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PubMed2006

Effects of vowel context on the recognition of initial and medial consonants by cochlear implant users.

OBJECTIVE: Scores on consonant-recognition tests are widely used as an index of speech-perception ability in cochlear implant (CI) users. The consonant stimuli in these tests are typically presented in the /alpha/ vowel context, even though consonants in conversational speech occur in many other contexts. For this reason, it would be useful to know whether vowel context has any systematic effect on consonant recognition in this population. The purpose of the present study was to compare consonant recognition for the /alpha, i/, and /u/ vowel contexts for consonants presented in both initial (Cv) and medial (vCv) positions. DESIGN: Twenty adult CI users with one of three different implanted devices underwent consonant-confusion testing. Twelve stimulus conditions that differed according to vowel context (/alpha, i, u/), consonant position (Cv, vCv), and talker gender (male, female) were assessed in each subject. RESULTS: Mean percent-correct consonant-recognition scores were slightly (5 to 8%) higher for the /alpha/ and /u/ vowel contexts than for the /i/ vowel context for both initial and medial consonants. This general pattern was observed for both male and female talkers, for subjects with better and poorer average consonant-recognition performance, and for subjects using low, medium, and high stimulation rates in their speech processors. In contrast to the mean data, many individual subjects demonstrated large effects of vowel context. For 10 of 20 subjects, consonant-recognition scores varied by 15% or more across vowel contexts in one or more stimulus conditions. Similar to the mean data, these differences generally reflected better performance for the /alpha/ and /u/ vowel contexts than for the /i/ vowel context. An analysis of consonant features showed that overall performance was best for the voicing feature, followed by the manner and place features, and that the place feature showed the strongest effect of vowel context. Vowel-context effects were strongest for the six consonants /d, j, n, k, m/, and /l/. For three of these consonants (/j, n, k/), the back vowels /alpha/ and /u/ produced substantially (30 to 35%) higher mean scores than the front vowel /i/. For each of the remaining three consonants, a unique pattern was observed in which a different single vowel produced substantially higher scores than the others. Several additional consonants (/s, g, w, b/, and /d/) showed strong context effects in either the initial consonant or medial consonant position. Overall, voiceless stop, nasal, and glide-liquid consonants showed the strongest effects of vowel context, whereas the voiceless fricative and voiceless affricate consonants were least affected. Consistent with the feature analysis, a qualitative assessment of phoneme errors for the six key consonants indicated that vowel-context effects stem primarily from changes in the number of place-of-articulation errors made in each context. CONCLUSIONS: Vowel context has small but significant effects on consonant-recognition scores for the "average" CI listener, with the back vowels /alpha/ and /u/ producing better performance than the front vowel /i/. In contrast to the average results, however, the effects of vowel context are sizable in some individual subjects. This suggests that it may be beneficial to assess consonant recognition using two vowels, such as /alpha/ and /i/, which produce better and poorer performance, respectively. The present results underscore previous findings that poor transmission of spectral speech cues limits consonant-recognition performance in CI users. Spectral cue transmission may be hindered not only by poor spectral resolution in these listeners but also by the brief duration and dynamic nature of consonant place-of-articulation cues.

Acoustic Stimulation↗

PubMed1993

Electrode position, repetition rate, and speech perception by early- and late-deafened cochlear implant patients.

Psychophysical and speech perception studies were conducted on eight patients using the 22-electrode cochlear implant manufactured by Cochlear Pty. Ltd. Four early-deafened patients became deafened at 1-3 years of age and were implanted at 5-14 years of age. Four late-deafened (postlingual adult) patients became deafened at 38-47 years of age and were implanted at 42-68 years of age. Psychophysical studies measured the discrimination of trajectories with time-varying electrode positions and repetition rates. Speech perception studies measured performance using two speech coding strategies: a multi-electrode strategy which coded the first and second formant frequencies, the amplitudes of the two formants, and the fundamental frequency; and a single-electrode strategy which coded the amplitudes of the first and second formants, and the fundamental frequency. In general, the four late-deafened patients and one early-deafened patient were more successful than the other three early-deafened patients in the discrimination of electrode position trajectories and in speech perception using the multi-electrode strategy. Three of the four late-deafened patients were more successful than the early-deafened patients in the discrimination of repetition rate trajectories. Speech perception performance in the single-electrode strategy was closely related to performance in repetition rate discrimination. The improvement in speech perception performance from the single-electrode to multi-electrode strategy was consistent with successful performance in electrode discrimination.

