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PubMed2004

Optimizing frequency-to-electrode allocation in cochlear implants.

This study tested the hypothesis that speech perception of cochlear implant users could be improved by increasing the number of electrodes allocated to frequencies below 2.6 kHz, with correspondingly fewer electrodes allocated above this point. Eight users of the Nucleus CI22 implant participated and wore experimental maps in which the widths of the analysis filters were altered to provide either two or three extra low-frequency channels. Speech perception was tested following periods of take-home experience. Information transmission analysis of vowel and consonant confusions appear to support our hypothesis, showing that vowel first formant information was significantly better perceived with the experimental map and that consonant information was not significantly different. The results of CNC word testing appear to contradict this result, showing that the experimental map degraded both vowel and consonant perception. Overall, the experimental map had a small and variable effect on speech perception. These results do not support our hypothesis and indicate that further research is needed to investigate the possible effects of narrowing the filter bandwidth in low frequencies, as done in this experiment.

Aged↗

PubMed2006

Cortical activity at rest predicts cochlear implantation outcome.

The functional status of central neural pathways, in particular their susceptibility to plasticity and functional reorganization, may influence speech performance of deaf cochlear implant users. In this paper, we sought to determine how brain metabolic activity measured before implantation relates to cochlear implantation outcome, that is, speech perception. In 22 prelingually deaf children between 1 and 11 years, we correlated preoperative glucose metabolism as measured by F-18 fluorodeoxyglucose positron emission tomography with individual speech perception performance assessed 3 years after implantation, while factoring out the confounding effect of age at implantation. Whereas age at implantation was positively correlated with increased activity in the right superior temporal gyrus, speech scores were selectively associated with enhanced metabolic activity in the left prefrontal cortex and decreased metabolic activity in right Heschl's gyrus and in the posterior superior temporal sulcus. These results reinforce the notion that implantation should be performed as early as possible to prevent cross-modal takeover of auditory regions and suggest that rehabilitation strategies may be more efficient if they capitalize on general cognitive functions instead of only targeting specialized circuits dedicated to auditory and audiovisual pattern recognition.

Auditory Cortex↗

PubMed2005

Effect of age at cochlear implantation on open-set word recognition in Mandarin speaking deaf children.

OBJECTIVE: The purpose of this study was to determine whether age at cochlear implantation influences open-set speech perception in children after long-term use of the implant device. METHOD: Twenty-eight congenitally deafened children, receiving implants of Nucleus CI24M devices, were divided into two groups: (1) CI < 3: those who received implants before 3 years of age and (2) CI > 3: those who received implants after 3 years of age. We compared open-set speech perception in CI < 3 and CI > 3 after 4-5 years of device use. Speech perception tests were conducted using the Mandarin Lexical Neighborhood Test (M-LNT). Unpaired t-test was applied for statistical analysis, and p < 0.05 was considered significant. RESULTS: In CI < 3, the average of percent correct was 80.0 +/- 8.8 and 70.5 +/- 9.2% on, respectively, the easy and hard versions of the M-LNT. By contrast, in CI > 3, the average percent correct was 62.5 +/- 19.9 and 59.1 +/- 15.2%, respectively. Regardless of the M-LNT version used, CI < 3 performed significantly better than CI > 3 (easy, p = 0.005 versus hard, p = 0.022). CONCLUSION: The present investigation demonstrated that age at implantation influences open-set speech perception of cochlear implanted children 4-5 years after device connection. Implantation before 3 years of age promotes the development of open-set speech perception abilities in congenitally deafened children.

Age Factors↗

PubMed1987

The University of Toronto cochlear implant study: a clinical overview.

The process of patient selection for a cochlear implant varies significantly from center to center. The University of Toronto Cochlear Implant Study Group has adopted a protocol which is unique in this regard. This overview highlights our selection process, details aspects of temporary electrode insertion and describes clinical findings considered to be of relevance.

Audiometry, Evoked Response↗

PubMed1998

Tinnitus in Cochlear Implant Users: The Freiburg Experience.

