Cochlear Implantation and Other Treatments in Single-Sided Deafness and Asymmetric Hearing Loss: Results of a National Multicenter Study Including a Randomized Controlled Trial.

INTRODUCTION: Cochlear implantation is a recent approach proposed to treat single-sided deafness (SSD) and asymmetric hearing loss (AHL). Several cohort studies showed its effectiveness on tinnitus and variable results on binaural hearing. The main objective of this study is to assess the outcomes of cochlear implantation and other treatment options in SSD/AHL on quality of life. METHODS: This prospective multicenter study was conducted in 7 tertiary university hospitals and included an observational cohort study of SSD/AHL adult patients treated using contralateral routing of the signal (CROS) hearing aids or bone-anchored hearing systems (BAHSs) or who declined all treatments, and a randomized controlled trial in subjects treated by cochlear implantation, after failure of CROS and BAHS trials. In total, 155 subjects with SSD or AHL, with or without associated tinnitus, were enrolled. After 2 consecutive trials with CROS hearing aids and BAHSs on headband, all subjects chose any of the 4 treatment options (abstention, CROS, BAHS, or cochlear implant [CI]). The subjects who opted for a CI were randomized between 2 arms (CI vs. initial observation). Six months after the treatment choice, quality of life was assessed using both generic (EuroQoL-5D, EQ-5D) and auditory-specific quality-of-life indices (Nijmegen Cochlear implant Questionnaire [NCIQ] and Visual Analogue Scale [VAS] for tinnitus severity). Performances for speech-in-noise recognition and localization were measured as secondary outcomes. RESULTS: CROS was chosen by 75 subjects, while 51 opted for cochlear implantation, 18 for BAHSs, and 11 for abstention. Six months after treatment, both EQ-5D VAS and auditory-specific quality-of-life indices were significantly better in the "CI" arm versus "observation" arm. The mean effect of the CI was particularly significant in subjects with associated severe tinnitus (mean improvement of 20.7 points ± 19.7 on EQ-5D VAS, 20.4 ± 12.4 on NCIQ, and 51.4 ± 35.4 on tinnitus). No significant effect of the CI was found on binaural hearing results. Before/after comparisons showed that the CROS and BAHS also improved significantly NCIQ scores (for CROS: +7.7, 95% confidence interval [95% CI] = [4.5; 10.8]; for the BAHS: +14.3, 95% CI = [7.9; 20.7]). CONCLUSION: Cochlear implantation leads to significant improvements in quality of life in SSD and AHL patients, particularly in subjects with associated severe tinnitus, who are thereby the best candidates to an extension of CI indications.

Treatment choice in single-sided deafness and asymmetric hearing loss. A prospective, multicentre cohort study on 155 patients.

OBJECTIVES: To describe the treatment choice in a cohort of subjects with single-sided deafness (SSD) and asymmetric hearing loss (AHL). To assess the reliability of the treatment trials. DESIGN: In this national, multicentre, prospective study, the choice of subjects was made after two consecutive trials of Contralateral Routing Of the Signal (CROS) hearing aids and a Bone Conduction Device (BCD) on a headband. Subjects could proceed with one of these two options, opt for cochlear implantation or decline all treatments. SETTING: Seven tertiary university hospitals. PARTICIPANTS: One hundred fifty-five subjects with SSD or AHL fulfilling the candidacy criteria for cochlear implantation, with or without associated tinnitus. MAIN OUTCOME MEASURES: After the two trials, the number of subjects choosing each option was described. Repeated assessments of both generic and auditory-specific quality of life were conducted, as well as hearing assessments (speech recognition in noise and horizontal localization). RESULTS: CROS was chosen by 75 subjects, followed by cochlear implantation (n = 51), BCD (n = 18) and abstention (n = 11). Patients who opted for cochlear implantation had a poorer quality of life (P = .03). The improvement of quality of life indices after each trial was significantly associated with the final treatment choice (P = .008 for generic indices, P = .002 for auditory-specific indices). The follow-up showed that this improvement had been overestimated in the CROS group, with a long-term retention rate of 52.5%. CONCLUSIONS: More than one third of SSD/AHL subjects are unsatisfied after CROS and BCD trials. Repeated quality of life assessments help counselling the patient for his/her treatment choice.

