Evaluation of the high-resolution speech coding strategy for the Clarion CII cochlear implant system

Four postlinguistically deafened adults were implanted with the Clarion CII cochlear implant with the HiFocus II electrode in an evaluation of performance with a new speech coding strategy (high resolution) compared with current speech coding strategies (multiple pulsatile sampler, continuous interleaved sampling, and simultaneous analog stimulation). These strategies were implemented in the Platinum speech processor from Advanced Bionics Corporation (Sylmar, CA). Postoperatively, subjects were fitted with the traditional coding strategies and over the first month were allowed to determine their strategy of choice. This strategy was used to evaluate open-set speech recognition performance at 1 month and 3 months postfitting. At 3 months postfitting, subjects were reprogrammed with the high-resolution strategy. They returned for speech recognition testing at 1 month and 3 months postfitting with this strategy. Performance was significantly better with the high-resolution strategy for all four subjects, particularly when listening to speech in background noise. This finding was in agreement with their strong preference for the high-resolution strategy, and all four patients continue to use the high-resolution strategy.

Cochlear implantation update

Cochlear implantation is recognized as a valuable intervention with important implications for the acquisition of speech perception and verbal language in children with severe to profound hearing impairment. Auditory rehabilitation, language intervention, and close coordination between parents, schools, and the implant center are necessary to maximize efficacy. Early identification of hearing loss, early hearing aid use and language intervention, and cochlear implantation by 2 years of age are positive predictors for language acquisition that can approach the levels of normal-hearing children. There are early indications that increased access to mainstream education and gains in quality of life are long-term benefits that render cochlear implantation a cost-effective intervention.

An investigation of input level range for the nucleus 24 cochlear implant system: speech perception performance, program preference, and loudness comfort ratings

OBJECTIVE

Cochlear implant recipients often have limited access to lower level speech sounds. In this study we evaluated the effects of varying the input range characteristics of the Nucleus 24 cochlear implant system on recognition of vowels, consonants, and sentences in noise and on listening in everyday life.

DESIGN

Twelve subjects participated in the study that was divided into two parts. In Part 1 subjects used speech processor (Nucleus 24 SPrint trade mark ) programs adjusted for three input sensitivity settings: a standard or default microphone sensitivity setting (MS 8), a setting that increased the input sensitivity by 10.5 dB (MS 15), and the same setting that increased input sensitivity but also incorporated the automatic sensitivity control (ASC; i.e., MS 15A) that is designed to reduce the loudness of noise. The default instantaneous input dynamic range (IIDR) of 30 dB was used in these programs (i.e., base level of 4; BL 4). Subjects were tested using each sensitivity program with vowels and consonants presented at very low to casual conversational levels of 40 dB SPL and 55 dB SPL, respectively. They were also tested with sentences presented at a raised level of 65 dB SPL in multi-talker babble at individually determined signal to noise ratios. In addition, subjects were given experience outside of the laboratory for several weeks. They were asked to complete a questionnaire where they compared the programs in different listening situations as well as the loudness of environmental sounds, and state the setting they preferred overall. In Part 2 of the study, subjects used two programs. The first program was their preferred sensitivity program from Part 1 that had an IIDR of 30 dB (BL 4). Seven subjects used MS 8 and four used MS 15, and one used the noise reduction program MS 15A. The second program used the same microphone sensitivity but had the IIDR extended by an additional 8 to 10 dB (BL 1/0). These two programs were evaluated similarly in the speech laboratory and with take-home experience as in Part 1. RESULTS PART 1: Increasing the microphone input sensitivity by 10.5 dB (from MS 8 to MS 15) significantly improved the perception of vowels and consonants at 40 and 55 dB SPL. The group mean improvement in vowel scores was 25 percentage points at 40 dB SPL and 4 percentage points at 55 dB SPL. The group mean improvement for consonants was 23 percentage points at 40 dB SPL and 11 percentage points at 55 dB SPL. Increased input sensitivity did not significantly reduce the perception of sentences presented at 65 dB SPL in babble despite the fact that speech peaks were then within the compressed range above the SPrint processor's automatic gain control (AGC) knee-point. Although there was a demonstrable advantage for perception of low-level speech with the higher input sensitivity (MS 15 and 15A), seven of the 12 subjects preferred MS 8, four preferred MS 15 or 15A, and one had no preference overall. Approximately half the subjects preferred MS 8 across the 18 listening situations, whereas an average of two subjects preferred MS 15 or 15A. The increased microphone sensitivity of MS 15 substantially increased the loudness of environmental sounds. However, use of the ASC noise reduction setting with MS 15 reduced the loudness of environmental sounds to equal or below that for MS 8. RESULTS PART 2: The increased instantaneous input range gave some improvement (8 to 9 percentage points for the 40 dB SPL presentation level) in the perception of consonants. There was no statistically significant increase in vowel scores. Mean scores for sentences presented at 65 dB SPL in babble were significantly lower (5 percentage points) for the increased IIDR setting. Subjects had no preference for the increased IIDR over the default. The IIDR setting had no effect on the loudness of environmental sounds.

