Sound-direction identification, interaural time delay discrimination, and speech intelligibility advantages in noise for a bilateral cochlear implant user

OBJECTIVES

To characterize some of the benefits available from using two cochlear implants compared with just one, sound-direction identification (ID) abilities, sensitivity to interaural time delays (ITDs) and speech intelligibility in noise were measured for a bilateral multi-channel cochlear implant user.

METHODS

Sound-direction ID in the horizontal plane was tested with a bilateral cochlear implant user. The subject was tested both unilaterally and bilaterally using two independent behind-the-ear ESPRIT (Cochlear Ltd.) processors, as well as bilaterally using custom research processors. Pink noise bursts were presented using an 11-loudspeaker array spanning the subject's frontal 180 degrees arc in an anechoic room. After each burst, the subject was asked to identify which loudspeaker had produced the sound. No explicit training, and no feedback were given. Presentation levels were nominally at 70 dB SPL, except for a repeat experiment using the clinical devices where the presentation levels were reduced to 60 dB SPL to avoid activation of the devices' automatic gain control (AGC) circuits. Overall presentation levels were randomly varied by +/- 3 dB. For the research processor, a "low-update-rate" and a "high-update-rate" strategy were tested. Direct measurements of ITD just noticeable differences (JNDs) were made using a 3 AFC paradigm targeting 70% correct performance on the psychometric function. Stimuli included simple, low-rate electrical pulse trains as well as high-rate pulse trains modulated at 100 Hz. Speech data comparing monaural and binaural performance in noise were also collected with both low, and high update-rate strategies on the research processors. Open-set sentences were presented from directly in front of the subject and competing multi-talker babble noise was presented from the same loudspeaker, or from a loudspeaker placed 90 degrees to the left or right of the subject.

RESULTS

For the sound-direction ID task, monaural performance using the clinical devices showed large mean absolute errors of 81 degrees and 73 degrees, with standard deviations (averaged across all 11 loud-speakers) of 10 degrees and 17 degrees, for left and right ears, respectively. Fore bilateral device use at a presentation level of 70 dB SPL, the mean error improved to about 16 degrees with an average standard deviation of 18 degrees. When the presentation level was decreased to 60 dB SPL to avoid activation of the automatic gain control (AGC) circuits in the clinical processors, the mean response error improved further to 8 degrees with a standard deviation of 13 degrees. Further tests with the custom research processors, which had a higher stimulation rate and did not include AGCs, showed comparable response errors: around 8 or 9 degrees and a standard deviation of about 11 degrees for both update rates. The best ITD JNDs measured for this subject were between 350 to 400 microsec for simple low-rate pulse trains. Speech results showed a substantial headshadow advantage for bilateral device use when speech and noise were spatially separated, but little evidence of binaural unmasking. For spatially coincident speech and noise, listening with both ears showed similar results to listening with either side alone when loudness summation was compensated for. No significant differences were observed between binaural results for high and low update-rates in any test configuration. Only for monaural listening in one test configuration did the high rate show a small significant improvement over the low rate.

CONCLUSION

Results show that even if interaural time delay cues are not well coded or perceived, bilateral implants can offer important advantages, both for speech in noise as well as for sound-direction identification.

Does cochlear reimplantation affect speech recognition?

Although cochlear implantation has been proven to be a very effective method of rehabilitation for post-lingually deaf adults and pre-lingually deaf children, as electronic devices, cochlear implants are occasionally subject to damage or breakdowns. In these cases, reimplantation would be necessary. The aim of this study was to find out whether or not there are any negative effects on speech abilities after reimplantation with the same type of multichannel digital implant in the same ear. Seven patients were provided with a digital multi-channel cochlear implant. One subject suffered manipulative damage to the implant, and in six subjects an implant failure was observed. All reimplantations were performed on the same ear as the initial implantation. with the same implant type. Parameters such as insertion depth and number of active channels were the same in all subjects before and after reimplantation. Immediately following the revision surgery, three patients attained the same level of hearing that they had with their original implants. Three months following reimplantation, five subjects achieved almost the same scores that they had before reimplantation. The results showed that cochlear implant patients undergoing re-implantation can anticipate achieving nearly the same level of speech recognition as they had with their original implant. Nevertheless, patients need to be aware of potential problems before undergoing reimplantation so that expectations are not too high.

