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Role of modern imaging technology in the implementation of pediatric cochlear implants.

Since 1989, 40 patients have received cochlear implants in our institution. Over the past 2 years, 17 children among these patients have undergone radiographic assessment combining magnetic resonance imaging (MRI) and high-resolution computed tomography (CT) scanning. Imaging is not essential, and is only used after assessment by a multidisciplinary team. However, the imaging results influence the choice of implant, and sometimes the side to be implanted. The first study is always CT, as it detects congenital abnormalities, and for children with a history of bacterial meningitis, it can detect signs of labyrinthine ossification that contraindicates or complicates cochlear implantation. These signs are not always visible with tomodensitometry, especially when fibrosis within the canal has not yet ossified. This examination also provides for postoperative confirmation of implant position in case of failure or complication. Over the past 3 years, MRI has been combined with tomodensitometry, especially with children having a history of meningitis. This examination provides a basis for evaluating the liquid nature of the labyrinth. A GE Signa 1.5-T unit was used by the authors, employing sequences of volumetric acquisition (steady state free precision with 1.5-mm image slices and an angle of 15 degrees to 35 degrees). Hence, modern imaging plays an important role when the decision to implant has already been made, particularly in the case of profoundly deaf children. We always use MRI in combination with a CT scanner in children with a history of meningitis.

Adolescent↗

Audiological management and performance of adult cochlear-implant patients.

We review the signal-processing strategies of three of the most common cochlear implants in use today, the single-channel House, the multichannel Nucleus, and the Ineraid devices. The results of 65 postlinguistically-deafened patients tested at The University of Iowa are reviewed. The tests include everyday sound, accent, word and sentence recognition, as well as noise/voice differentiation. For all tests, patients with the Nucleus and Ineraid cochlear implants outperformed those with the House implant. In general, selection criteria should focus on comparing the performance of Patients who have already received an implant. Prelinguistically-deafened adults are typically not good cochlear-impact candidates. Cochlear-implant teams should be aware of the enormous time commitment for testing and rehabilitation of these patients, and be prepared to handle frequent implant breakdowns. Nevertheless, cochlear-implant patients have been helped significantly be these devices.

Audiology↗

The value of nuclear scans in cochlear implant infections.

We discuss the diagnostic value of nuclear scintigraphy in the management of infections after cochlear implantation. A 56-year-old female (Case 1) and a 46-year-old female (Case 2) developed complaints of diffuse headache, 4 and 5 months after cochlear implantation, without other signs of infection during examination, laboratorial testing and initial computed tomography. In Case 1 we performed a technetium 99 m-difosfate scintigraphy, which showed an increased uptake in the right petrosal bone, suggestive of chronic osteomyelitis. This case failed conservative treatment and underwent complete explantation, after which 67gallium-citrate single-photon emission computed tomography normalized during follow-up. In Case 2 inflammation at the site of the cochlear implant was confirmed by performing a positron emission tomography scan, which showed an increased uptake. Case 2 was treated successfully with antibiotics. Both have no signs of recurrent infection. Nuclear scintigraphy can be the single valuable tool in case of a late low-grade infection after cochlear implantation. Delayed low-grade chronic osteomyelitis of the petrosal bone is a rare but dramatic complication after cochlear implantation. It can develop with minimal signs of infection.

Anti-Bacterial Agents↗

Meningitis following cochlear implantation: pathomechanisms, clinical symptoms, conservative and surgical treatments.

Pneumococcal otogenic meningitis is a rare postsurgical complication that can develop following stapedectomy or after cochlear implantation. The bacterial infection can be fatal in some instances. A recent increase in the incidence of otogenic meningitis among cochlear implant wearers is of concern. The majority of meningitis cases are associated with a 2-component electrode manufactured by one cochlear implant company. The device with the added 'positioner' component has been withdrawn from the market (FDA Public Health Web Notification: Cochlear Implant Recipients may be at Greater Risk for Meningitis, Updated: August 29, 2002, www.fda.gov/cdrh/safety/cochlear.html). Not all cases have been subsequent to otitis media and symptoms have developed from less than 24 h up to a few years after implantation. The purpose of this paper is to review and discuss the pathogenesis, pathology/bacteriology and to elaborate on some clinical features of otogenic meningitis in implanted children and adults. Essential aspects of surgery, electrode design, and cochleostomy seal are discussed. Conclusions are drawn from the available data and recommendations are made for good practice in cochlear implantation and follow-up.