Effects of electrode array length on frequency-place mismatch and speech perception with cochlear implants.

Frequency-place mismatch often occurs after cochlear implantation, yet its effect on speech perception outcome remains unclear. In this article, we propose a method, based on cochlea imaging, to determine the cochlear place-frequency map. We evaluated the effect of frequency-place mismatch on speech perception outcome in subjects implanted with 3 different lengths of electrode arrays. A deeper insertion was responsible for a larger frequency-place mismatch and a decreased and delayed speech perception improvement by comparison with a shallower insertion, for which a similar but slighter effect was noticed. Our results support the notion that selecting an electrode array length adapted to each individual's cochlear anatomy may reduce frequency-place mismatch and thus improve speech perception outcome.

Refining the audiological assessment in children using narrow-band CE-Chirp-evoked auditory steady state responses.

OBJECTIVE: To demonstrate the feasibility and reliability of simultaneous binaural recording of auditory steady-state responses (ASSR) in young children using narrow-band CE-Chirps as stimuli. DESIGN: Prospective cohort study comparing ASSR thresholds to four frequency stimuli (0.5, 1, 2, and 4 kHz), with click-evoked auditory brainstem responses (ABR) and behavioral response audiometry. STUDY SAMPLE: Thirty-two young children (mean age 7.4 ± 5.2 months) referred for auditory assessment were evaluated. RESULTS: The mean duration for ABR recordings was 13.3 ± 7.2 min versus 22.9 ± 15.8 min for ASSR (p < 0.01). ASSR (means of 2 and 4 kHz thresholds) were highly correlated with ABR thresholds (R2 = 0.935, p < 0.001), though significantly different (3 ± 10.7 dB, p = 0.02). ASSR (means of 0.5, 1, 2, and 4 kHz thresholds) were highly correlated with mean behavioral response audiometry thresholds (R2 = 0.968, p < 0.001). ASSRs were highly and significantly correlated with behavioral response audiometry at 0.5, 1, 2, and 4 kHz (R2 = 0.845, 0.907, 0.929, and 0.859 respectively, p < 0.001). 87.5% and 90.7% ASSR thresholds were within a ± 10 dB range around their corresponding ABR and mean behavioral response audiometry thresholds. CONCLUSIONS: Narrow-band CE-Chirps allow a fast and reliable assessment of auditory thresholds in children, especially in the low-frequency range, by comparison with other stimuli.

Value of the video head impulse test in assessing vestibular deficits following vestibular neuritis.

To evaluate the performance of the video head impulse test (VHIT) in assessing vestibular deficit in vestibular neuritis. Test validation study was conducted in Tertiary referral center. Twenty-nine patients, referred for vestibular neuritis between October 2009 and March 2012, were included. We recorded age, gender, values of caloric deficit (caloric testing), and deficits in semicircular function (VHIT) at initial presentation and at the follow-up visit (1-3 months). Multivariate linear regression analysis was performed to determine variables associated with values of caloric testing at the follow-up visit. Diagnostic values of VHIT were compared with caloric testing data using the receiver-operating characteristic (ROC) curve and subsequent statistical analysis. At the follow-up visit, complete recovery occurred in 31% of cases according to caloric evaluation, and VHIT normalized in 51.8%. Multivariate regression showed that a higher caloric deficit at the follow-up visit was associated with elevated age (p = 0.012) and high caloric deficit at initial presentation (p = 0.042). A lower caloric deficit was associated with normal VHIT results at the follow-up visit (p < 0.001). The ROC curve showed that specificity and sensitivity of VHIT were 100% when the caloric deficit was respectively lower than 40% or higher than 62.5%. At the caloric testing value of 30%, specificity was 100%, sensitivity 68.84%, positive predictive value 100% and negative predictive value 62.5%. VHIT is a fast, convenient and specific test to detect vestibular deficits in vestibular neuritis. However, VHIT lacks sensitivity by comparison with caloric testing, especially for moderate vestibular lesions.

Molecular and cellular mechanisms of loss of residual hearing after cochlear implantation.