The educational settings of profoundly deaf children with cochlear implants compared with age-matched peers with hearing aids: implications for management

The educational settings of 42 implanted profoundly deaf children 3 years after implantation were compared with the respective settings of 635 age-matched severely deaf and 511 profoundly deaf children with hearing aids. All implanted children received their implants before beginning school. The results revealed that 3 years after implantation. 38% (16 children) of the implanted profoundly deaf children attended mainstream schools, whereas 57% (24 children) were in a unit, or special class, in a mainstream school, and 5% (two children) were in schools for the deaf. With regard to the age-matched profoundly deaf children with hearing aids, 12% (63 children) attended mainstream schools, whereas 55% (281 children) were in a unit of a mainstream school, and 33% (167 children) were in schools for the deaf. In the group of age-matched severely deaf children, 38% (239 children) attended mainstream schools, whereas 51% (326 children) were in a unit of a mainstream school, and 11% (70 children) were in schools for the deaf. Statistical analysis revealed a highly significant difference between the educational placement of implanted children and hearing-aided profoundly deaf children (p<0.00001), whereas there was no statistically significant difference between implanted children and hearing-aided severely deaf children. In conclusion, implanted profoundly deaf children who have received their implants before beginning school have the same profile of educational placement as aided severely deaf children rather than aided profoundly deaf children of the same age in the UK. This is likely to have significant implications for the future management of profoundly deaf children and to influence future planning of educational support services.

[Cochleography and cochlear view as the way of assessment of successful surgical inner ear implantation]

115 cochlear implantation were performed in ENT Department Karol Marcinkowski University of Medical Sciences in Poznań in 1994-2001. Nucleus Mini System 22 and Nucleus 24 of Cochlear Ltd were used in these operations. Two approaches were performed: middle fossa approach in one case and traditional one. The aim of this study was evaluation of cochleogram and cochlear view as the ways of assessment of successful inner ear implantation. One of X-ray projection were performed in implanted patients 24 hours after implantation. In cochleograms the degree of electrodes rotation in cochlea was calculated. The number of inserted electrodes in cochlea was calculated in cochler view projection. Described X-ray projection were performed in 70 patients. On X-ray projection (cochleograms) rotation degree of electrodes in majority were equal or higher than 250 grades (according to literature it is sufficient for successful speech rehabilitation). X-ray projection--cochlear view confirmed full insertion of electrode.

Speech recognition in background noise of cochlear implant patients

OBJECTIVES

The performances of adult patients using Spectral peak (Nucleus 22 or Nucleus 24 patients) or Continuous Interleaved Sampling or Advanced Combination Encoder (Clarion patients) were evaluated in their ability to perform in quiet and in 2 levels of background noise.

PATIENTS AND METHODS

Ninety-six patients were tested with the City University of New York Sentences presented at 70 dB in quiet and at signal-to-noise ratios (SNR) of +10 and +5 dB. Patients were scored on the number of words perceived correctly.

RESULTS

Scores were different at each condition (P < 0.05): 88% words correct in quiet, 73% correct at an SNR of +10 dB, and 47% correct at an SNR of +5 dB. Linear regression analysis found no significant correlation between test score and age at implantation or time using the implant. A weak negative correlation was found between years of hearing loss and score.

CONCLUSION

Competing noise interferes with comprehension of connected speech for most cochlear implant patients.