CONCLUSIONS

Given the fact that individuals differ in threshold (T) and comfort (C) levels for electrical stimulation, and preferred microphone sensitivity, volume control, and noise-reduction settings, it is essential for the clinicid recipient to determine what combination is best for the individual over several sessions. The results of this study clearly show the advantage of using higher microphone sensitivity settings than the default MS 8 to provide better speech recognition for low-level stimuli. However, it was also necessary to adjust other parameters such as map C levels, automatic sensitivity control and base level, to optimize loudness comfort in the diversity of listening situations an individual encounters in everyday life.

Technical report: modification of a cochlear implant electrode for drug delivery to the inner ear

OBJECTIVE

To investigate the possibility of modifying a cochlear implant electrode for the purpose of drug delivery to the cochlea.

BACKGROUND

Animal experiments suggest that local therapy of the inner ear could be a promising new approach to the interventional treatment of inner ear disease, and that pharmacologic intervention could possibly enhance cochlear implant performance. One of the key aspects is the deployment of a means of drug delivery to the human inner ear.

METHODS

The tip of the Contour electrode array was cut to open the lumen of the array, and a connecting piece was developed to connect the electrode to a pump. The feasibility of using the array for drug delivery was tested using both an Alzet mini-osmotic pump and a mechanical pump. The connection was tested for its stability in terms of leakage and resistance to tractive forces. The system was also applied to temporal bones to evaluate its applicability to the human cochlea.

RESULTS

The modified Contour electrode is easy to handle in temporal bones and can be used to simulate drug delivery to the inner ear. The connection to the pump was sealed for all tested pump rates and resisted tractive forces up to 50 N.

CONCLUSIONS

The described modified electrode could provide a safe and easy-to-handle means of combining electrical stimulation with the beneficial effects of a local drug therapy applied to the inner ear.

Coding of sounds in the auditory system and its relevance to signal processing and coding in cochlear implants

OBJECTIVE

To review how the properties of sounds are "coded" in the normal auditory system and to discuss the extent to which cochlear implants can and do represent these codes.

DATA SOURCES

Data are taken from published studies of the response of the cochlea and auditory nerve to simple and complex stimuli, in both the normal and the electrically stimulated ear. REVIEW CONTENT: The review describes: 1) the coding in the normal auditory system of overall level (which partly determines perceived loudness), spectral shape (which partly determines perceived timbre and the identity of speech sounds), periodicity (which partly determines pitch), and sound location; 2) the role of the active mechanism in the cochlea, and particularly the fast-acting compression associated with that mechanism; 3) the neural response patterns evoked by cochlear implants; and 4) how the response patterns evoked by implants differ from those observed in the normal auditory system in response to sound. A series of specific issues is then discussed, including: 1) how to compensate for the loss of cochlear compression; 2) the effective number of independent channels in a normal ear and in cochlear implantees; 3) the importance of independence of responses across neurons; 4) the stochastic nature of normal neural responses; 5) the possible role of across-channel coincidence detection; and 6) potential benefits of binaural implantation.