OBJECTIVES: We describe the various molecular and cellular pathways that lead to early and delayed loss of residual hearing after cochlear implantation. METHODS: We performed a systematic review using the Medline database with the key words cochlear implant, residual hearing, inflammation, apoptosis, and necrosis. RESULTS: The mechanisms underlying the loss of residual hearing after cochlear implantation are multiple. Early hearing loss may be provoked by the surgical access to the inner ear spaces and by trauma caused by insertion of the electrode array. After the initial trauma, an acute inflammatory response promotes elevated levels of cytokines and reactive oxygen species, which in turn promote sensory cell loss by apoptosis, necrosis, and necrosis-like programmed cell death. Treatments that counteract such an inflammatory reaction, production of reactive oxygen species, and apoptosis are effective at preventing hair cell degeneration. However, delayed hearing loss appears to be a consequence of chronic inflammation with development of fibrotic tissue. The mechanisms that lead to fibrosis are poorly understood, and standard antiinflammatory drugs are insufficient for preventing its development. CONCLUSIONS: Cochlear implantation is followed by an inflammatory response involving several pathways that lead to either short-term or long-term sensory hair cell degeneration. Future studies should focus on revealing the precise molecular mechanisms induced by cochlear implantation to allow the discovery of new targets for the effective prevention and treatment of loss of residual hearing.

The transtympanic promontory stimulation test in patients with auditory deprivation: correlations with electrical dynamics of cochlear implant and speech perception.

Transtympanic promontory stimulation test (TPST) has been suggested to be a useful tool in predicting postoperative outcomes in patients at risk of poor auditory neuron functioning, especially after a long auditory deprivation. However, only sparse data are available on this topic. This study aimed at showing correlations between the auditory nerve dynamic range, evaluated by TPST, the electrical dynamic range of the cochlear implant and speech perception outcome. We evaluated 65 patients with postlingual hearing loss and no residual hearing, implanted with a Nucleus CI24 cochlear implant device for at least 2 years and with a minimum of 17 active electrodes. Using the TPST, we measured the threshold for auditory perception (T-level) and the maximum acceptable level of stimulation (M-level) at stimulation frequencies of 50, 100 and 200 Hz. General linear regression was performed to correlate 1/speech perception, evaluated using the PBK test 1 year after surgery, and 2/cochlear implant electrical dynamic range, with the age at time of implantation, the duration of auditory deprivation, the etiology of the deafness, the duration of cochlear implant use and auditory nerve dynamic range. Postoperative speech perception outcome correlated with etiology, duration of auditory deprivation and implant use, and TPST at 100 and 200 Hz. The dynamic range of the cochlear implant map correlated with duration of auditory deprivation, speech perception outcome at 6 months and TPST at 100 and 200 Hz. TPST test can be used to predict functional outcome after cochlear implant surgery in difficult cases.

European multi-centre study of the Nucleus Hybrid L24 cochlear implant.

OBJECTIVES: To investigate the preservation of residual hearing in subjects who received the Nucleus Hybrid L24 cochlear implant. To investigate the performance benefits up to one year post-implantation in terms of speech recognition, sound quality, and quality of life. DESIGN: Prospective, with sequential enrolment and within-subject comparisons. Post-operative performance using a Freedom Hybrid sound processor was compared with that of pre-operative hearing aids. STUDY SAMPLE: Sixty-six adult hearing-impaired subjects with bilateral severe-to-profound high frequency hearing loss. RESULTS: Group median increase in air-conduction thresholds in the implanted ear for test frequencies 125-1000 Hz was < 15 dB across the population; both immediately and one year post-operatively. Eighty-eight percent of subjects used the Hybrid processor at one year post-op. Sixty-five percent of subjects had significant gain in speech recognition in quiet, and 73% in noise (≥ 20 percentage points/2 dB SNR). Mean SSQ subscale scores were significantly improved (+ 1.2, + 1.3, + 1.8 points, p < 0.001), as was mean HUI3 score (+ 0.117, p < 0.01). Combining residual hearing with CI gave 22-26 %age points mean benefit in speech recognition scores over CI alone (p < 0.01). CONCLUSIONS: Useful residual hearing was conserved in 88% of subjects. Speech perception was significantly improved over preoperative hearing aids, as was sound quality and quality of life.