Acoustic Stimulation↗

PubMed1990

[Cochlear Implant Mini-System 22 for the management of deaf preschool children].

The long-term reliability and the overall good results achieved with cochlear implants in adults have led us to consider whether this method could also be applied in small children. This though was supported by the work of House, who has been providing children with cochlear implants for many years, although using a monochannel device with only one electrode, which is inserted only a few millimetres into the scala tympani. Our considerations were also prompted by technical progress which has resulted in the so-called Mini System 22. In this system, the implant is only 6 mm thick with a speech processor of a mere 9 x 6 x 1.9 cm and weighs not more than 100 g. From the point of view of the surgical technique, small children do not present any specific difficulties, except for the necessity of fixing the array of electrodes as closely as possible to the cochlea, in order to avoid its slipping out of the cochlea during skull growth. Positive results with single reimplantations indicate that such patients will also be able to benefit from technical progress in future decades. To differentiate between inner ear and nerve deafness the promontory test has to be replaced by electrocochleography. This indicates a neural genesis of the hearing impairment in cases of cochlear microphonics of more than 50-60 nHL and possibly even a summation potential can be recorded. Additionally, we consider it mandatory to use objective parameters as a basis for the first tune-up of the speech processor.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiometry, Evoked Response↗

PubMed2005

Pharmacological enhancement of aural habilitation in adult cochlear implant users.

OBJECTIVE: The purpose of this report was to examine the preliminary data collected under a larger on-going feasibility study conducted with cochlear implant patients exploring the potential benefit of pharmacologically-enhanced aural rehabilitation therapy as a means of increasing speech tracking skills. DESIGN: Eight adult cochlear implant participants participated in a randomized, double-blind study and received either 10 mg d-amphetamine (Treatment group, N = 4) or a placebo (Placebo group, N = 4) 60 minutes prior to a 1.5 hour intensive aural rehabilitation session occurring twice a week for two months. Treatment consisted of a multi-step rehabilitation program individualized for each participant to develop auditory-only speech tracking skills. Prior to and at the conclusion of the therapy sessions, SPECT rCBF imaging and speech tracking assessments were conducted. RESULTS: Speech tracking scores of the placebo and treatment groups were similar before the aural habilitation intervention. In the placebo group, speech tracking performance increased 13.5% for visual plus auditory and auditory only presentations as a function of aural habilitation alone. The 10 mg d-amphetamine-facilitated program resulted in minimal increases in visual plus auditory tracking scores (2%) but led to a 43% increase for auditory-only speech tracking. Regional cerebral blood flow measures indicated no substantial improvement of brain activation in the placebo group while both the extent and magnitude of primary and associative auditory cortex activations increased significantly with the pharmacologically enhanced treatment program. CONCLUSIONS: These data support previous studies indicating an accelerated acquisition of speech and language abilities in stroke patients receiving traditional speech therapy in combination with d-amphetamine. Data, however, are preliminary and further study is warranted.

Adult↗

PubMed1989

[Results of rehabilitation of patients after cochlear implantation of a single-channel extracochlear neuroprosthesis manufactured in Czechoslovakia].

The authors present an account of the results of rehabilitation of the first three subjects after cochlear implantation of a Czechoslovak single-channel neuroprosthesis. The results of rehabilitation were evaluated by means of specially designed videotests and audiotests to make the results comparable with results of neuroprostheses implanted abroad. Based on these tests--in particular MSD--they reached the unequivocal conclusion that the results of cochlear implantation of the Czechoslovak extracochlear neuroprosthesis, as far as rehabilitation is concerned, compare favourably with results achieved by other neuroprosthesis of this type. In all three patients the neuroprosthesis mediates to the patients information on the presence of sound, in many instances it makes identification of this sound possible. In combination with lip-reading the patients are able without major problems to communicate with the environment. Resocialization of the operated patients was achieved.