Comparison of methods in speech acquisition research

The paper examines the effect of choices involved in speech acquisition research among children with impaired hearing. Choices involving transcription method, sampling procedures, subject selection and statistical approaches affect the outcome of any research. Two recent papers used different methodological approaches to examine the conversational speech samples of children with impaired hearing and arrived at differing conclusions about their rates of improvement. To compare these results, a further data set was examined using both methodologies. The analyses indicated a closer alignment of results than was immediately obvious from the two previous studies, suggesting that the different results were primarily due to differences in methodology.

Binaural cochlear implants placed during the same operation

OBJECTIVE

To evaluate the binaural listening advantages for speech in quiet and in noise and to localize sound when independently programmed binaural cochlear implants are used, and to determine whether ears with different hearing ability and duration of profound deafness perform differently with cochlear implants as well as to what extent preimplant psychophysical and physiologic assessment could be predictive of performance.

STUDY DESIGN

Prospective study in which patients were prospectively selected to undergo bilateral implantation during a single surgical procedure at a tertiary referral center. All testing was performed with patients using their right, left, or both cochlear implants. Preimplant and intraoperative measures used electrical stimulation at the round window and stimulation through the cochlear implant.

RESULTS

Bilateral implantation during the same operation did not cause any postoperative problems such as severe vertigo or ataxia. At 1 year, results of speech testing in quiet demonstrated a binaural advantage for 2 of 10 subjects. Speech-in-noise testing demonstrated that two implants were beneficial for two individuals. All subjects benefited from a head shadow effect when an ear with a better signal-to-noise ratio was available. The ability to localize sound was improved with binaural implants in all subjects. Preimplant psychophysical or physiologic measures were not predictive of eventual speech perception performance.

CONCLUSION

Binaural cochlear implants can assist in the localization of sounds and have the potential in some individuals to improve speech understanding in quiet and in noise.

Speech perception and language criteria for paediatric cochlear implant candidature

Existing criteria for cochlear implantation of children with impaired hearing aim to select children who will eventually achieve better speech perception scores with an implant than with a hearing aid. It is difficult to predict the eventual outcomes with hearing aid and implant because speech perception scores typically increase with age, and because the distribution of scores for implant and hearing aid users overlap considerably at all ages. This paper shows how speech perception scores can be combined with spoken language measures to arrive at an objective criterion for implant selection. The method also allows estimation of the likely increase in speech perception score within a few months of implantation and estimation of the probability that the child will perform better with the implant than the hearing aid. The criteria were based on data from 135 evaluations of 50 children using cochlear implants with monosyllabic words, open-set sentences, the Clinical Evaluation of Language Fundamentals, and the Peabody Picture Vocabulary Test. Data from 114 evaluations of 43 children using hearing aids were used to illustrate the sensitivity of the criteria.

A multidimensional scaling analysis of tone discrimination ability in Cantonese-speaking children using a cochlear implant

Tone discrimination testing with two groups of profoundly hearing-impaired children using a cochlear implant and one group of normally hearing children suggests that pitch level is perceptually more salient than pitch contour. In this paper, the discrimination results from these children are submitted to a multidimensional scaling analysis to determine what differences if any exist between the children in the information they use to discriminate between tone types. Through the multidimensional scaling analysis it is shown that, 'average pitch height' and 'pitch direction' are the most salient acoustic features in tone with pitch height being perceptually more important than pitch level. Furthermore, these acoustic features are similarly salient for all three groups of children despite differences in the source of auditory information and linguistic experience. Finally, the two groups of cochlear implant users who employ different speech processing strategies with their implant are shown to be distinguishable by differences in the relative salience of pitch direction.

Tone discrimination in Cantonese-speaking children using a cochlear implant

Most tone perception tests for Cantonese-speaking cochlear implant users have been based on tone identification tasks which require significant cognitive development to be successfully completed. Results from such tests suggest that cochlear implant child users are performing at about chance level and may not be receiving much information about pitch using the implant. This paper reports on the ability of cochlear implant child users to discriminate pitch variations in Cantonese by using an experimental procedure based on play audiometry. As part of the study, the usefulness of higher rates of electrode stimulation for aiding tone discrimination is also examined. Cochlear implant users are shown to derive sufficient information about pitch to discriminate most tone contrasts relatively successfully, with performance being most variable for contrasts involving tones clustered in the lower register of the speaker's fundamental frequency range. Contrary to hypothesis, higher electrode stimulation rates are not found to offer significant benefits for aiding pitch discrimination.