Acute Disease↗

Indirect costs, cost-utility variations and the funding of paediatric cochlear implantation.

OBJECTIVE: To demonstrate the existence of variations in cost-utility associated with indirect costs in paediatric cochlear implantation; to illustrate the implications of this for purchasing decisions and; to posit a potential solution to anomalies in purchasing that may otherwise result when services are publicly funded. METHODS: Data was taken from published sources on the cost of implantation, outcomes measured in terms of quality adjusted life years (QALY) and in savings in education costs associated with paediatric cochlear implantation. Cost-utility ratios across education authorities were calculated using a single centre's implantation costs. RESULTS: Variations in savings across education authorities show that the cost per QALY gain associated with paediatric cochlear implantation can vary between approximately $12,000 and $18,000 assuming an exchange rate of $1.45 = 1 pound sterling for the same implant centre. These variations have the potential to produce situations in which less efficient implant centres are preferred by purchasers over more efficient ones or in which candidates with poorer outcomes are selected for funding over candidates with superior outcomes. It is important that savings associated with education be taken into consideration in evaluations intended to inform purchasing decisions regarding implantation. Equally it is important that potentially anomalous decisions be avoided if evaluations are to remain credible. It is argued that this may be achievable if public funding for implantation is determined at a national level and ring-fenced i.e. devoted exclusively to use in cochlear implantation.

Child↗

Longitudinal assessment of physiological and psychophysical measures in cochlear implant users.

OBJECTIVE: The purpose of this study was to evaluate the effects of long-term electrical stimulation on human cochlear implant users. DESIGN: Repeated measures of electrically evoked auditory brain steam response (EABR) threshold, slope of the EABR growth function, and behavioral measures of threshold and dynamic range were made for a group of 22 Ineraid cochlear implant users and 19 Nucleus cochlear implant users over a 3- to 5-yr period. RESULTS: Data from both Ineraid and Nucleus cochlear implant users suggest that EABR threshold, slope of the EABR growth function, and behavioral measures of threshold and dynamic range remain reasonably stable for periods up to 5 yr postimplant. CONCLUSIONS: The results of this study show little evidence that prolonged electrical stimulation through daily use of a cochlear implant has deleterious effects on the auditory system.

Cochlear Implants↗

Hearing preservation in cochlear implantation for electric acoustic stimulation.

OBJECTIVE: To evaluate the possibility of preservation of low-frequency hearing in atraumatic cochlear implant electrode insertion procedures for combined, ipsilateral electric and acoustic stimulation. MATERIAL AND METHODS: A total of 21 patients were implanted with a MED EL C40+ cochlear implant using an atraumatic electrode insertion technique to preserve residual low-frequency hearing. Pure-tone audiometric thresholds were measured pre- and postoperatively to evaluate the degree of preserved hearing. Speech discrimination tests in quiet and with background noise were performed in a patient with successful hearing preservation. RESULTS: Using the atraumatic electrode insertion procedure with an insertion depth of 360 degrees (18-24 mm), hearing preservation could be achieved in 18/21 patients (85.7%). Three patients (14.3%) lost their residual low-frequency hearing after the implantation. Residual hearing was preserved completely in 13 patients (61.9%) and partial hearing preservation was possible in 5 (23.8%). Preliminary speech discrimination tests showed a dramatic benefit for the combined electric and acoustic stimulation mode compared to cochlear implantation alone. CONCLUSION: Preservation of low-frequency hearing in cochlear implantation is possible in patients implanted because of profound high-frequency deafness. With the development of new, more atraumatic electrode designs, preservation of residual hearing should be further improved.

Acoustic Stimulation↗

Speech processing in vocoder-centric cochlear implants.