CONCLUSIONS

Current cochlear implants do not adequately reproduce several aspects of the neural coding of sound in the normal auditory system. Improved electrode arrays and coding systems may lead to improved coding and, it is hoped, to better performance.

Speech coding strategies and revised cochlear implant candidacy: an analysis of post-implant performance

OBJECTIVE

Technological advances in cochlear implant systems on which a sequence of speech coding strategies have been implemented seem to have resulted in improved speech perception. However, changing selection criteria for implantation have coincided with evolving technology and may confound post-implantation speech perception performance. This study compares speech coding strategy with speech perception performance in severe and profound postlingually deafened adults using one of three successive generations of Nucleus Cochlear Implant speech processors (i.e., Mini Speech Processor, Spectra 22, and SPrint) implementing three speech coding strategies (i.e., MPEAK, SPEAK, and Advanced Combination Encoders; Cochlear Corporation, Englewood, CO, U.S.A.).

STUDY DESIGN

Four cohorts of patients were retrospectively reviewed.

SETTING

Multicenter, tertiary referral cochlear implant programs in Ontario, Canada.

METHODS

Four cohorts of patients (n = 139) were identified based on preimplant audiological measures, duration of deafness, device type, and speech coding strategy. Word and sentence recognition scores at 12 months after implantation were compared using MPEAK with SPEAK22 implemented on the Nucleus 22 speech processors (Mini Speech Processor and Spectra22, respectively) and SPEAK24 as well as Advanced Combination Encoders implemented on the Nucleus 24 SPrint processor.

RESULTS

Open-set speech recognition batteries revealed significant improvements in word and sentence scores as advancing technology implemented new speech coding strategies. Subgroup analysis of profoundly deafened patients supported this. Analysis of covariance confirmed that the measured differences could not be accounted for by changing selection criteria for implantation.

CONCLUSION

Improvements in performance can be attributed to evolving speech coding strategies and speech processors rather than to differences in preimplant candidacy.

Usher syndrome and cochlear implantation

OBJECTIVE

To evaluate the symptoms leading to diagnosis and the quality of rehabilitation after cochlear implantation in Usher syndrome.

STUDY DESIGN

Retrospective cohort study.

SETTING

ENT department of a tertiary referral hospital.

PATIENTS

Among 210 patients given an implantation in the Ear, Nose, and Throat department, 185 were congenitally deaf and 13 had Usher syndrome (7.0%). Five had a family history of Usher, and eight were sporadic cases. Eleven cases were Usher type I, one was Usher type III, and one was not classified. The age at implantation ranged from 18 months to 44 years (mean, 6 years 1 month). The mean follow-up was 52 months (range, 9 months to 9 years).

MAIN OUTCOME MEASURES

All patients had audiophonological and clinical examination, computed tomography scan of the temporal bones, ophthalmologic examination with fundoscopy, and an electroretinogram. Cerebral magnetic resonance imaging and vestibular examination were performed in 9 of 13 and 10 of 13 cases, respectively. Logopedic outcome measured preimplant and postimplant closed- and open-set word recognition and oral expression at follow-up.

RESULTS

The most frequent initial sign of Usher syndrome was delayed walking, with a mean age of 20 months. Among the 172 other congenitally deaf children with implants, when deafness was not associated with other neurologic disorders, the mean age at walking was 14 months (p < 0.001). The fundoscopy was always abnormal after the age of 5 years, and the electroretinogram was abnormal in all cases. Vestibular function was abnormal in all but one case (nonclassified). The computed tomography scan and the magnetic resonance imaging were always normal. Logopedic results with cochlear implants showed good perception skills in all but one case. The best perceptive results were obtained in children implanted before the age of 9 years. Oral language had significantly progressed in 9 of 13 at follow-up. There was no relation between the visual acuity and the logopedic results.