Relationship of intraoperative electrically evoked stapedius reflex thresholds to maximum comfortable loudness levels of children with cochlear implants

Previous studies of the relationship between the intraoperatively obtained electrically evoked stapedius reflex threshold (ESRT) and the maximum comfortable loudness (MCL) values used to program the speech processor of cochlear implant (CI) patients have indicated that ESRTs provide an inexact estimate of MCL. In order to determine whether this estimate might be more exact for electrodes in different parts of the electrode array, we studied the electrode-specific relationships between ESRT and MCL in 29 Med-E1 Combi 40+ and 25 Nucleus CI 24 M patients after first fitting of the speech processor and 2 and 6 months later. The MCL values were mostly less than the ESRT values, but increased progressively over the first 6 months, reaching 83% and 72% of the ESRT values, on average, across all electrodes for the Med-E1 and Nucleus systems respectively. The population variation across electrodes decreased over the 6-month observation period and was least for the apical half of the array, for which the correlation coefficients of regressions between ESRT and MCL were around 0.65 for both systems. These results indicate that estimates of MCL values from the ERST are more accurate for the apical half of the intra-cochlear array and could then be described by an offset value plus an increase of MCL by 0.62 and 0.53 of ESRT for the Med-E1 and Nucleus systems, respectively.

Effects of training on timbre recognition and appraisal by postlingually deafened cochlear implant recipients

The purpose of this study was to compare the effect of structured training on recognition and appraisal of the timbre (tone quality) of musical instruments by postlingually deafened cochlear implant recipients. Twenty-four implant users (Nucleus CI24M) were randomly assigned to a control or a training group. The control group experienced only incidental exposure to music in their usual daily routine. The training group participated in 12 weeks of training delivered via a laptop computer in which they were introduced to excerpts of musical instruments representing three frequency ranges and four instrumental families. Those implant recipients assigned to the training group showed significant improvement in timbre recognition (p < .0001) and timbre appraisal (p < .02) compared to the control group. Correlations between timbre measures and speech perception measures are discussed.

Postlingual collapse of language and its recovery after cochlear implantation

A 6-year-old boy lost his normally-developed language ability within 2 months after bilateral sudden peripheral deafness. The boy became non-communicative with others, restless with frequent meaningless bursts of shouts (communication skills equivalent to 9-11 months of language development: a rapid breakdown of language). Since conservative methods were ineffective, cochlear implantation was performed. A surprising success was observed: he regained the language retracing the normal developmental stages and caught up with his contemporaries in 2 years. Behavioral improvement paralleled his language development. This case (1) provides insights into the brain function with respect to language acquisition, in relation to the plasticity during the 'critical period' of language learning, (2) reveals the close relationship between language development and behavior, and (3) suggests the predominance of auditory stimulation in learning language.

The role of age in pediatric cochlear implantation

OBJECTIVE

To document progress, benefit and importance of age in paediatric cochlear implantation.

DESIGN

The EARS (Evaluation of Auditory Responses to Speech) test battery was performed on 33 prelingually deaf children at regular intervals up to 36 months following implantation. All children participated in individually tailored intensive audiological rehabilitation programs after receiving their implants. In this respect, it was attempted to evaluate speech perception scores in children implanted before and after the age of 3 in a homogenous group.

RESULTS

All children demonstrated encouraging improvements over time in their speech recognition abilities. Furthermore, it was observed that the children who were implanted under the age of 3 achieved higher levels of speech perception performance.

