSRs and to investigate methods of reducing the amplitude of the artifact.

Design: Using a simulation of a patient, ASSR recordings were obtained to multiple frequency bone-conducted stimuli using the research MASTER system. ASSR stimuli were sinusoidal tones with the carrier frequencies 500, 1000, 2000, and 4000 Hz that were 100% amplitude modulated at 83, 87, 91, and 95 Hz, respectively. After the assessment of different equipment layouts, the effects of (1) altering the analog-to-digital conversion rates and (2) screening the transducer cable and B-71 transducer and connecting the screens to ground were investigated.

Results: For ASSR recordings, artifacts were observed at the modulation rates of the 1000-, 2000-, and 4000-Hz carrier frequencies. As expected, the artifact was proportional to stimulus intensity and was observed when using sampling rates of 1000 and 2000 Hz but not 1250 and 1600 Hz. Altering the electrode lead/transducer cable layout and orientation of the B-71 transducer significantly affected the amplitude of the artifact. Screening of the B-71 transducer and cable and connecting the screens to ground reduced the amplitude of the artifact to a level that was not significantly above background noise. A mu-metal screen had a significantly greater effect than aluminum or copper.

Conclusions: If stimulus artifact is present in the recorded EEG, for certain choices of carrier frequency and sampling rate it is possible to record artifactual signals at the same modulation rates as those used to elicit ASSRs. This is problematic as the artifact may then be misinterpreted as an ASSR response. The results from this study have demonstrated that careful attention to equipment layout, choice of sampling rate, using grounded screens to screen the B-71 transducer and transducer cable can all be effective in reducing the level of stimulus artifact.

from Ear and Hearing

Correlation between Audiovestibular Function Tests and Hearing Outcomes in Severe to Profound Sudden Sensorineural Hearing Loss

Objective: This study investigated whether audiovestibular function tests, namely auditory brain stem response (ABR) and vestibular-evoked myogenic potential (VEMP) tests were correlated to hearing outcomes after controlling the effects of other potential confounding factors in severe to profound sudden sensorineural hearing loss (SSHL).

Design: Eighty-eight patients with severe to profound SSHL were enrolled in this study. Pretreatment hearing levels, results of audiovestibular function tests, and final hearing outcomes were recorded from retrospective chart reviews. Other factors, including age, gender, delay of treatment, vertigo, diabetes mellitus, and hypertension, were collected as well. Comparative analysis between multiple variables and hearing outcomes was conducted using the cumulative logits model in overall subjects. Further, multivariate analysis of prognostic factors was conducted in the stratified groups of severe (70 dB HL 90 dB HL) SSHL.

Results: Multivariate analysis showed that pretreatment hearing levels, presence of vertigo, and results of ABR and VEMP testing were significant outcome predictors in the overall subjects. Stratification analysis demonstrated that both the presence of ABR and VEMP waveforms were significantly correlated with better hearing outcomes in the group of severe SSHL [ABR: adjusted odds ratio (aOR) = 14.7, 95% confidence interval (CI) = 1.78 to 122, p = 0.01; VEMP: aOR = 5.91, 95% CI = 1.18 to 29.5, p = 0.03], whereas the presence of vertigo was the only significant negative prognostic factor in the group of profound SSHL (aOR = 0.24, 95% CI = 0.06 to 0.95, p = 0.04). Other variables, including age, gender, diabetes mellitus, hypertension, and delay of treatment, were not significantly related to hearing outcomes in both groups (p > 0.05). A predictive hearing recovery table with the combined ABR and VEMP results was proposed for the group of severe SSHL.

Conclusions: ABR and VEMP tests should be included in the battery of neurootological examinations in patients with severe SSHL because the presence of both waveforms might indicate favorable hearing outcomes. The presence of vertigo might portend a worse prognosis in patients with profound SSHL. A presumed table in predicting hearing outcomes was suggested for patients with severe SSHL.

from Ear and Hearing

Development of a Mandarin Monosyllable Recognition Test

Objective: This study aimed to develop a set of 50- and 25-item word lists that exhibited familiarity, homogeneity, and phonemic balance for a Mandarin monosyllable recognition test (MMRT).