CONCLUSION

The earliest clinical sign associated with deafness evoking Usher syndrome is late walking. The electroretinogram is the only reliable examination to enable the diagnosis. When severe profound deafness is associated with late walking, the electroretinogram should be systematically proposed. Logopedic results are linked to precocity of implantation, and early Usher's diagnosis contributes to optimize speech therapy.

Vestibular dysfunction after cochlear implantation

OBJECTIVE

To determine the prevalence, symptom characteristics, and potential risk factors for vestibular symptoms after cochlear implantation.

STUDY DESIGN

Case-control study design embedded within an ongoing cohort of patients undergoing implantation.

SETTING

Academic medical center cochlear implant research program funded by the National Institutes of Health.

PATIENTS

Seventy five eligible consecutive patients undergoing cochlear implantation.

INTERVENTION

Medical record review.

MAIN OUTCOME MEASURE

Recorded symptoms of vestibular symptoms after cochlear implantation. Subjects with vestibular symptoms were considered case subjects; those without vestibular symptoms were considered control subjects.

RESULTS

Twenty-nine of 75 (39%) patients experienced dizziness postoperatively. Four patients experienced a single, transient acute vertigo attack occurring less than 24 hours after surgery. The majority, 25 patients, experienced delayed, episodic onset of vertigo. The median (interquartile range) time of delayed onset was 74 (26-377) days after implantation. Delayed dizziness manifested as spontaneous episodic or positional vertigo. Preoperative dizziness, age at implantation, and age at onset of hearing loss were significantly greater in the dizzy group. Preoperative electronystagmography did not differentiate between groups.

CONCLUSIONS

Thirty-nine percent (29/75) of subjects with implants were dizzy after implantation. The majority of subjects experienced dizziness in a delayed episodic fashion. Dizziness was not related to implant activation. It seemed that delayed dizziness was not related to immediate surgical intervention but could result from chronic changes occurring in the inner ear; there was some suggestion this could take the form of endolymphatic hydrops.

[Initial information on adjustment of speech processor of the cochlear implant]

Adjustment of a speech processor of the cochlear implant is the first procedure in rehabilitation of patients after cochlear implantation. Influence of setting understated and overstated threshold levels of current perception on processing of a speech signal was studied. The results of the study show that only precise estimation of current perception threshold and comfortable loudness allow transmitting maximal acoustic information for each patient.

Perceptual learning following changes in the frequency-to-electrode assignment with the Nucleus-22 cochlear implant

The goal of the present study was to investigate the time course of adaptation by experienced cochlear implant users to a shifted frequency-to-electrode assignment in their speech processors. Speech recognition performance of three Nucleus-22 cochlear implant users was measured over a 3-month period, during which the implant listeners continuously wore "experimental" speech processors that were purposely shifted by 2-4 mm in terms of the frequency-to-electrode assignment relative to their normal processor. Baseline speech performance was measured with each subject's clinically assigned speech processor just prior to implementation of the experimental processor. Baseline speech performance was measured again after the 3-month test period, immediately following the reinstallation of the clinically assigned processor settings. Speech performance with the experimental processor was measured four times during the first week, and weekly thereafter over the 3-month period. Results showed that the experimental processor produced significantly lower performance on all measures of speech recognition immediately following implementation. Over the 3-month test period, consonant and HINT sentence recognition with the experimental processors gradually approached a performance level comparable to but still significantly below the baseline and postexperiment measures made with the clinically assigned processor. However, vowel and TIMIT sentence recognition with the experimental processors remained far below the level of the baseline measures even at the end of the 3-month experimental period. There was no significant change in performance with the clinically assigned processor before or after fitting with the experimental processor. The results suggest that a long-time exposure to a new pattern of stimulation may not be able to compensate for the deficit in performance caused by a 2-4-mm shift in the tonotopic location of stimulation, at least within a 3-month period.