The principles of the most recent cochlear implant processors are similar to that of the channel vocoder, originally used for transmitting speech over telephone lines with much less bandwidth than that required for transmitting the unprocessed speech signal. An overview of the various vocoder-centric processing strategies proposed for cochlear implants since the late 1990s is provided including the strategies used in different commercially available implant processors. Special emphasis is placed on reviewing the strategies designed to enhance pitch information for potentially better music perception. The various noise suppression strategies proposed over the years based on multi-microphone and single-microphone inputs are also described.

Acoustic Stimulation↗

Recognition of "real-world" musical excerpts by cochlear implant recipients and normal-hearing adults.

OBJECTIVE: The purposes of this study were (a) to compare recognition of "real-world" music excerpts by postlingually deafened adults using cochlear implants and normal-hearing adults; (b) to compare the performance of cochlear implant recipients using different devices and processing strategies; and (c) to examine the variability among implant recipients in recognition of musical selections in relation to performance on speech perception tests, performance on cognitive tests, and demographic variables. DESIGN: Seventy-nine cochlear implant users and 30 normal-hearing adults were tested on open-set recognition of systematically selected excerpts from musical recordings heard in real life. The recognition accuracy of the two groups was compared for three musical genre: classical, country, and pop. Recognition accuracy was correlated with speech recognition scores, cognitive measures, and demographic measures, including musical background. RESULTS: Cochlear implant recipients were significantly less accurate in recognition of previously familiar (known before hearing loss) musical excerpts than normal-hearing adults (p < 0.001) for all three genre. Implant recipients were most accurate in the recognition of country items and least accurate in the recognition of classical items. There were no significant differences among implant recipients due to implant type (Nucleus, Clarion, or Ineraid), or programming strategy (SPEAK, CIS, or ACE). For cochlear implant recipients, correlations between melody recognition and other measures were moderate to weak in strength; those with statistically significant correlations included age at time of testing (negatively correlated), performance on selected speech perception tests, and the amount of focused music listening following implantation. CONCLUSIONS: Current-day cochlear implants are not effective in transmitting several key structural features (i.e., pitch, harmony, timbral blends) of music essential to open-set recognition of well-known musical selections. Consequently, implant recipients must rely on extracting those musical features most accessible through the implant, such as song lyrics or a characteristic rhythm pattern, to identify the sorts of musical selections heard in everyday life.

Acoustic Stimulation↗

Contact dermatitis to silicone after cochlear implantation.

Complications, although rare, do occur with cochlear implantation. We present a 2-year old with persistent erythema and pruritus over the implantation site with serous discharge from the implanted ear. Patch testing revealed contact dermatitis to silicone LSR-30 encasing the Nuclear Contour-24 device. Hypersensitivity was also noted to silicone LSR-30 in the Med-el device but not to silicone LSR-70 in the Advance Bionics device. Device explantation resulted in complete resolution of symptoms. The patient was then successfully reimplanted with the Advance Bionics device. Erythema and irritation at the implantation site, without leukocytosis, should prompt evaluation for silicone contact dermatitis.

Biocompatible Materials↗

Cochlear implantation of children with minimal open-set speech recognition skills.