Design: To achieve the design goal of high subject familiarity with the test material, we selected the 700 most frequently occurring monosyllables to be the test material. The homogeneity of the test material was achieved by evaluating five psychometric characteristics of these 700 monosyllables to obtain 348 homogeneous monosyllables with similar psychometric functions for constructing the word lists. The phonemic balance of the 50-item word lists was achieved by deriving the desired numbers of initials, finals, and tones in these lists according to their occurrence frequencies in 4733 monosyllabic words. The phonemic balance of the 25-item word lists was achieved by equally dividing the desired numbers of initials, finals, and tones in the 50-item word lists into two groups, called half-A and half-B lists. Three half-A lists and three half-B lists were constructed from the 348 homogeneous monosyllables, and they could be paired to form nine 50-item word lists. Accordingly, all of the MMRT word lists are familiar, homogeneous, and phonemically balanced.

Results: The homogeneity of the MMRT word lists was examined by evaluating the interlist equivalence, interitem variability, and intersubject variability. A ?2 test was used to evaluate the interlist equivalence among the MMRT word lists; that is, to determine whether the values of percent correct recognition were distributed identically at 12 different presentation levels among the six 25-item word lists and nine 50-item word lists. No statistically significant differences were found among the word lists: ?2(55) = 12.004 and p = 1.000 for the six 25-item word lists, ?2(88) = 7.695 and p = 1.000 for the nine 50-item word lists, and ?2(154) = 19.699 and p = 1.000 for the six 25-item word lists plus nine 50-item word lists. The ?2 tests indicated that the six 25-item word lists and nine 50-item word lists exhibited interlist equivalence. The mean interitem variability (2.0 dB) and mean intersubject variability (2.3 dB) are lower for the MMRT word lists than for previously reported word recognition tests.

Conclusion: This study applied an innovative approach to design MMRT word lists from familiar and homogeneous monosyllables, in which the familiarity, homogeneity, and phonemic balance of the six 25-item and nine 50-item word lists were strictly controlled. These word lists exhibit interlist equivalence with respect to their psychometric functions and five psychometric characteristics; moreover, their interitem and intersubject variability are lower than those of previously reported lists. Future clinical experiments should examine whether such a design approach can improve the reliability and diagnostic sensitivity of word recognition tests for hearing-impaired listeners.

from Ear and Hearing

Effects of Hearing Loss and Spectral Shaping on Identification and Neural Response Patterns of Stop-Consonant Stimuli in Young Adults

Objectives: The primary purpose of this study was to more clearly define the effects of hearing loss, separate from age, on perception, and neural response patterns of dynamic spectral cues. To do this, the study was designed to determine whether (1) hearing loss affects the neural representation and/or categorical perception of stop-consonant stimuli among young adults and (2) spectrally shaped amplification aimed at increasing the audibility of the F2 formant transition cue reduces any effects of hearing loss. It was predicted that (1) young adults with hearing loss would differ from young adults with normal hearing in their behavioral and neural responses to stop-consonant stimuli and (2) enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus would not overcome the effects of hearing loss on behavioral performance or neural response patterns.

Design: Behavioral identification and neural response patterns of stop-consonant stimuli varying along the /b-d-g/ place-of-articulation continuum were measured from seven young adults with mild-to-moderate hearing impairment (mean age = 21.4 yr) and compared with responses from 11 young adults with normal hearing (mean age = 27 yr). Psychometric functions and N1-P2 cortical-evoked responses were evoked by consonant-vowel (CV) stimuli without (unshaped) and with (shaped) frequency-dependent amplification that enhanced F2 relative to the rest of the stimulus.