Cochlear implantation is a well-accepted method of aural rehabilitation in deaf or severely hearing-impaired adults and children. A majority of patients not only suffer from hearing impairment but from tinnitus. The high rate of preoperative tinnitus in adults (68.1%) stands in contrast to assumed lower rates in children. Unknown are such factors as how tinnitus develops in children, how they realize what tinnitus is, and whether the mechanism of development of tinnitus differs from that in adults, respectively. Electrical stimulation of the auditory pathway is followed by loss, or at least reduction, of tinnitus in most cases (75%). Also, the insertional trauma alone is able to stop tinnitus in some patients. Attention must be paid to the low risk of developing tinnitus postoperatively. No reports are available regarding tinnitus in children. Though younger children may not be able to report, some adolescent patients report preoperative or postoperative tinnitus (or both) that is reduced by electrical stimulation at the rates seen in adults. Further investigations are needed to define the mechanism of tinnitus development in children and to define optimal stimulation modes and rates for tinnitus reduction with best auditory performance.

Journal Article↗

PubMed2006

Cochlear implantation in patients with neurofibromatosis type 2 and bilateral vestibular schwannoma.

OBJECTIVE: To investigate the results of cochlear implantation in patients with neurofibromatosis Type 2 (NF2) and bilateral vestibular schwannoma. STUDY DESIGN: Retrospective case review. SETTING: Three academic tertiary referral centers. PATIENTS: Seven patients with NF2 and bilateral vestibular schwannoma who lost hearing in at least one ear after treatment of their tumor (surgery or radiation therapy). INTERVENTION: Cochlear implantation after treatment of their vestibular schwannoma. MAIN OUTCOME MEASURE: Postimplantation audiometric scores (pure-tone average thresholds, consonant-nucleus-consonant (CNC) words/phonemes, Central Institute for the Deaf (CID) sentences, Hearing in Noise Test (HINT) quiet/noise, and Monosyllable, Trochee, Spondee (MTS) recognition/category tests), patient satisfaction, and device use patterns. RESULTS: The average age at implantation was 40 years (range, 16-57 yr). Follow-up ranged from 6 to 88 months after implantation. Three patients were implanted with residual useful hearing in the contralateral ear, whereas four patients had no hearing in the contralateral ear. Hearing loss was due to surgical excision of tumor (n=5) or gamma-knife radiotherapy (n=2). Postactivation pure-tone average thresholds in the implanted ear ranged from 30 to 55 dB (average, 32.5 dB), although speech reception testing varied considerably among subjects. Despite this variability, all patients continue to use the device on a daily basis. CONCLUSION: In selected cases of deafness in patients with NF2 where there has been anatomic preservation of the auditory nerve after acoustic neuroma resection or radiation therapy, cochlear implantation may offer some improvement in communication skills, including the possibility of open-set speech communication in some patients. These results compare favorably to the auditory brainstem implant offering an alternative for hearing rehabilitation in patients with NF2.

Adolescent↗

PubMed2006

Effects of programming threshold and maplaw settings on acoustic thresholds and speech discrimination with the MED-EL COMBI 40+ cochlear implant.

OBJECTIVES: The principal task in the programming of a cochlear implant (CI) speech processor is the setting of the electrical dynamic range (output) for each electrode, to ensure that a comfortable loudness percept is obtained for a range of input levels. This typically involves separate psychophysical measurement of electrical threshold ([theta] e) and upper tolerance levels using short current bursts generated by the fitting software. Anecdotal clinical experience and some experimental studies suggest that the measurement of [theta]e is relatively unimportant and that the setting of upper tolerance limits is more critical for processor programming. The present study aims to test this hypothesis and examines in detail how acoustic thresholds and speech recognition are affected by setting of the lower limit of the output ("Programming threshold" or "PT") to understand better the influence of this parameter and how it interacts with certain other programming parameters. DESIGN: Test programs (maps) were generated with PT set to artificially high and low values and tested on users of the MED-EL COMBI 40+ CI system. Acoustic thresholds and speech recognition scores (sentence tests) were measured for each of the test maps. Acoustic thresholds were also measured using maps with a range of output compression functions ("maplaws"). In addition, subjective reports were recorded regarding the presence of "background threshold stimulation" which is occasionally reported by CI users if PT is set to relatively high values when using the CIS strategy. RESULTS: Manipulation of PT was found to have very little effect. Setting PT to minimum produced a mean 5 dB (S.D. = 6.25) increase in acoustic thresholds, relative to thresholds with PT set normally, and had no statistically significant effect on speech recognition scores on a sentence test. On the other hand, maplaw setting was found to have a significant effect on acoustic thresholds (raised as maplaw is made more linear), which provides some theoretical explanation as to why PT has little effect when using the default maplaw of c = 500. Subjective reports of background threshold stimulation showed that most users could perceive a relatively loud auditory percept, in the absence of microphone input, when PT was set to double the behaviorally measured electrical thresholds ([theta]e), but that this produced little intrusion when microphone input was present. CONCLUSIONS: The results of these investigations have direct clinical relevance, showing that setting of PT is indeed relatively unimportant in terms of speech discrimination, but that it is worth ensuring that PT is not set excessively high, as this can produce distracting background stimulation. Indeed, it may even be set to minimum values without deleterious effect.