CONCLUSION

In order to shorten the process of central maturation of the auditory system, it is desirable to implant the children as young as possible. Early intervention seems to be the ideal strategy in enabling prelingually deaf children to derive maximum benefit from cochlear implantation.

Sending sound to the brain

The cochlear implant, a microelectrode array that directly stimulates the auditory nerve, has greatly benefited many individuals with profound deafness. Deaf patients without an intact auditory nerve may be helped by the next generation of auditory prostheses: surface or penetrating auditory brainstem implants that bypass the auditory nerve and directly stimulate auditory processing centers in the brainstem.

Three-month results with bilateral cochlear implants

OBJECTIVES

To evaluate possible binaural listening advantages for speech in quiet, speech in noise, and for localization in a group of postlingually deafened adults with two cochlear implants functioning independently after 3 mo experience.

DESIGN

Nine postlingually deafened subjects who had received a Cochlear Corporation CI24M implant in each ear were evaluated on a number of tasks. The subjects all had audiometric or biographical (e.g., duration of deafness) differences between the ears. Word and sentence materials were presented to the subjects in quiet and in noise with the signal always in the front and the noise from the front or either side. Results are reported for each ear and for both ears with the noise on either side. This allowed evaluation of head shadow and squelch effects. Additionally, localization ability was assessed for broadband noise presented either to the right or left of center at 45 degrees azimuth. Localization was assessed for each ear and for both ears.

RESULTS

Results of speech testing in quiet showed a significant advantage for the binaural condition over the better ear in four subjects. In noise, with both signal and noise in front of the subject, a significant advantage of two ears over the better ear was found for four subjects. For noise to one side of the head, when the ear opposite the noise source was added to the ear ipsilateral to the noise, a significant advantage was demonstrated for seven of seven tested subjects. When the ear ipsilateral to the noise was added to the ear contralateral to the noise, a significant advantage was shown for only one of seven (noise on right) and three of seven (noise on left) tested subjects. The localization task showed that all seven tested subjects could discriminate 45 degrees left from 45 degrees right above chance with bilateral stimulation. Three subjects could perform the discrimination above chance with only one ear. However, performance with both ears was significantly better than performance with one ear for two of these latter subjects.

CONCLUSIONS

We conclude that bilateral cochlear implants can provide real advantages, particularly when it is possible to utilize the ear that is away from a noise source, thus taking advantage of the head shadow effect. In addition, localization ability was generally better with two implants than with one.

Successful cochlear implantation in prelingual profound deafness resulting from the common 233delC mutation of the GJB2 gene in the Japanese

OBJECTIVES

Recently, we identified three novel mutations of the GJB2 gene in Japanese families with autosomal-recessive non-syndromic deafness.1 Seven of 11 mutated chromosomes (63.6%) contained a 233delC allele, suggesting that the 233delC mutation is the most common mutation of the GJB2 gene in the Japanese population. After it was recognized that cochlear implantation (CI) is of benefit to children with prelingual deafness, we have had a number of prelingual pediatric CI patients. Because children carrying the homozygous 233delC mutation show bilateral prelingual profound deafness, they could be enrolled in the CI program at Osaka University Graduate School of Medicine. The purposes of this study were 1) to analyze the occurrence of the GJB2 mutations in our 15 prelingual pediatric CI patients in whom the cause of non-syndromic deafness was unknown, and 2) to evaluate the auditory function and postoperative speech perception with CI of those GJB2-related deaf subjects.

STUDY DESIGN

Retrospective analysis.

METHODS

Mutation analysis of the GJB2 gene by direct sequencing was performed with genomic DNA from 15 children born profoundly deaf as a result of unknown causes and implanted with CI. Intraoperative electrically evoked auditory brainstem response (EABR) and intra-/postoperative EAP were measured. The speech perception was evaluated with Infants and Toddlers Meaningful Auditory Integration Scale (IT-MAIS).