Adult↗

PubMed1993

Loudness balance between acoustic and electric stimulation by a patient with a multichannel cochlear implant.

Estimates of loudness balance were obtained for acoustically and electrically presented 250 Hz sine signals from a patient who uses the Ineraid multichannel cochlear implant. Acoustic and electric loudness matching was possible because the patient evidenced a 25 dB HL threshold at 250 Hz in his nonimplanted ear. The level of the electrical stimulus in microamperes required for a balance of loudness grew linearly with equal increments in decibels for the acoustic stimulus. These data, in concert with the very limited data from previous studies, provide a rationale for using a logarithmic transformation of acoustic to electric intensity in signal processors for cochlear implants.

Acoustic Stimulation↗

PubMed2000

[Hearing and speech discrimination scores of prelingually deaf children with cochlear implants].

The goal of this study is to report mean values of speech perception performance in prelingually deaf children who received a Combi 40/40+ cochlear implant. Thirty-one patients were included in the study. The time span ranged over 3 years, during which time the Evaluation of Auditory Responses to Speech (EARS) test battery was used in the children. The EARS battery contains 4 measures of closed-set speech perception and 3 open-set tests. The mean test results exhibited steady improvement in all parts of the EARS test battery, even up to 3 years post-implantation. The mean preoperative scores were 0.3%, increasing to 92.3% at 36 months post-implantation for the best children. Results for the closed-set testing measures were most encouraging, with some children reaching fairly high levels of speech perception and achieving scores as high as 98.7% at the 36-month evaluation. The congenitally and prelingually deaf children in our study showed continuous improvement in both closed and open set speech perception following cochlear implantation, although individual variations in performance were noted.

Age Factors↗

PubMed1995

CT of postmeningitic deafness: observations and predictive value for cochlear implants in children.

PURPOSE: To demonstrate CT abnormalities encountered in children with postmeningitic deafness and to assess the value of CT in the prediction of cochlear implantation difficulties. METHODS: Thirteen children with postmeningitic deafness were evaluated with high-resolution, thin-section CT. CT findings were correlated with surgical anatomy at the time of cochlear implantation, with particular regard to the prediction of implant success. RESULTS: CT findings included normal scans (3 of 13, 23.1%), cochlear stenosis (5 of 13, 37.7%), cochlear fibroossific change (1 of 13, 7.7%), cochlear ossification (4 of 13, 30.8%), and osseous hypertrophy at the round window niche (4 of 13, 30.8%). Nine of 10 patients with abnormal findings had incomplete or difficult implantations (90%); 7 (88.8%) of these 9 received limited electrode insertions. CONCLUSION: Attention to subtle otological abnormalities on thin-section CT is helpful in the prediction of early success or failure of implantation in children with postmeningitic deafness. Those with CT abnormalities had a 90% risk of incomplete or difficult insertions with a 70% chance of limited electrode insertion.

Adolescent↗

PubMed2002

Successful cochlear implantation in a child after recovery from a head and neck malignancy: a case report.

We present the case of a successful pediatric cochlear implantation that was carried out following bilateral perilingual deafness caused by meningitis during the treatment of a childhood malignant tumor. A rhabdomyosarcoma localized in the frontobasal area was removed from the child at the age of 2 years. He then received 11 months of postoperative cytostatic treatment. A purulent meningitis developed at the end of the chemotherapy, resulting in a major-grade, bilateral sensorineural hearing loss (practically a perilingual deafness). After 6 tumor-free years and a meticulous preoperative assessment, a Nucleus 24 M cochlear implant was successfully implanted in the child's left ear. Two years after the operation, the child shows excellent hearing results and moderate speech development.

Antineoplastic Agents↗

PubMedDate not supplied

Deafness-induced changes in the auditory pathway: implications for cochlear implants.

A profound sensorineural hearing loss induces significant pathological and atrophic changes within the cochlea and central auditory pathway. We describe these deafness-induced morphological and functional changes following controlled lesions of the cochlea in experimental animals. Such changes are generally consistent with the limited number of reports describing deafness-induced changes observed in human material. The implications of these pathophysiological changes within the auditory pathway on cochlear implant function are discussed. Finally, the plastic response of the deafened auditory system to electrical stimulation of the auditory nerve is reviewed in light of the clinical implications for cochlear implant recipients.