Acoustic Stimulation↗

PubMed1993

Psychological assessment of multi-channel cochlear implant patients.

The psychological effects of profound or total acquired deafness can impair cognitive and interpersonal functioning. A cochlear implant has important psychological implications for individuals and usually has a major impact on the lives of implantees and their families. Psychological assessment and monitoring has formed an integral part of the multi-channel cochlear implant programme at Manchester and contributes to team decisions made about the suitability of patients for implant and subsequent progress of implantees. In this paper the major reasons for carrying out psychological assessment on prospective implantees and for monitoring psychological status of implantees are discussed. The main assessment techniques used at Manchester are described. Group findings from the initial assessments of the first 30 cochlear implant patients (including three deaf-blind subjects) are reported.

Adolescent↗

PubMed2000

Effects of dynamic range and amplitude mapping on phoneme recognition in Nucleus-22 cochlear implant users.

OBJECTIVE: To determine the consequences for phoneme recognition of errors in setting threshold and loudness levels in cochlear implant listeners using a 4-channel continuous interleaved sampling (CIS) speech processor. DESIGN: Three Nucleus-22 cochlear implant listeners, who normally used the SPEAK speech processing strategy participated in this study. An experimental 4-channel CIS speech processor was implemented in each listener as follows. Speech signals were band-pass filtered into four broad frequency bands and the temporal envelope of the signal in each band was extracted by half-wave rectification and low-pass filtering. A power function was used to convert the extracted acoustic amplitudes to electric currents. The electric currents were dependent on the exponent of the mapping power function and the electrode dynamic range, which was determined by the minimum and maximum stimulation levels. In the baseline condition, the minimum and maximum stimulation levels were defined as the psychophysically measured threshold level (T-level) and maximum comfortable level (C-level). In the experimental conditions, the maximum stimulation levels were fixed at the C-level and the dynamic range (in dB) was changed by varying the minimum stimulation levels on all electrodes. This manipulation simulates the effect of an erroneous measurement of the T-level. Phoneme recognition was obtained as the dynamic range of electrodes was changed from 1 dB to 20 dB and as the exponent of the power-law amplitude mapping function was changed from 0.1 to 0.4. RESULTS: For each mapping condition, the electric dynamic range had a significant, but weak effect on vowel and consonant recognition. For a strong compression (p = 0.1), best vowel and consonant scores were obtained with a large dynamic range (12 dB). When the exponent of the mapping function was changed to 0.2 and 0.4, the dynamic range producing the highest scores decreased to 6 dB and 3 dB, respectively. CONCLUSIONS: Phoneme recognition with a 4-channel CIS strategy was only mildly affected by large changes in both electric threshold and loudness mapping. Errors in threshold by a factor of 2 (6 dB) and in the loudness mapping exponent by a factor of 2 were required to produce a significant decrease in performance. In these extreme conditions, the effect of the electric dynamic range on phoneme recognition could be due to two independent factors: abnormal loudness growth and a reduction in the number of discriminable intensity steps. The decrease in performance caused by a reduced electric dynamic range can be compensated by a more expansive power-law mapping function, as long as the number of discriminable intensity steps is moderately large (e.g., >8).