RESULTS AND CONCLUSIONS

We identified 4 CI patients (26.7%) out of 15 children carrying the homozygous 233delC mutation. Intra- and postoperative evaluation of the auditory system revealed almost intact cochlear and retrocochlear auditory function in these 4 patients. Postoperative auditory testing indicates that their speech perception had become significantly higher in comparison with that of other prelingual CI patients. These results suggest that prelingual deaf children carrying the homozygous 233delC mutation of the GJB2 gene can benefit from CI.

Use of vocalic information in the identification of /s/ and /sh/ by children with cochlear implants

OBJECTIVE

When a syllable such as "sea" or "she" is spoken, listeners with normal hearing extract evidence of the fricative consonant from both the fricative noise and the following vocalic segment. If the fricative noise is made ambiguous, listeners may still perceive "s" or "sh" categorically, depending on information in the vocalic segment. Do children whose auditory experience comes from electrical stimulation also display this effect, in which a subsequent segment of speech disambiguates an earlier segment?

DESIGN

Unambiguous vowels were appended to ambiguous fricative noises to form tokens of the words "she," "sea," "shoe," and "Sue." A four-choice identification test was undertaken by children with normal hearing (N = 29), prelingually deaf children with the Nucleus Spectra-22 implant system using the SPEAK coding strategy (N = 13), postlingually deafened adults with the same implant system (N = 26), and adults with normal hearing (N = 10). The last group undertook the test before and after the stimuli were processed to simulate the transformations introduced by the SPEAK coding strategy.

RESULTS

All four groups made use of vocalic information. Simulated processing reduced the use made by normal-hearing adults. Implanted subjects made less use than the other groups, with no significant difference between implanted children and implanted adults. The highest levels of use by implanted subjects were within one standard deviation of the mean level displayed when normal-hearing adults listened to processed stimuli. Analyses showed that the SPEAK strategy distorted formant contours in the vocalic segments of the stimuli in ways that are compatible with the errors of identification made by implanted subjects.

CONCLUSIONS

Some children with implants can extract information from a following vowel to disambiguate a preceding fricative noise. The upper limit on this ability may be set by distortions introduced by the implant processor, rather than by the auditory experience of the child.

A model of a nucleus 24 cochlear implant fitting protocol based on the electrically evoked whole nerve action potential

OBJECTIVE

The goal of this study was to model a cochlear implant fitting protocol based on the electrically evoked whole nerve action potential (EAP) measured using the Neural Response Telemetry capabilities of the Nucleus C124M cochlear implant. The model and data were based on the significant correlations found between the EAP threshold and growth function slope and psychophysical threshold and, dynamic range, respectively, in 12 subjects (Franck, Reference Note 3; Franck & Norton, 2001).

DESIGN

Using a retrospective split-half study design, these correlations found between psychophysical mapping levels and EAP data from six of the subjects were used in a model to predict psychophysical mapping levels from EAP data of the other six subjects.

RESULTS

Predicted psychophysical mapping levels from the model of the EAP-based fitting protocol closely approximated measured cochlear implant fitting psychophysics.

CONCLUSIONS

The close approximation of the measured data to the model data indicates the feasibility of the clinical use of an EAP-based cochlear implant fitting protocol. The realization of this model would only require two loudness judgments from the patient, whereas traditional fitting requires 44, and would be fit in a live-voice mode, accounting for across-electrode loudness summation.

Surgical technique for the Nucleus Contour cochlear implant

This paper deals with the Nucleus C124R (CS) (Contour) cochlear Implant: its characteristics, differences compared with the previous generation of devices, the perimodiolar electrode, and the surgical technique used for safe insertion. We also discuss the rationale behind perimodiolar electrodes in general, as well as the results of laboratory studies validating the design and safety of this particular electrode array. The differences in surgical technique between this device and prior Nucleus cochlear implants are as follows: the incision and the size of the well, or recess, for the electronics are smaller; the cochleostomy is larger; the posterior portion is placed in a subpericranial pocket, not tied down, before electrode insertion; and the insertion process itself is quite different, due to the nature of the electrode, its size, shape, and stylet. The technique described is that used by one experienced cochlear implant center, and reflect the authors' practice. Clearly, there are other possible variations on this theme, which may be equally satisfactory in other hands. Most surgeons find this device to be easier to place than previous generations: complications to date have been uncommon.