Results: Behavioral identification and neural response patterns of stop-consonant CVs differed between the two groups. Specifically, to the unshaped stimuli, listeners with hearing loss tended to make low-frequency judgments more often (more /b/, fewer /g/) than listeners with normal hearing when categorizing along the /b-d-g/ continuum. Additionally, N1 amplitudes were larger and P2 latencies were longer to all phonemes in young adults with hearing impairment versus normal hearing. Enhancing the audibility of the F2 transition cue with spectrally shaped amplification did not alter the neural representation of the stop-consonant CVs in the young listeners with hearing loss. It did modify categorical perception such that listeners with hearing loss tended to make high-frequency judgments more often (more /g/, fewer /b/). However, shaping the stimuli did not make their psychometric functions more like those of the normal controls. Instead, young adults with hearing loss went from one extreme (low-frequency judgments with unshaped stimuli) to the other (high-frequency judgments with shaped stimuli), whereas judgments from the normal controls were more balanced.

Conclusions: Hearing loss, separate from aging, seems to negatively impact identification and neural representation of time-varying spectral cues like the F2 formant transition. Enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus does not overcome the effects of hearing loss on behavioral performance or neural response patterns in young adults. Thus, the deleterious effects of hearing loss on stop-consonant perception along the place-of-articulation continuum may not only be due solely to decreased audibility but also due to improper coding by residual neurons, resulting in distortion of the time-varying spectral cue. This may explain, in part, why amplification cannot completely compensate for the effects of sensorineural hearing loss.

from Ear and Hearing

Frequency Tuning Curves Derived from Auditory Steady State Evoked Potentials: A Proof-of-Concept Study

Objectives: Assess the feasibility of drawing tuning curves from the masking function of steady state potentials. Develop a noninvasive tool for research applications on cochlear frequency selectivity in sedated animals. Obtain pilot human data validating auditory steady state evoked potential-derived (ASSEP) tuning curves against psychophysical data.

Design: ASSEP tuning curves were drawn in 10 Beagle puppies and six human adults using amplitude-modulated probes. Two probe frequencies (1 and 2 kHz) were used in dogs and only one (2 kHz) in humans. The modulation rates of the two probes were set to 81 and 88 Hz, respectively. Psychophysical tuning curves were obtained in 12 normal human subjects using the same maskers and either a pure-tone or an amplitude-modulated probe to verify if the latter had a specific effect on tuning curve parameters. Six of these 12 subjects participated in the electrophysiologic measurements. For each tuning curve, the intensity of the narrowband masker required just to mask the fixed probe was plotted for different masker center frequencies. Masker center frequencies extended to about half an octave above and an octave below the probe frequencies in 100-Hz steps. Tuning curve width (Q10 dB values), high- and low-frequency slopes (in dB/octave) and the masker frequency yielding the lowest masking threshold (maximal masker frequency) were computed. Canine Q10 dB values obtained were compared with those published for several species with other techniques. For humans, ASSEP and psychophysical tuning curves were directly compared in the same subjects and with published data.

Results: In dogs, the ASSEP method yielded reproducible tuning curves with qualitative and quantitative parameters similar to other physiologic measures of tuning obtained in various animals. Q10 dB values were greater at 2 than at 1 kHz, reflecting the well-known correlation between sharpness of tuning and central frequency. In humans, ASSEP Q10 dB values were slightly smaller than the psychophysical ones, but were greater by a factor of 2 than those obtained with previously published electrophysiologic procedures. In both species, detuning-a shift of the tip of the curve away from the probe frequency-was frequently observed as upward shifts with a maximal value of 200 Hz. Human psychophysical tuning curves also showed a certain amount of upward detuning. The intraindividual comparison of the two types of probes performed on human subjects with the psychophysical method did not indicate a specific effect of the amplitude-modulated probe on the curve parameters. Neither did the intraindividual comparisons indicate that an amplitude-modulated probe per se promoted detuning. Detuning has been observed with several other techniques and is usually attributed to nonlinear interactions between masker and probe in simultaneous masking.

