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At least 19 recordsLinked to original sources

PubMed1997

[Cochlear implants].

Cochlear implants aim at the rehabilitation of profound bilateral deafness. The cochlear implant is a prosthesis made out of surgically implanted cochlear electrodes connected to an external vocal processor. The external acoustic signals are converted into electrical signals coded by the vocal processor. They are then sent out, by a transcutaneous mode, to an internal receptor. This receptor transmits the information to the intracochlear electrodes. Initially, the cochlear implantation was recommended to patients totally deaf following a trauma, a degenerative disease of the inner ear, a meningitis or the use of ototoxic drugs. These patients could not gain from conventional hearing aids and were condemned to silence. More recently, the authors have been impressed by spectacular results with patients having lost their hearing during adulthood (postlingual). The challenge here is quite different, as its aim is to open up--and not to reopen--a child to a sensation that he has never perceived before. This allows the child to develop a coding, a recognition of the acoustic message. The first results are very encouraging. Scientifically, the implantation is also a research tool in various fields: surgical, neurophysiological, neuropsychological, speech therapy, social and cultural. The cochlear implant is an "avant-garde" project. It has changed our approach to profound deafness. It represents the only hope for the profoundly deaf person to reach a satisfactory rehabilitation and social integration.

Adaptation, Psychological↗

PubMed1991

[General principles of conception of cochlear implants].

Cochlear implants have greatly been developed on last ten years. Their diversity makes their use and choice more complex. The authors expose simply the physiopathology of the implanted auditory system and basic principles of cochlear implants. Cochlear implants are caracterised by the number of channels and electrodes (monochannel, multichannel), the strategy of encoding (analogiq, digital), the transmission of signal (per-cutaneous, electro-magnetic induction), the site of stimulation (extra or intra-cochlear), the signal wave (sinusoid, pulse), the diffusion of current (monopolar, bipolar).

Cochlear Implants↗

PubMed1990

Computed tomography: how accurate a predictor for cochlear implantation?

Cochlear implantation is an accepted medical treatment for profound bilateral postlinguistically acquired hearing loss. Because cochlear implants are still in the process of development, a detailed evaluation of the results of implantation is essential. However, the capability of predetermining the auditory benefit of a cochlear implant is limited and depends upon a number of factors. This report focuses upon the ability of computed tomography (CT) to predict surgical success and audiological results of multichannel cochlear implantation. It also addresses how the disease state might affect the functional benefit of the implant. After undergoing routine clinical and audiological evaluations, 28 cochlear implant candidates underwent CT scans in order to evaluate cochlear patency prior to surgery. Subsequently, 24 patients were implanted with either a single-or 22-channel device. Surgical findings were noted and postoperative audiological assessments of sound detection and speech discrimination were made. The CT risk factors that diminish the likelihood of a successful cochlear implant result are discussed based upon a retrospective comparison of preoperative CT results, surgical findings, and postsurgical audiological evaluations of the 14 patients who received a 22-channel implant. Analysis of the predictive capability of CT will allow clinicians to use that procedure more effectively in the presurgical assessment of cochlear implant candidates.

Adult↗

PubMed1988

Treatment of sensorineural hearing loss by cochlear implantation.

Cochlear implantation, a form of neural prosthesis, is now being employed for some profoundly deaf individuals. The pathophysiology of profound deafness, the strategies inherent in cochlear implantation, the differences between various cochlear implant strategies and designs, medical and otologic evaluation of implant candidates, and the surgical procedure are each discussed. The results in speech recognition and speech reading that have been obtained with four commonly used cochlear implant systems are also presented.

Cochlear Implants↗

PubMed1992

[3D imaging of the labyrinth: application to candidates for cochlear implant].

Cochlear implantation is a treatment for profound bilateral cochlear hearing loss. Two broad varieties of cochlear implants are used: single or multichannel device (22- channel) inserted either into the cochlea (tympanic ramp) or on the promontory on round window Imaging modalities have to predict cochlear patency prior surgery, an essential factor for choosing between intra or extra cochlear implant. Since March 1991, we have investigated 23 implant candidates to evaluate cochlear patency prior surgery, 6 patients underwent surgery: 4 had a multichannel and 2 had a monochannel electrode. Both CT and MRI play a role in pre operative study. CT easily predicts cochlear ossification and labyrinthine malformations MRI (3 D applications) with T 2 Weighted images, one millimeter thick, more clearly depicts labyrinthine liquid and can predict cochlear fibrosis before ossification.

Cochlear Implants↗

PubMed1991

What can we learn about hearing aids from cochlear implants?

Cochlear implants have changed the rehabilitation of profoundly hearing-impaired patients. A wide range of performance is reported for postlingually deaf adult patients using multichannel (Nucleus and Inerad) cochlear implants. For the 63 patients described here, performance ranges from 0 to 62% correct word recognition, from 0 to 98% lipreading enhancement measured as a percentage of the possible enhancement, and from 0 to 98% on understanding words in sentences. Prelingually deaf children also show benefit from their cochlear implants, but they require more time to obtain benefit than postlingually deaf children and adults. Experience with cochlear implants has suggested a few observations that could be useful to hearing aid development, including: (1) field trials are essential; (2) signal processing should preserve and enhance frequency resolution; (3) the fitting process for a sophisticated hearing aid may require several days to adjust properly; (4) fitting algorithms should focus on individuals rather than averages; (5) patients will wear a larger device if their handicap is great enough and if the improvement is sufficient; and (6) patients should and will accept expensive hearing aids.