The results in patients implanted with the nucleus double array cochlear implant: pitch discrimination and auditory performance

OBJECTIVE

In patients with total or surgically inaccessible cochlear obliteration, only a reduced number of active electrodes can be inserted with standard cochlear implants, resulting in below average auditory performance. Therefore, a special implant with two electrode arrays was developed on the basis of the Nucleus 22 cochlear implant, the socalled Double Array. One electrode array with 11 active electrodes is inserted into the basal turn of the cochlea, while the second array with 10 active electrodes is inserted into the second turn. The Double Array is now available on the basis of the more advanced Nucleus 24 with 11 active electrodes on each array and two reference electrodes, one at the case and the second one an additional ball electrode, which is placed under the temporalis muscle. For device description and surgical technique see Lenarz et al. (2001). This paper presents psychophysical data on pitch discrimination and auditory performance of patients implanted with a Double Array on the basis of the Nucleus 22.

STUDY DESIGN

A prospective intra-individual study using a Latin square paradigm was performed in six adult patients with obliterated cochlea who received the Nucleus 22 Double Array. After appropriate fitting and loudness balancing, patients were tested either with the basal, the apical or both electrode arrays. Apart from auditory performance tests including numbers and monosyllable word tests, pitch discrimination was determined with a defined procedure.

RESULTS

When activating each array alone, auditory performance was better with the basal array than with the apical array. Both arrays together showed marked improvement compared with the basal array, indicating an additional effect of the second array. Pitch discrimination was significantly better for the electrodes in the basal turn than in the second turn, indicating differences in electrical excitation of the auditory nerve fibers. Pitch discrimination was positively correlated with auditory performance data.

CONCLUSION

The additional apical array leads to significant improvement in auditory performance in patients with obliterated cochleae by increasing the number of intracochlear electrodes. Despite reduced pitch discrimination, the apical array provides important information for speech recognition. For this reason the Double Array provides a profound advantage for patients with obliterated or surgically inaccessible cochleae.

Speech perception and functional benefit after cochlear implantation: a multicentre survey in Finland

This study was done to survey the effect of cochlear implantation on hearing level, speech perception and listening performance in Finnish-speaking adults. The subjects of the study comprise 67 adults. Pure-tone thresholds (0.125-8 kHz), word recognition and listening performance were studied before and after implantation. After switch-on of the implant, the median values of PTA(0.5-4 kHz) in the sound field were fairly stable across the evaluation period. Three months after switch-on of the implant, the mean word recognition score was 54%. There was clear improvement in the mean word recognition scores over a longer period of time, the mean score being 71% 24 months after switch-on. Six months after switch-on, the majority of subjects (40/48) were able to recognize some speech without speechreading, and 26 of these 48 subjects were able to use the telephone with a known speaker, gaining good functional benefit from the implantation.

The effects of age of cochlear implantation on speech perception outcomes in prelingually deaf children

We have made a retrospective analysis on 70 prelingually deaf children (78% congenital; age range 2-15 years) followed for up to 5 years post-implant during which both closed set speech perception tests (TAC, WIPI) and open set tasks (PBK, GASP) were administered. We used a binary partitioning algorithm to optimally divide our dataset on the basis of age at implantation This technique achieves an optimal split when the heterogeneity of the data is most reduced (maximal drop in deviance). For the closed set speech perception tests (TAC and WIPI) partitioning best divided-out data at age 4.4 years. For the open set tests optimal division was at a higher age of implantation (GASP word, 5.6 years; PBK word, 8.4 years). Using these partitioning values, we have found statistically significant differences between rate of improvement of scores in the younger implanted children compared with those implanted later.