Animals↗

PubMed2003

Effects of presentation level on phoneme and sentence recognition in quiet by cochlear implant listeners.

OBJECTIVE: The objectives of this study were to characterize the effects of presentation level on speech recognition in quiet by cochlear implant users with the Nucleus 22 SPEAK and Clarion v1.2 CIS speech-processing strategies, and to relate speech recognition at low presentation levels to stimulus audibility as measured by sound field thresholds. It was hypothesized that speech recognition performance in both Nucleus SPEAK and Clarion CIS participants would decrease as presentation level was decreased below 50 to 60 dBA, due to audibility limitations. However, it was expected that such level effects would be less severe in CIS participants than in SPEAK participants because the Clarion v1.2 device encodes a wider acoustic dynamic range (up to 60 dB) than the Nucleus 22 device (30 dB). DESIGN: Performance-intensity (P-I) functions for vowels, consonants and sentences in quiet were obtained from each participant. P-I functions incorporated speech levels of 70, 60, 50, 40 and 30 dBA. Subjects used their clinical speech processor maps and adjusted the loudness (volume/sensitivity) controls on their processors so that speech presented at 60 dBA was comfortably loud. Maps were created using default clinical procedures and were not adjusted to optimize sound field thresholds. Sound field thresholds and dynamic ranges were measured for warbled pure tones with frequencies of 250 to 6000 Hz. RESULTS: Consonant and sentence recognition showed strong level effects for both SPEAK and CIS participants, with performance decreasing substantially at levels below 50 dBA in most individuals. Vowel recognition showed weaker level effects. For all three speech materials, SPEAK and CIS participants demonstrated similar mean performance at 70 dBA; however, SPEAK participants showed larger reductions in performance than CIS participants with decreasing level. Sound field thresholds were more sensitive for CIS participants than for SPEAK participants, supporting the hypothesis that performance differences were related to audibility. CONCLUSIONS: Cochlear implant listeners are unable to maintain good speech recognition at low presentation levels due to reduced stimulus audibility, and this may significantly limit their ability to communicate in daily life. It is likely that audibility differences between SPEAK and CIS participants in the present study can be attributed at least partly to differences in the acoustic dynamic range used by the respective processors. However, several additional factors may have contributed to differences in audibility and perception of soft speech among individual listeners with both devices. These include the minimum and maximum electrical stimulation levels specified in participants' maps and the speech processor sensitivity setting used for testing.

Adult↗

PubMed1999

Cerebral auditory plasticity and cochlear implants.

Previous animal research and clinical experiences in humans suggest the existence of an auditory critical period in language acquisition. We review the literature and present the changes within the cochlear nuclei in bilaterally deafferentated adult non-human primates. We also present and analyse the results of 98 prelingually deaf children and teenagers who underwent a cochlear implantation at the University of Navarra. Patients received a Nucleus 22 or 24 multichannel cochlear implant (CI). They were grouped in five categories according to their age at surgery. Performance is compared with a control group of 58 postlinguals. Only early-implanted prelingual children (before 6 years of age) achieved a complete open-set speech recognition, even with better performance than postlinguals. These results clearly demonstrate the existence of a period of high neural auditory plasticity within the first 6 years of life. The introduction of auditory stimulation with a CI can not restore the loss of neural plasticity out of this period. Prelingual children under 6 years of age should receive a CI as soon as there is a reliable diagnosis of bilateral sensorineural hearing loss.

Adolescent↗

PubMed1991

Late cortical auditory potentials evoked by electrostimulation in deaf and cochlear implant patients.

Deaf or residually hearing patients without sufficient auditory communication by conventional hearing aids are candidates for the implantation of a cochlear prosthesis. In addition to objective audiometry (electrophysiological evaluation and assessment of the degree and type of hearing loss), preoperative electrostimulation tests should be performed. In so doing, it is reasonable to employ late cortical potentials for preoperative patient selection as well as for postoperative follow-ups. In contrast to early potentials (such as, brain stem evoked potentials), late cortical potentials offer technical, physiological, medical and psychological advantages. This approach to testing has been used successfully in 70 patients (including children over the age of 3 years).