Adult↗

PubMed1997

Surgical aspects of paediatric cochlear implantation.

Cochlear implantation in the paediatric population is now an accepted method of rehabilitating profoundly or totally deaf children. The problems of cochlear implantation in children with other significant medical problems are examined. A retrospective review of the records of the first 45 children implanted at our centre was carried out. The review focused on surgical factors and outcome in addition to variations in technique which have occurred since the programme began. Congenital hearing loss was the most common indication for implantation. Fifteen children (33 per cent) had other medical problems. Three cases of flap breakdown (two occurring after direct trauma to the package bed) and one case of a misplaced electrode requiring re-implantation accounted for the only major complications to date. Minor complications included hypertrophic scar formation and post-operative wound infection. All children were using their implants at the time of this review, but two have subsequently been explanted. Cochlear implantation of children with multiple medical problems requires acceptance of a slightly higher risk of complications.

Adolescent↗

PubMed1996

Update on cochlear implantation.

Cochlear implants are computerized devices that partially replace the transduction and encoding functions of the cochlea. Over the past 20 years studies have demonstrated that cochlear implants are safe and effective, with modern computer-based multichannel devices providing open-set word understanding for the majority of implanted postlingually deafened adults as well as pre- and postlingually deafened children. Advances in word processing strategy have led to ever-improving word recognition skills and recent studies have demonstrated that oral language develops in congenitally deaf children who use cochlear implants.

Adult↗

PubMed1997

Asynchronous interleaved stimulation (AIS): a new speech coding strategy for cochlear implant.

Cochlear implants use a fixed or F0 dependent stimulation rate, whatever the sound analysed (vowel or consonant) or procedure (fixed filters or FFT). We present a procedure which varies as a function of the input signal. This method is based on FFT analysis using a variable width analysis window. Short windows are applied on the transient part of the signal, providing poor frequency resolution but good time resolution; they permit us to accurately follow the speech signal in time during its fast temporal variations. Large windows are applied on the stationary parts of the signal, providing better frequency resolution but poor time resolution. Transient parts of the speech order this window switching; they are detected using the statistical properties of the FFT; moreover, the narrow windowing is coupled to an increase of the stimulation frequency. This strategy has been implemented using the DIGISONIC cochlear implant software, and clinically assessed in 6 regular cochlear implant users, on the basis of a consonant-vowel-consonant test. This Asynchronous-Interleaved-Stimulation (AIS) strategy provides the patients with better discrimination than fixed window FFT analysis. The coding protocol will be described and results presented.

Cochlear Implants↗

PubMed1997

[Asynchronous sequential stimulation. A new signal treatment for cochlear implants].

Cochlear implants use a fixed or FO dependent stimulation rate, whatever the sound analysed (vowel or consonant) and its analysis procedure (fixed filters or FFT). We present a procedure which varies as a function of the nature of the input signal. This method is based on FFT analysis using a variable with analysis window. Short windows are applied on the transient part of the signal, providing poor frequency resolution but good time resolution; they accurately permit to follow the speech signal in time during its fast temporal variations. Large windows are applied on the stationary parts of the signal, providing better frequency resolution, but poor time resolution. Transient parts of the speech order this window switching; they are detected using the statistical properties of the FFT; moreover the narrow windowing is coupled with an increase of the stimulation frequency. This strategy has been implemented using the Digisonic cochlear implant software, and clinically assessed on 6 regular cochlear implant users, owing to a consonant-vowel-consonant test. This Asynchronous-Interleaved-Stimulation (AIS) strategy provides the patients with better discrimination than fixed window FFT analysis. The coding protocol are described and results presented.

Acoustic Stimulation↗

PubMed1996

Complications of pediatric cochlear implantation.

Cochlear implantation has been established as a method of auditory rehabilitation for selected deaf children. However, as with any surgical procedure, complications can occur and may be particularly devastating in children. In this retrospective study, complications encountered in 100 consecutive cochlear implant surgeries in children were analyzed. Surgical problems were limited to one case of delayed, transient facial paresis and one cerebrospinal fluid gusher. These findings demonstrate that cochlear implantation can be performed safely with careful preoperative planning and meticulous surgical technique.

Cerebrospinal Fluid Otorrhea↗

PubMed1998

Digital imaging: a valuable technique for the postoperative assessment of cochlear implantation.