OBJECTIVE: The purpose of this study was to evaluate the postoperative performance of 12 children who demonstrated some open-set speech recognition skills before receiving a Nucleus multichannel cochlear implant with a view toward expanding the selection criteria for cochlear implant candidacy to include children who derive minimal benefit from amplification. DESIGN: Pre- and postoperative performance of two groups of children were compared. Group 1 consisted of 12 children who demonstrated some open-set speech recognition skills before receiving a Nucleus multichannel cochlear implant (Borderline group). Group 2 consisted of 12 children who demonstrated no open-set speech recognition skills before implantation with a Nucleus device (Traditional group). In all children, candidacy was determined based on preimplant binaural aided performance. For most subjects, the poorer ear was selected for implantation. Mean pre- and postoperative speech recognition scores of the Borderline subjects were compared to determine the benefit provided by their cochlear implants. Secondly, matched-pair analyses were used to compare the mean speech recognition scores obtained by the Borderline and Traditional subjects. RESULTS: The scores of the Borderline group improved significantly on five of six speech recognition measures when 6 mo postoperative scores obtained with the implant were compared with preoperative test scores obtained with hearing aids. By the 12 mo postoperative interval, the scores of the Borderline group had improved significantly (p < 0.05) on all six measures. In contrast, scores obtained by the Traditional group had improved significantly on three of six measures at both the 6 and 12 mo postoperative intervals. Comparison of postoperative test scores revealed that the Borderline group scored significantly higher than the Traditional group on three of six measures at the 6 mo test interval and on six of six measures at the 12 mo test interval (p < 0.05). CONCLUSIONS: The findings of this study indicate that both groups derive significant benefit from their cochlear implants. Although the mean preoperative audiograms for the implanted ears did not differ significantly for the two groups of subjects, members of the Borderline group exhibited significantly better speech recognition skills than the Traditional group during the first year after implantation. These findings suggest that the increased auditory experience of the Borderline subjects positively influenced their performance with a cochlear implant. The authors advocate that the selection criteria used to determine pediatric cochlear implant candidacy be broadened to include consideration of children who demonstrate minimal open-set speech recognition skills.

Child↗

Perioperative electrical auditory brain stem response in candidates for pediatric cochlear implantation.

OBJECTIVE: The aim was to investigate the feasibility of recording the electrical auditory brain stem response (EABR) evoked by electrical stimulation at the promontory (Prom-EABR) as a tool to assist selection of the ear for cochlear implantation in young children. STUDY DESIGN: The study group consisted of young children for whom the decision to proceed with implantation with the Nucleus mini 22-channel cochlear implant (Cochlear (UK) Ltd., London, UK) had already been made. SETTING: The Prom-EABR was recorded after the children had been anesthetised, but before the start of surgery. PATIENTS: A group of 25 children (11 boys and 14 girls), whose age at implantation ranged from 2 years 11 months to 6 years 8 months (mean age, 4 years 5 months), were investigated. INTERVENTION: Recordings of the Prom-EABR were used to determine which ear would receive the cochlear implant, providing there were no preexisting contraindications regarding selection of the ear. MAIN OUTCOME MEASURE: It has been suggested from earlier studies that the characteristics of the amplitude input/output (I/O) function of the EABR are related to neuronal survival. If the ear with the "better" I/O function is chosen for implantation, it might be expected that these children will perform better on average than those in whom the ear has been selected at random. RESULTS: Reliable recordings of the Prom-EABR were achieved in 40 ears (80%) of the 50 ears in the study. In 20 of the 25 children the technique was actively employed for selection of the ear for implantation. CONCLUSIONS: Recording of the Prom-EABR in the operating theater is a viable technique. Future analysis of long-term outcome measures of performance with the implant will confirm or dispute the benefit of ear selection using the Prom-EABR.

Child↗

Recurrent extrusion of cochlear implant at an interval of 5 years.

OBJECTIVE: To describe two different types of device extrusion occurring in the same patient 1 and 6 years after cochlear implantation and to discuss the relation between the two extrusions and problems of cochlear implantation in patients with chronic suppurative otitis media. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENT AND INTERVENTIONS: The patient was a 52-year-old man with profound hearing loss in the right ear caused by chronic otitis media and deafness in the left ear caused by removal of an acoustic neuroma. Surgery for cleaning the tympanic cavity and reconstruction of the bony canal after previous radical mastoidectomy was performed in the right ear first. One year later, cochlear implantation was performed in this ear. RESULTS: One year after implantation, the anterior edge of the internal device of cochlear implant was exposed along the skin incision. This site was stable after corrective surgery. Five years after this operation, however, the posterior edge of the internal device extruded, accompanied by infection around the device. CONCLUSION: The two extrusions occurred with a long interval in between and at two different sites. The first extrusion occurred along the skin incision, and the second extrusion occurred away from the skin incision with infection around the device. The authors assumed that the first and the second extrusion occurred independently; the first extrusion was caused by insufficient blood supply resulting from scar formation from repeated mastoid operations and by pressure on the skin from the internal and external devices, and the second extrusion was caused by proliferated tissue pushing the device upward and against the skin as a result of chronic middle ear infection. The clinical course indicates that sufficiently long follow-up periods are needed to determine the usefulness of the prevention techniques for cochlear implantation in patients with chronic suppurative otitis media.