Conclusions: The results demonstrate the feasibility of measuring realistic ASSEP tuning curves in sedated dogs and in sleeping human adults. The ASSEP tuning curves exhibit a series of classical features similar to those obtained with time-honored methods. These results pave the way for the development of a noninvasive electrophysiologic method for tuning curve recording and its applications in noncooperative experimental animals or clinical subjects.

from Ear and Hearing

Morphology Studies of the Human Fetal Cochlea in Turner Syndrome

Objectives: Turner syndrome (TS) is the most frequent sex chromosome abnormality, and sensorineural hearing loss is common. We aimed to determine whether there are consistent morphologic cochlear abnormalities during gestational development that could be associated with TS.

Design: The histology of nine fetal temporal bones of TS autopsied after spontaneous abortion was studied.

Results: Gross morphologic examination of the TS cochleae failed to reveal a pattern of structural abnormalities that would explain the development of sensorineural hearing loss. Mondini-like cochlear dysplasia was observed in one 13-wk-old TS fetus.

Conclusion:

We could not demonstrate a consistent pattern of cochlear malformations.

from Ear and Hearing

Multiple Auditory Steady State Responses (80-101 Hz): Effects of Ear, Gender, Handedness, Intensity and Modulation Rate

Objective: To evaluate how the amplitudes and latencies of auditory steady state responses (ASSRs) to multiple stimuli presented at rates between 80 and 101 Hz vary with the ear of stimulation, the handedness or gender of a subject, and the rate and intensity of the stimuli.

Design: ASSRs were recorded in a group of 56 young adults (27 females, 13 left handed) using several stimulus conditions. In the two main conditions, four sinusoidally amplitude-modulated tones (each uniquely modulated using rates between 80 and 105 Hz) with carrier frequencies of 500, 1000, 2000, and 4000 Hz, were presented concurrently to each ear (eight total). In the first condition the modulation rates for the left ear were slower than those for the right and in the second condition this relationship was reversed. Other conditions evaluated the responses to single stimuli, to multiple stimuli presented in one ear only and to multiple stimuli presented dichotically (four in each ear) with rates that decreased rather than increased with increasing carrier frequency. Stimuli were presented at an intensity of 73 dB SPL except in two conditions wherein the intensity was 53 dB SPL.

Results: At 73 dB SPL, multiple-stimulus ASSRs were significantly reduced (monotic or dichotic) compared with single-stimulus ASSRs, especially at 1000 and 2000 Hz. There were significant differences between monotic and dichotic stimulation. When the stimuli were presented dichotically, the amplitude of the response varied with the relative rates of modulation for the stimuli presented in each ear. ASSRs were larger in the ear with the higher rate when the carrier frequencies were 500 and 1000 Hz and when the modulation rates were <90 Hz. There were no consistent effects of gender or ear of stimulation. There were also no significant effects of handedness.

Conclusions: Presenting multiple stimuli at 73 dB SPL in the same ear decreases the amplitude of the ASSR compared with when the stimuli are presented singly. This is caused by the masking effect of low on higher carrier frequencies and some other inhibitory effect of high on lower frequencies. Dichotic stimulation can increase the amplitude of the response to stimuli modulated more rapidly (and concomitantly decrease the responses to the stimuli modulated more slowly). This effect occurs only for carrier frequencies <2000 Hz and for modulation frequencies <90 Hz. Dichotic stimulation also causes a small but highly significant decrease in the latency of the response compared with monotic stimulation.

from Ear and Hearing

Perception of Envelope-Enhanced Speech in the Presence of Noise by Individuals with Auditory Neuropathy

Objective: To investigate the effect of background noise on perception of unprocessed and envelope-enhanced speech in individuals with auditory neuropathy (AN).

Design: Open-set speech identification abilities were assessed for unprocessed and envelope-enhanced speech in quiet and at three signal to noise ratios (10, 5, and 0 dB signal to noise ratio) in 15 individuals with AN.

Results: Results revealed that speech identification ability was affected more in the presence of noise than in quiet. The participants were classified into two groups, Good Performers and Poor Performers, based on their speech identification scores in quiet. It was observed that the reduction in mean speech identification scores in noise was less for Good Performers when compared with that of Poor Performers. Envelope enhancement of the signal improved speech identification scores in both the groups. The analysis of results also showed that Good Performers showed a significant improvement in all the conditions, whereas Poor Performers showed improvement only in quiet and +10 dB signal to noise ratio.