Cochlear implantation with a multi-channel electrode array which provides stimulation via the auditory nerve has become a standard treatment for profound deafness. Postoperative radiography demonstrates electrode position and enables confirmation of satisfactory intra-cochlear electrode placement. The number of active electrodes which have been inserted can be determined and possible complications such as electrode kinking or slippage can be assessed. We evaluated digital radiography with confirmation of electrode position by intermittent fluoroscopy and assessed the relative radiation dose of the digital technique, conventional radiography and CT scanning. Radiation dose for this method usually ranges between 40 microGy and 440 microGy compared with a single exposure on the skull stand which produces a dose to the region of the cochlea of 470 microGy and a CT exposure of 950 microGy. The digital technique is comfortable for the patient, easily reproducible and provides images of high diagnostic quality enabling each electrode to be identified, which is especially valuable in association with postoperative electrode mapping. It also involves a lower radiation dose than conventional radiography. We now use digital radiography for all postoperative cochlear implant assessment.

Adolescent↗

PubMed1998

[Predictive factors for speech perception in patients with cochlear implant].

Cochlear implant therapy is an epoch-making advance in artificial sensory organ transplants, but the positive effects on speech perception vary. Quantification theory type I, a multivariate analysis, was used to determine predictive factors for speech perception in patients with cochlear implants. Fifty-one postlingual deaf adults (18 male and 33 female, mean age, 53.4, mean duration of deafness, 8.6 years) were tested for speech perception three or more months after a Nucleus 22 channels cochlear implant. The cause of deafness in nine patients was labyrinthitis, ototoxicity in five, meningitis in three and unknown in the remaining 34. Speech perception was measured by vowel, consonant and word recognition using a live voice, and monosyllable, word and sentence recognition using a videodisc. All tests were administered in a sound only condition. Results of the univariate analysis indicated that age at implantation was correlated with monosyllable recognition, and duration of deafness was correlated with live voice word recognition. Residual hearing and coding strategy were both correlated with all outcome measures. The multivariate analysis revealed that coding strategy, duration of deafness, residual hearing and the number of electrodes were significant predictors of live voice word recognition in that order.

Adolescent↗

PubMed1998

Spiral CT image deblurring for cochlear implantation.

Cochlear implantation is the standard treatment for profound hearing loss. Preimplantation and postimplantation spiral computed tomography (CT) is essential in several key clinical and research aspects. The maximum image resolution with commercial spiral CT scanners is insufficient to define clearly anatomical features and implant electrode positions in the inner ear. In this paper, we develop an expectation-maximization (EM)-like iterative deblurring algorithm to achieve spiral CT image super-resolution for cochlear implantation, assuming a spatially invariant linear spiral CT system with a three-dimensional (3-D) separable Gaussian point spread function (PSF). We experimentally validate the 3-D Gaussian blurring model via phantom measurement and profile fitting. The imaging process is further expressed as convolution of an isotropic 3-D Gaussian PSF and a blurred underlying volumetric image. Under practical conditions, an oblique reconstructed section is approximated as convolution of an isotropic two-dimensional (2-D) Gaussian PSF and the corresponding actual cross section. The spiral CT image deblurring algorithm is formulated with sieve and resolution kernels for suppressing noise and edge artifacts. A typical cochlear cross section is used for evaluation, demonstrating a resolution gain up to 30%40% according to the correlation criterion. Physical phantoms, preimplantation and postimplantation patients are reconstructed into volumes of 0.1-mm cubic voxels. The patient images are digitally unwrapped along the central axis of the cochlea and the implanted electrode array respectively, then oblique sections orthogonal to the central axis formed. After deblurring, representation of structural features is substantially improved in all the cases.

Algorithms↗

PubMed1991

Cochlear implant.

Cochlear implantation to restore some of the hearing in the profound or totally cochlear deaf patient has been briefly presented. An approximate two year follow up has not shown any complications. The Nucleus 22 channel cochlear implant, as presently manufactured, is a very useful device to rehabilitate profoundly or totally cochlear deaf patients.

Cochlear Implants↗

PubMed1997

Basic neurophysiology of cochlear-implants.

Cochlear implants work because the fibers of the auditory nerve can be stimulated electrically. Currently used multi-channel electrodes distribute the stimuli to different cochlear places (place principle) and provide information on the fine-time structure of the acoustic stimulus thus allowing periodicity analysis by the central nervous system. The paper treats the limitations of current cochlear implant technologies and discusses conceivable improvements.

Auditory Pathways↗

PubMedDate not supplied

Introduction to cochlear implants.

Cochlear implants have been very successful in restoring partial hearing to profoundly deaf people. Many individuals with implants are now able to communicate and understand speech without lip-reading, and some are able to talk over the phone. Children with implants can develop spoken-language skills and attend normal schools (i.e., schools with normal-hearing children). The greatest benefits with cochlear implantation have occurred in patients who (1) acquired speech and language before their hearing loss, and (2) have shorter duration of deafness. Gradual, but steady, improvements in speech production and speech perception have also occurred in prelingually deafened adults or children.

Adult↗

PubMed1986

Contraindications to cochlear implantation.

Cochlear implantation is still a controversial surgical procedure because its results in providing hearing for the deaf patient are far from ideal. The possible benefits of implantation should be carefully weighed against the complications that might arise. Many individuals with profound deafness are candidates for this procedure; however, there are some patients who are not. Contraindications to cochlear implantation, absolute and relative, systemic and local, are discussed. The surgeon's decision to withhold surgery is based on these contraindications.

Age Factors↗