Effects of stimulation rate with the Nucleus 24 ACE speech coding strategy

OBJECTIVE

The primary objective of the study was to determine whether individual cochlear implant recipients recognize speech better with an electrical stimulation rate of 720 or 1800 pulses per second per channel (pps/ch) using the Nucleus 24 Advanced Combination Encoder (ACE) speech coding strategy. The secondary objective was to determine, for each active electrode, the relation between psychophysical measures and MAP minimum and maximum stimulation levels for each rate, as well as the stability of MAP minimum and maximum levels during the study.

DESIGN

Eight postlinguistically deaf adults implanted with the Nucleus 24 device participated in this study comparing the effect of a moderate (720 pps/ch) and a fast (1800 pps/ch) rate of electrical stimulation on speech recognition of words in quiet and sentences in noise presented at 50, 60, and 70 dB SPL in the laboratory and on listening to sound in everyday life over a 14-wk time period. At the beginning of the study, psychophysical measures (i.e., counted threshold and maximum acceptable loudness [MAL] levels) were obtained for each active electrode with each of the two rates to initially set MAP minimum and maximum stimulation levels. These levels were then adjusted to make speech and environmental sound clear and comfortable in everyday life. Threshold and MAL levels were obtained again half way through the study to monitor possible hearing changes. A four-phase test design for evaluation of speech recognition was followed; an equal number of subjects started with each of the two rates and alternated rates for each phase. In the last 2 wk of each phase, word and sentence scores were obtained, and subjects responded to a questionnaire. For the group, factorial analyses of variance were conducted for subject, stimulation rate, and time period (first two phases versus second two phases) for words, phonemes within words, and sentences at each level. Additional analyses were obtained for individual subjects.

RESULTS

Group mean scores across time periods were significantly higher for 1800 pps/ch than 720 pps/ch for phonemes and sentences in noise at 50 dB SPL. There was no significant difference in scores for phonemes and sentences at 60 and 70 dB SPL or for words at any of the three levels. Group mean scores across stimulation rate were significantly higher during the second half than the first half of the study for words, phonemes, and sentences at 50 dB SPL. This result is consistent with subjects learning to recognize speech cues near threshold. A subject by rate interaction was seen for sentences at 70 dB SPL and for all three speech measures at 50 dB SPL. These interactions reflect the fact that two subjects performed significantly better with 720 pps/ch, whereas two other subjects performed significantly better with 1800 pps/ch. Responses to the questionnaire indicated that two subjects preferred 720 pps/ch, three preferred 1800 pps/ch, and three had no preference. The minimum and/or maximum levels in most subjects' final MAPs differed from the psychophysical measures for both rates. Changes in Current Level at threshold and MAL were minimal from the first to the second half of the study for each rate.

CONCLUSIONS

More than half the subjects preferred one of the two rates for use in everyday life, and four subjects performed significantly better with one of the two rates on at least one test measure. These findings underscore the clinical importance of creating MAPs for each implant recipient that include at least a moderate and a fast rate within ACE during the first months of device use. Given the significant learning effects for soft speech that occurred over several weeks use of each rate in this study, it is suggested that each rate be used alone for a week or two before comparing them and deciding which provides more benefit. In addition, adjustments in an individual's MAP minimum and maximum levels are needed at each rate so soft and normal conversational speech as well as loud sound are clear and comfortable in everyday life.

Cochlear implantation without mastoidectomy: the pericanal electrode insertion technique

OBJECTIVE

A new minimally invasive cochlear implantation method with direct electrode insertion through the external auditory canal (EAC) is presented.

MATERIAL AND METHODS

Surgery begins with a retroauricular skin incision. The bony surface of the mastoid plane behind the ear is dissected free and the skin of the EAC is elevated together with the posterior part of the tympanic membrane. Cochleostomy is performed through the EAC with a microdrill anterior to the round window. A rim is drilled into the postero-superior region of the bony EAC immediately above the incus towards the outer border of the EAC and connected to the retroauricular surface by a short tunnel. The implant device is placed in the usual retroauricular area. The electrode is inserted through the tunnel and rim into the tympanic cavity and pushed into the cochleostomy hole. The electrode is immobilized in the rim using glass ionomer cement and covered with bone dust. After placement of the ground electrode, the retroauricular incision is closed. The tympano-meatal flap is replaced and a dressing is put into the EAC.