Cochlear Implantation↗

Analysis of programming maps and its application for balancing multichannel cochlear implants.

Channel balancing is important for correct perception when using multichannel cochlear implants. In this paper we analyse the effect of channel imbalance on hearing perception in cochlear-implanted patients. Based on warble tone audiometry measured for 10 implanted patients, we evaluate how hearing sensitivity is affected by an imbalance. We also study the distribution along the cochlea of the programming parameters for 146 patients. The parameters are compared for different groups of patients (defined taking into account the age at implantation, the stimulation mode, and the presence of severe cochlear damage). The aim of this study is to obtain information that can be useful for balancing the channels for the patients in the different groups, as well as to evaluate the effect of an imbalance on perception. These results provide some complementary information that can be applied to the correct fitting of the cochlear implant processor.

Acoustic Stimulation↗

Cochlear implantation after radical mastoidectomy: management of a challenging case.

Due to increasing experience and technological improvement, the selection criteria for cochlear implantation have improved. Cochlear implant application can now be performed in selected patients with pathological middle ear lesions. The surgical approach to a patient with a history of bilateral radical mastoidectomy is addressed in detail. The benefits of cochlear implantation in this case are also discussed.

Cholesteatoma, Middle Ear↗

Cause and repair of flap necrosis over cochlear implant.

OBJECTIVE: The aim of this report was to study the cause and treatment of flap-related complications over cochlear implant. SETTING: The study was performed in an academic tertiary referral center. PATIENT: A 53-year-old Japanese male patient had had two retro-auricular skin incisions for tympanomastoidectomy in the postauricular region before implantation of a cochlear implant. He also had worn a helmet daily during work in his factory. INTERVENTIONS: Corrective surgery was performed for reformation of the local blood supply to the overlying skin flap and reinforcement of the tissue overlying the implant by use of a superiorly based temporal muscle and fascia flap that were sutured with an inferiorly based muscle and fascia flap. RESULTS: We successfully transposed the flap covering the implant without explantation of the implant. CONCLUSIONS: The delayed development of flap necrosis was thought to be due to pressure necrosis produced by the band in the patient's helmet lying on the skin over the implant and to poor local blood supply in the postauricular area stemming from the two previous skin incisions for mastoid surgery performed for cholesteatoma. In those patients who wear helmets, it is important to position the cochlear implant sufficiently behind the ear and to avoid the use of a helmet.

Cochlear Implants↗

Cochlear implantation: preoperative counselling and postoperative problems.

Some patients cannot understand the reasons for a cochlear implant, nor the implications of such a device, and thus a clear explanation is required during patient counselling. Approximately one tenth of the patients with hearing loss examined in our hospital have received cochlear implants. Adequate preoperative examinations can make the surgery less difficult. Following cochlear implantation, speech comprehension of the patients with prelingual hearing loss is poor, and even patients with good speech comprehension have complaints about the clarity of the voice by the cochlear implant.

Adolescent↗

Objective intraoperative method to record averaged electromyographic stapedius muscle reflexes in cochlear implant patients.

We have developed a procedure to measure the averaged stapedius muscle reflex in response to electrical stimulation (AESR) with a cochlear implant. The AESR, as activated by ipsilateral stimulation with a cochlear implant, was investigated intra-operatively in a series of 12 children. After the cochlear implant was placed into the cochlea and secured by the surgeon, an electromyographic (EMG) needle electrode was gently placed into the stapedius muscle. During stimulation of the cochlear implant, the stapedius reflex was monitored visually (VESR) and as an averaged EMG response (AESR). Consistent AESRs were obtained in 7 of the 12 children. These measures provide a method to obtain stapedius muscle responses that may be helpful in the programming of young children with cochlear implants. Comparative post-operative measures were also obtained, including behavioral threshold levels, behavioral comfort levels, and the contralateral stapedius reflex threshold (ESR) on selected electrodes.

Auditory Threshold↗