Adult↗

PubMed1994

The Mayo Clinic experience with the cochlear implant.

The implantation of a cochlear electronic prosthetic device is an acceptable means of improving the communication ability of pre- and postlingually deafened children and adults. A significant number of patients in this series are in the senior citizen age group. It has been beneficial in improving communication ability in selected profoundly deafened individuals. There has been a significant improvement in the cochlear electronic prosthetic device since the initial report of Djourno in 1957.

Adult↗

PubMed1997

Cochlear implantation after bacterial meningitis: the dangers of delay.

A case is described of a child of 2.6 years who developed total deafness after acute bacterial meningitis. Rapid obliteration of the cochleas due to osteoneogenesis led to limited cochlear implantation. The case is made for fast tracking these children to cochlear implant teams before neoossification becomes established.

Acute Disease↗

PubMed2002

Cognitive processing in children using cochlear implants: the relationship between visual memory, attention, and executive functions and developing language skills.

We performed this study to determine whether children using a cochlear implant performed differently from age- and gender-matched hearing aid users on 8 neuropsychological measures of visual memory, attention, and executive functioning. The study also examined whether differences in cognitive skills could account for some of the observed variance in speech perception, vocabulary, and language abilities of hearing-impaired children. In contrast to previous studies, our results revealed no significant cognitive differences between children who use a cochlear implant and children who use hearing aids. Partial correlation analysis indicated that the children's visual memory skills, ie, their recognition memory, delayed recall, and paired associative learning memory skills, correlated significantly with their language skills. When examined at a significance level of .01, attention and executive functioning skills did not relate to the children's developing speech perception, vocabulary, or language skills. The results suggested that differences in visual memory skills may account for some of the variance seen in the language abilities of children using implants and children using hearing aids.

Adolescent↗

PubMed1991

Cochlear implantation of totally deaf ears. Histologic evaluation of candidacy.

Successful cochlear implantation depends on the presence of stimulatable neural elements, which are believed to be the spiral ganglion, neurons, or their axons. We examined the 1,152 temporal bones in our laboratory to determine how many with a total sensorineural hearing loss would be implantable. We defined implantable as having 3,500 neurons or more, as determined by successful implant stimulation in two ears from our collection with less than 3,500 neurons. Of 46 bones with deafness, 37 had 3,500 neurons or more and would be considered implant candidates. The types of deafness in the potentially implantable ears and in ears with sufficient neural elements will be discussed.

Cochlear Implants↗

PubMed2001

Is cochlear implantation possible after acoustic tumor removal?

HYPOTHESIS: This study aimed to assess the possibility of hearing restoration after acoustic tumor removal. BACKGROUND: Hearing restoration surgery may be indicated after surgery of bilateral acoustic tumors or surgery of acoustic tumor in the only hearing ear. The choice is between cochlear implantation and brainstem implantation. METHODS: From the temporal bone collection at the House Ear Institute, Los Angeles, the author histologically examined eight temporal bones from seven patients who had undergone acoustic tumor removal during their lifetime. Special emphasis was put on examining the patency of the cochlear turns and on survival of the spiral ganglion cells and cochlear nerve. RESULTS: This study showed that after translabyrinthine acoustic tumor removal, there is progressive osteoneogenesis of the cochlea associated with almost complete degeneration of the spiral ganglion cells and cochlear nerve. Similar findings were noticed after middle fossa removal of acoustic tumor with unsuccessful hearing preservation. CONCLUSIONS: The histologic changes described in the cochlea and cochlear nerve represent the effects of ischemia resulting from inadvertent cutting of the blood supply during acoustic tumor removal. It is possible to do cochlear implantation after acoustic tumor removal provided that the result of promontory electrical stimulation test is positive (the cochlear nerve is intact) and that implantation is done at the time of acoustic tumor removal or shortly thereafter, before cochlear ossification is complete.

Cochlea↗