Conclusions: For individuals with AN, listening in background noise is more difficult than in quiet condition. Envelope enhancement of speech signal improves speech identification scores in quiet and in background noise for individuals with AN. However, the benefit obtained varies depending on the speech identification ability in quiet.

from Ear and Hearing

Prevalence of GJB2 (Connexin-26) and GJB6 (Connexin-30) Mutations in a Cohort of 300 Brazilian Hearing-Impaired Individuals: Implications for Diagnosis and Genetic Counseling

Objective: Hereditary nonsyndromic deafness is an autosomal recessive condition in about 80% of cases, and point mutations in the GJB2 gene (connexin 26) and two deletions in the GJB6 gene (connexin 30), del(GJB6-D13S1830) and del(GJB6-D13S1854), are reported to account for 50% of recessive deafness. Aiming at establishing the frequencies of GJB2 mutations and GJB6 deletions in the Brazilian population, we screened 300 unrelated individuals with hearing impairment, who were not affected by known deafness related syndromes.

Methods: We firstly screened the most frequently reported mutations, c.35delG and c.167delT in the GJB2 gene, and del(GJB6-D13S1830) and del(GJB6-D13S1854) in the GJB6 gene, through specific techniques. The detected c.35delG and c.167delT mutations were validated by sequencing. Other mutations in the GJB2 gene were screened by single-strand conformation polymorphism and the coding region was sequenced when abnormal patterns were found.

Results: Pathogenic mutations in GJB2 and GJB6 genes were detected in 41 individuals (13.7%), and 80.5% (33/41) presented these mutations in homozygosis or compound heterozygosis, thus explaining their hearing defect. The c.35delG in the GJB2 gene was the most frequent mutation (37/300; 12.4%), detected in 23% familial and 6.2% the sporadic cases. The second most frequent mutation (1%; 3/300) was the del(GJB6-D13S1830), always found associated with the c.35delG mutation. Nineteen different sequence variations were found in the GJB2 gene. In addition to the c.35delG mutation, nine known pathogenic alterations were detected c.167delT, p.Trp24X, p.Val37Ile, c.176_191del16, c.235delC, p.Leu90Pro, p.Arg127His, c.509insA, and p.Arg184Pro. Five substitutions had been previously considered benign polymorphisms: c.-15C>T, p.Val27Ile, p.Met34Thr, p.Ala40Ala, and p.Gly160Ser. Two previously reported mutations of unknown pathogenicity were found (p.Lys168Arg, and c.684C>A), and two novel substitutions, p.Leu81Val (c.G241C) and p.Met195Val (c.A583G), both in heterozygosis without an accompanying mutation in the other allele. None of these latter four variants of undefined status was present in a sample of 100 hearing controls.

Conclusions: The present study demonstrates that mutations in the GJB2 gene and del(GJB6 D13S1830) are important causes of hearing impairment in Brazil, thus justifying their screening in a routine basis. The diversity of variants in our sample reflects the ethnic heterogeneity of the Brazilian population.

from Ear and Hearing

Receptive Vocabulary Development in Deaf Children with Cochlear Implants: Achievement in an Intensive Auditory-Oral Educational Setting

Objectives: Deaf children with cochlear implants are at a disadvantage in learning vocabulary when compared with hearing peers. Past research has reported that children with implants have lower receptive vocabulary scores and less growth over time than hearing children. Research findings are mixed as to the effects of age at implantation on vocabulary skills and development. One goal of the current study is to determine how children with cochlear implants educated in an auditory-oral environment compared with their hearing peers on a receptive vocabulary measure in overall achievement and growth rates. This study will also investigate the effects of age at implant on vocabulary abilities and growth rates. We expect that the children with implants will have smaller vocabularies than their hearing peers but will achieve similar rates of growth as their implant experience increases. We also expect that children who receive their implants at young ages will have better overall vocabulary and higher growth rates than older-at-implant children.