RESULTS

The new method has been applied thus far in 15 adults and pre-adolescent deaf patients (8 females, 7 males). A MED-EL Combi 40 + device was used in 14 patients and a Nucleus CI24M in 1. Pericanal electrode insertion was easy, with insertion depths into the cochlea of > or = 30 mm with the MED-EL and of 20 mm with the Nucleus device. There were no surgical complications, infections or electrode extrusions during postoperative observation periods ranging from 6 months to > 2 years. The functional results were comparable to those obtained with cochlear implantation via mastoidectomy. The pericanal electrode insertion technique has several advantages, the most important being that the danger of facial nerve damage is minimized and that the operating time is reduced by up to 50%.

CONCLUSION

Cochlear implantation with pericanal electrode insertion is a simple, fast and particularly safe option which may replace the classical transmastoidal cochlear implantation method in adults and older children.

The nucleus contour electrode array: an electrophysiological study

OBJECTIVE/HYPOTHESIS

Positioning intracochlear electrodes adjacent to the modiolus would lead to a reduction in threshold levels and latencies, as measured with electrically evoked auditory brainstems responses. Recently, Cochlear Corporation introduced a new perimodiolar array (Contour electrode) characterized by a platinum stylet inserted into the array's silicone carrier that keeps the electrode in a straightened configuration before insertion. After completion of the insertion, the withdrawal of the stylet allows the array to coil within the cochlea positioning electrodes closer to the modiolus. The purpose of the study was to analyze the stimulation properties of the Contour electrode by evaluating the effects of the withdrawal of the stylet on electrical auditory brainstem response (EABR) characteristics.

METHODS

Electrical auditory brainstem response registrations were performed intraoperatively on three electrodes (1 apical, 1 medial, 1 basal) before and after the removal of the stylet in 10 patients implanted with the Nucleus 24 Contour device. A within-patient comparison of EABR characteristics was performed. The Student test was used to assess differences in EABR measures obtained before and after the stylet removal.

RESULTS

Mean EABR thresholds were significantly lower after the removal of the stylet than with the stylet in situ for all three electrodes tested. After the removal of the stylet, latencies of waves III and V significantly decreased, whereas amplitudes significantly increased.

CONCLUSION

Reduction in EABR threshold levels and latencies as well as an increase in waves III and V amplitudes after the stylet removal all demonstrate the effectiveness of the Contour system in positioning intracochlear electrodes closer to auditory neurons.

Modiolar proximity of three perimodiolar cochlear implant electrodes

A new generation of cochlear implant electrodes has been designed to position the stimulating contacts close to the modiolus in order to reduce power consumption and increase stimulation selectivity. The purpose of this study was to assess electrode position in the cochlea for three recently designed electrodes. Fifteen cadaveric temporal bones were implanted with one of three perimodiolar electrode arrays: Nucleus Contour; Med-El Combi40+ PM (developmental version); and Clarion HiFocus II. Image-enhanced videofluoroscopy and computer morphometrics were used to assess stimulating contact position relative to the modiolus. The mean distance (+/- 1 standard deviation) to the modiolus for all electrode contacts was 0.33 (+/-0.24), 0.30 (+/-0.27) and 0.16 mm (+/-0.19) for the Contour, Combi40+ PM and HiFocus II arrays, respectively. In addition, dynamic videofluoroscopy was used to correlate device-specific insertion characteristics with contact-to-modiolus distance. All three devices were successful in terms of locating electrode contacts very close to the modiolar wall.