Acoustic Stimulation↗

PubMed2001

Histopathology of cochlear implants in humans.

The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.

Aged↗

PubMed1985

Auditory capabilities of single-channel cochlear implant patients. Etiologic considerations.

The clinical audiometric test results from 53 postlingually deafened adults using the House single-channel cochlear implant were analyzed according to cause of deafness (otosclerosis, ototoxic drugs, meningitis, and trauma). With the exception of one measure, the routine clinical tests did not show a relationship between cause of deafness and performance with the cochlear implant. These findings suggest that, clinically, the single-channel cochlear implant is a viable prosthesis for patients with a wide variety of causes of deafness.

Adolescent↗

PubMed1998

Speech recognition performance of older children with cochlear implants.

HYPOTHESIS: The primary purpose of this study was to determine if children, > or =5 years old, with onset of deafness before the acquisition of spoken language (i.e., prelingually deafened) derived more benefit from multichannel cochlear implants than from conventional hearing aids. It was hypothesized that children who used oral communication (speech plus listening) would demonstrate higher levels of performance after implantation than children who used total communication (English sign system plus speech and listening). BACKGROUND: Previous research suggests that prelingually deafened children given implants at an older age derive limited benefit from these devices. Changes in candidacy criteria and advances in technology, however, may make cochlear implants a more viable treatment option for this group of patients. METHODS: A repeated-measures design was to used to compare patients' preoperative performance with hearing aids to postoperative performance with the CLARION cochlear implant after 3 and 6 months of device use. Pre- and postoperative performance were analyzed separately for children who used oral and total communication. RESULTS: Both groups of children (oral and total communication) demonstrated significant postoperative improvement on all outcome measures over time. Postoperative scores of the children who used oral communication were significantly higher than those of the children who used total communication on four of the five outcome measures. CONCLUSIONS: Prelingually deafened children who do not receive cochlear implants until > or =5 years of age derive significant benefit from current implant devices compared with that obtained with conventional hearing aids. The greatest benefit is derived by children who use oral communication, with much more limited benefit demonstrated by children who use total communication.

Acoustic Stimulation↗

PubMedDate not supplied

Cochlear implants in children.

In recent years, the House single-electrode cochlear implant has proven to be a clinically feasible prosthesis for profoundly deaf adults. Based on these findings, the decision was made to begin implanting those children who could not benefit from hearing aids. As of August 1982, 23 profoundly deaf children (ranging in age from 3.4 to 17.5 yrs) have received the cochlear implant. The majority were deafened by meningitis. Results to date indicate that children demonstrate sound field thresholds and receive timing/intensity information comparable to that of adult implant patients. Results have been extremely encouraging, but only long-term experience will determine the ultimate benefit of the implant in children.

Adolescent↗

PubMed2004

Cochlear implant speech recognition with speech maskers.

Speech recognition performance was measured in normal-hearing and cochlear-implant listeners with maskers consisting of either steady-state speech-spectrum-shaped noise or a competing sentence. Target sentences from a male talker were presented in the presence of one of three competing talkers (same male, different male, or female) or speech-spectrum-shaped noise generated from this talker at several target-to-masker ratios. For the normal-hearing listeners, target-masker combinations were processed through a noise-excited vocoder designed to simulate a cochlear implant. With unprocessed stimuli, a normal-hearing control group maintained high levels of intelligibility down to target-to-masker ratios as low as 0 dB and showed a release from masking, producing better performance with single-talker maskers than with steady-state noise. In contrast, no masking release was observed in either implant or normal-hearing subjects listening through an implant simulation. The performance of the simulation and implant groups did not improve when the single-talker masker was a different talker compared to the same talker as the target speech, as was found in the normal-hearing control. These results are interpreted as evidence for a significant role of informational masking and modulation interference in cochlear implant speech recognition with fluctuating maskers. This informational masking may originate from increased target-masker similarity when spectral resolution is reduced.

Adult↗

PubMed1987

The University of Melbourne--nucleus multi-electrode cochlear implant.