Design: Repeated assessments using the Peabody Picture Vocabulary Test were given to 65 deaf children with cochlear implants who used oral communication, who were implanted under the age of 5 yr, and who attended an intensive auditory-oral education program. Multilevel modeling was used to describe overall abilities and rates of receptive vocabulary growth over time.

Results: On average, the deaf children with cochlear implants had lower vocabulary scores than their hearing peers. However, the deaf children demonstrated substantial vocabulary growth, making more than 1 yr’s worth of progress in a year. This finding contrasts with those of previous studies of children with implants, which found lower growth rates. A negative quadratic trend indicated that growth decelerated with time. Age at implantation significantly affected linear and quadratic growth. Younger-at-implant children had steeper growth rates but more tapering off with time than children implanted later in life.

Conclusions: Growth curves indicate that children who are implanted by the age of 2 yr can achieve receptive vocabulary skills within the average range for hearing children.

from Ear and Hearing

Relation of Electrically Evoked Compound Action Potential Thresholds to Behavioral T- and C-Levels in Children with Cochlear Implants

Objective: This study examined the relation of electrically evoked compound action potential thresholds obtained using neural response telemetry (NRT) to T- and C-levels in children’s speech processor programs optimized for recognition of very soft to loud sounds while ensuring tolerance of very loud sounds.

Design: Forty-one children (age 2 to 14 yr) with stable electrical hearing participated. All children were Nucleus 24 System recipients and attended one of three auditory-oral schools that have on-site pediatric audiologists experienced at cochlear implant programming. Speech processor MAPs were created and adjusted over a period of months until aided warble-tone thresholds were between 10 and 30 dB HL at octave frequencies between 250 and 4000 Hz, and understanding of speech was maximized for many listening situations. At least 1 yr postactivation, visual (vNRT) and predicted (tNRT) thresholds were obtained on 9 to 11 electrodes and compared to each child’s T- and C-level values on these electrodes in their MAPs. Test-retest stability of NRT thresholds was compared for two test sessions 1 mo apart.

Results: NRT-based evoked compound action potential thresholds could be obtained from 36 of the 41 children. vNRT and tNRT test-retest reliability was high; average correlation coefficients (r) across subjects were 0.90 (range: 0.64 to 0.99) and 0.88 (range: 0.31 to 1.00), respectively. Group average correlation coefficients between vNRT and T-level, vNRT and C-level, tNRT and T-level, and tNRT and C-level were low (0.18, 0.21, 0.24, and 0.26, respectively). Group mean tNRT thresholds were four current levels lower than the group mean vNRT thresholds. Subsequent analysis was performed with the vNRT thresholds because the range of test-retest correlation coefficients for individual subjects was narrower than with tNRT. Hierarchical linear modeling was used to determine if vNRT could be used to predict T- and C-levels. This analysis indicated a significant average relation between vNRT and T-levels and between vNRT and C-levels, but significant heterogeneity in the individual-level estimates of those relations. In other words, subjects varied significantly in the size of the relation between their individual vNRT values and both T- and C-levels. Attempts to account for that heterogeneity did not identify any subject characteristics that were significantly related to the individual-level parameters.

Conclusions: The position of the group average vNRT and tNRT thresholds in the upper half of the dynamic range between Ts and Cs agrees with previous studies. The fact that the profile of vNRT thresholds did not parallel the profiles of Ts and Cs across electrodes for most children suggests that simply shifting the NRT profile to select T- and C-levels in initial MAPs is likely to result in a loudness imbalance for certain speech frequencies and/or tolerance issues for many children. This was verified by the hierarchical linear modeling analysis, which showed substantial and significant heterogeneity in the relations between vNRT and T-levels and between vNRT and C-levels. In summary, vNRT is not related to T- or C-levels in a simple and uniform way that would allow it to guide MAP fine tuning with any precision. Consequently, it is recommended that MAP fine tuning be based on the child’s behavioral responses on individual electrodes.

from Ear and Hearing