Cochlear and brainstem implantation

Cochlear implantation is an established habilitative and rehabilitative option for profoundly deafened individuals over 1 year of age who derive limited benefit from conventional hearing aids. Auditory performance varies among individuals and is determined primarily by age at implantation, pre-existence of speech and language skills, and the time interval between onset of deafness and implantation. Successful implant users generally demonstrate improved auditory abilities and speech production skills beyond those achieved with hearing aids. Multichannel ABIs can provide useful auditory information to patients with NF-2 who have lost integrity of auditory nerves following removal of vestibular schwannomas. The implant allows for awareness of environmental sounds and, potentially, speech recognition. Most patients undergoing implantation demonstrate improved lip-reading skills, and exceptional performers achieve understanding of open-set speech.

[Force-based local navigation in robot-assisted implantation bed anlage in the lateral skull base. An experimental study]

Excellent precision, miss of retiring, reproducibility are main characteristics of robots in the operating theatre. Because of these facts their use for surgery in the lateral scull base is of great interest. In recent experiments we determined process parameters for robot assisted reaming of a cochlea implant bed and for a mastoidectomy. These results suggested that optimizing parameters for thrilling with the robot is needed. Therefore we implemented a suitable reaming curve from the geometrical data of the implant and a force controlled process control for robot assisted reaming at the lateral scull base. Experiments were performed with an industrial robot on animal and human scull base specimen. Because of online force detection and feedback of sensory data the reaming with the robot was controlled. With increasing force values above a defined limit feed rates were automatically regulated. Furthermore we were able to detect contact of the thrill to dura mater by analyzing the force values. With the new computer program the desired implant bed was exactly prepared. Our examinations showed a successful reaming of an implant bed in the lateral scull base with a robot. Because of a force controlled reaming process locale navigation is possible and enables careful thrilling with a robot.

The role of radiographic phase-contrast imaging in the development of intracochlear electrode arrays

OBJECTIVE

This study describes the application of a new radiographic imaging modality, phase-contrast radiography, to in vitro human temporal bone imaging and investigates its use in the development of new electrode arrays for cochlear implants.

BACKGROUND

The development of perimodiolar electrode arrays for cochlear implants requires detailed information from postoperative radiologic assessment on the position of the array in relation to the cochlear structures. Current standard radiographic techniques provide only limited details.

MATERIALS AND METHODS

Nucleus standard electrode arrays and perimodiolar Contour electrode arrays were implanted into the scala tympani of 11 human temporal bones. Both conventional and phase-contrast radiographs were taken of each temporal bone for comparative purposes.

RESULTS

Phase-contrast imaging provides better visualization of anatomic details of the inner ear and of the structure of the intracochlear electrode array, and better definition of electrode location in relation to cochlear walls.

CONCLUSION

Phase-contrast radiography offers significant improvement over conventional radiography in images of in vitro human temporal bones. It seems to be a valuable tool in the development of intracochlear electrode arrays and cochlear implant research. However, this new radiographic technique still requires certain computational and physics challenges to be addressed before its clinical use can be established.

Cochlear reimplantation: surgical techniques and functional results

OBJECTIVES/HYPOTHESIS

The most common indication for cochlear reimplantation is device failure. Other, less frequent indications consist of "upgrades" (e.g., single to multichannel), infection, and flap breakdown. Although the percentage of failures has decreased over time, an occasional patient requires reimplantation because of device malfunction. The varying designs of internal receiver/stimulators and electrode arrays mandate an examination of the nature and effects of reimplantation for the individual designs. The purpose of the current study was to investigate the reimplantation of several implant designs and to determine whether differences in surgical technique, anatomical findings, and postoperative performance exist.

STUDY DESIGN

Retrospective chart review.

METHODS

The subjects were 33 of 618 severely to profoundly deaf adults and children who had implantation at the New York University Medical Center (New York, NY) between February 1984 and December 2000. The subjects had previously had implantation with either a single-channel 3M/House (House Ear Institute, Los Angeles, CA) or 3M/Vienna (Technical University of Vienna, Vienna, Austria) device or with one of the multichannel Clarion (Advanced Bionics, Sylmar, CA), Ineraid (Smith & Nephew Richards, TN), or Nucleus (including the Contour) devices (Cochlear Corp., Englewood, CO) before reimplantation.