To summarize, our preliminary results indicate that some prelingually deaf patients may get worthwhile help from a multiple-electrode cochlear implant which extracts formants. They can understand words and running speech better when using the cochlear implant with lip-reading compared to lip-reading alone. It has been encouraging that these improvements can occur in young adults and teenagers. It has also been encouraging that some can recognize place pitch as well as rate pitch. There are, however, considerable variations in performance and this may be due to the following factors: whether they have had some hearing after birth, the method of education used, the motivation of the patient and age at implantation. In conclusion it is important to emphasize that deaf children are severely disadvantaged however good their teacher of the deaf. Research on cochlear implants offers hope for profoundly-totally deaf children. These developments will not replace the caring, competent educators but complement their skills. There is also a greater need than ever for an interdisciplinary approach to these children.

Animals↗

PubMed2004

New method of using reconstructed images for assessment of patency of intracochlear spaces for cochlear implant candidates.

OBJECTIVE/HYPOTHESIS: A new method of reconstruction using multidetector-row helical computed tomography (MDCT) was applied for assessment of cochlear patency in cochlear implantation candidates. STUDY DESIGN: Descriptive study comparing radiologic and surgical findings in eight radiologically normal cochleas and four abnormal cases. METHODS: In unusual cases including cochlear ossification and misinsertion of electrodes, intracochlear space was evaluated on two types of reconstructed images: the "basal turn plane" that was vertical to the modiolus and contained whole basal turn was effective in the assessment of the lining of the inner bony wall of the otic capsule; "cochlear cross plane" images allowed evaluation of the patency of the intracochlear space and the location of inserted electrodes at the sections vertical to the direction of insertion of the electrodes. RESULTS: Preoperative evaluation was useful for predicting possible problems in electrode insertion and therefore helped in decision-making in regards to surgical strategies, especially in candidates with a high probability of cochlear ossification such as those with meningitis and otosclerosis. Furthermore, the new reconstruction method also provided useful information on the position of the cochlear implant electrodes after surgery. CONCLUSIONS: These unusual cases demonstrated that preoperative MDCT evaluation by our reconstruction method was useful for predicting possible problems in electrode insertion and decision-making in regards to surgical strategies, especially in cochlear implantation candidates with a high probability of cochlear stenosis.

Adolescent↗

PubMed2005

Epidural hematoma after cochlear implantation in a 2.5-year-old boy.

OBJECTIVE: Report a case of an epidural hematoma after cochlear implantation in a 2.5-year-old boy, the diagnostic and therapeutical emergency management, as well as the postinterventional course and rehabilitation of the child. STUDY DESIGN: Retrospective case review. PATIENT: Two and a half-year-old boy, suffering from early onset, profound sensorineural hearing loss had been diagnosed at an age of 1.5 years, which had been more severe on the right side initially, but had progressed to bilateral deafness. INTERVENTION AND COMPLICATION: Cochlear implantation on the left side, followed up by an extensive epidural hematoma, causing intracranial compression with a midline shift of 15 mm to the right side. This initial complication was followed up by arterial infarction not only of the middle but also the posterior as well as the anterior cerebral artery, most likely caused by incarceration through the tentorium. RESULTS: After immediate neurosurgical intervention and intensive care treatment including low-dose anticoagulation and high doses of corticosteroids, the child recuperated completely within 3 weeks without any remaining neurologic deficits. CONCLUSION: In cochlear implantation, especially if placement of the implant housing is associated with considerable bone work, epidural hematoma has to be considered as an extremely rare, but life-threatening, complication.

Child, Preschool↗

PubMed1989

Cochlear implant indications.

Many centers are investigating the safety and efficacy of cochlear implants in adults and children. In the United States, the Food and Drug Administration (FDA) has monitored these investigations, recently approving two devices for general use in adults. In general, appropriate implant candidates have a bilateral, profound to total sensorineural hearing loss, are unable to benefit from conventional hearing aids, are in good physical and mental health, and have the motivation and patience to complete a rehabilitation program. The patient likely to receive most benefit from a cochlear implant is one who acquires profound deafness after developing verbal language skills and is implanted within a few years of the onset of deafness.

Cochlear Implants↗