RESULTS

Length of use before reimplantation ranged from 1 month to 13 years and included traumatic and atraumatic (electronic) failures, as well as device extrusion or infection. Results indicated that postoperative performance was either equal to or better than scores before failure. None of the devices explanted caused damage that precluded the implantation of the same or an upgraded device. These findings support the efficacy and safety of internal implant designs as related to the maintenance of a functional cochlea for the purpose of reimplantation.

CONCLUSIONS

Cochlear reimplantation can be performed safely and without decrement to performance. The number of implanted electrodes at reinsertion were either the same or greater in all cases.

Cochlear implantation in healthy and otitis-prone children: a prospective study

OBJECTIVE

To evaluate and compare the timing of surgery, intraoperative findings, and otitis media-related outcome of cochlear implantation in children who are otitis-prone with their counterparts who are not otitis-prone.

STUDY DESIGN

Prospective.

METHODS

Children referred for cochlear implantation were assigned to a non-otitis-prone group (group A: normal otoscopy on their first visit after referral) or an otitis-prone group (group B: current or a recent history of otitis media at referral). Group B patients were managed using a structured protocol aimed at preimplantation otitis media control. The study reviewed pre-, intra-, and postoperative data.

RESULTS

Of the 18 children studied, 8 were assigned to group A (mean age at referral, 40.6 mo) and 10 to group B (mean age at referral, 31.6 mo). For otitis media control, all otitis-prone children underwent ventilating tube insertion (various numbers of procedures before implantation). Only one otitis-prone child required cortical mastoidectomy also. Time from referral to implantation was similar in the two groups (mean, 6.6 mo). High-resolution computed tomography data showed mastoid pneumatization to be significantly smaller in the otitis-prone group, but the facial recess was not smaller in this group. During implantation, 10 children had inflamed middle ear mucosa. Seven of these belonged to group B. All of these seven children had a round window niche obliterated by the inflamed mucosa, which had to be removed for round window membrane identification. After implantation, only one child had drainage through the ventilating tube for more than 1 week. Two children in group B developed otitis media (1 year postimplantation) that was overcome within 1 week. There were no otitis media-related complications.

CONCLUSIONS

If a structured protocol is used for the control of otitis media before cochlear implantation, otitis media should not require a delay in implantation. In otitis media-prone children, the round window niche is often obscured by inflamed mucosa. Its removal is mandatory for identification of the round window membrane. After cochlear implantation, otitis media is not a frequent occurrence.

[Applications for a robot in the lateral skull base. Evaluation of robot-assisted mastoidectomy in an anatomic specimen]

In the past decade, a great variety of robot systems have been applied in numerous areas of life. In the public health system, robots are increasingly used in the operating theater. The potential for reproducibility and predictability was one of the main arguments for the use of robots in orthopedic treatment of bones, especially the implantation of a cementless total hip replacement. In otorhinolaryngological surgery (ENT), different hearing aids were developed: the cochlea implant for the deaf or the totally implantable hearing aid for the hearing impaired. Their site of implantation is localized in the lateral skull base. Removal of the bone mass with the reamer requires both great precision and considerable physical effort on the part of the surgeon, which does not result in an ergonomic operating technique. The following project describes the evaluation of processing parameters for a robot-assisted mastoidectomy to expose an implantation bed. The goal was to establish different parameters for robot-controlled reaming in the calotte or mastoid. In addition, several parameters were tested for their influence on surface structure, procedure reliability, and quality as well as the ability of the Mayfield clip to stabilize the head during the operation.

An integrated simulator for surgery of the petrous bone

This paper describes work being undertaken as part of the IERAPSI (Integrated Environment for the Rehearsal and Panning of Surgical Intervention) project. The project is focussing on surgery for the petrous bone, and brings together a consortium of European clinicians and technology providers working in this field. The paper presents the results of a comprehensive user task analysis that has been carried out in the first phase of the IERAPSI project, and details the current status of development of a pre operative planning environment and a physically-based surgical simulator.