Effect of surgical technique on electrode impedance after cochlear implantation.

OBJECTIVES: We compare the evolution of electrode impedance values (IVs) following either conventional cochlear implantation or implantation by the soft surgery (SS) technique. METHODS: We performed a retrospective chart review of 20 consecutive adult patients who underwent implantation with the Nucleus CA 24 device between 2004 and 2007. Five patients with preoperative residual hearing at the frequencies 256, 512, and 1,024 Hz underwent implantation by an SS cochlear implantation technique (SS group), and the 15 other patients underwent a conventional implantation technique (conventional cochleostomy [CC] group). The active electrodes were classified as distal (17 to 22), middle (10 to 16), or proximal (3 to 9) according to their position in relation to the tip of the electrode array. Their IVs were collected at 1, 3, 12, 24, and 36 months after implantation. Changes in auditory thresholds at 3 and 24 months were reported for patients in the SS group. RESULTS: The postoperative IVs of both the CC and SS groups decreased significantly between 1 and 3 months after implantation (p < 0.05) and then remained stable. The IVs after 12 months were significantly lower (p < 0.05) in the SS group than in the CC group. CONCLUSIONS: Patients who underwent the SS technique displayed lower long-term electrode IVs than did their counterparts in the CC group. If electrode IVs are indeed an indirect representation of cochlear fibrosis, the use of the SS technique in lieu of the CC technique could reduce fibrotic development.

Outcomes and complications of direct end-to-side facial-hypoglossal nerve anastomosis according to the modified May technique.

OBJECT: The aim of this study was to address the efficiency and safety of direct end-to-side facial-hypoglossal nerve anastomosis for facial palsy rehabilitation. METHODS: The authors conducted a retrospective study of 12 consecutive procedures performed between December 2000 and February 2006. Facial palsies were caused by the surgical removal of tumors in the brainstem, cerebellopontine angle, or mastoid process. Direct end-to-side facial-hypoglossal anastomosis was performed in each case. Facial function (evaluated using the overall percentage of facial function and House-Brackmann scale grades), as well as tongue trophicity and mobility, were assessed at 6, 12, and 24 months after surgery. Postoperative early and late complications were systematically reviewed. RESULTS: The mean delay between tumoral and reparative surgery was 15.9 +/- 4 months (median 11 months). Preoperatively, the mean percentage facial function score was 11.6 +/- 1.7% (45% of patients with House-Brackmann Grade 5 facial palsy and 55% of patients with House-Brackmann Grade 6). Mean facial function scores increased to 19.3, 32.2, and 43.8% at 6, 12, and 24 months after surgery, respectively. Twenty-four months after surgery, 50% of cases had House-Brackmann Grade 3 facial palsy and 50% had Grade 4. A significantly better recovery at 24 months was observed postoperatively for neural lesions occurring in the mastoid or the brainstem compared with those in the cerebellopontine angle. Tongue hemiparesis was observed in 5 patients (41.7%), 2 of whom had tongue hypotrophy (16.7%). No patient complained of swallowing or speech disturbance. Facial synkinesis was noted in 1 patient (8.3%). CONCLUSIONS: Facial recovery after direct end-to-side facial-hypoglossal nerve anastomosis is similar to results observed with end-to-end or end-to-side facial-hypoglossal nerve anastomosis with an interpositional graft. Tongue hypotrophy and palsy were observed in a small number of cases. This procedure allows one to minimize, although not fully prevent, facial synkinesis. The site of the neural lesion appears to be an important factor in the prognosis of recovery.

The risks of amplified music for disc-jockeys working in nightclubs.

OBJECTIVES: Here, we evaluate the risks of amplified music for disc-jockeys (DJs) working in nightclubs. DESIGN: Sound level measurements were performed within the DJ mixing booths. A questionnaire was used to obtain exposure to noise and length of time in the profession. Audiograms and tinnitus pitch matching was also performed. RESULTS: The DJs' audiograms showed the expected noise-induced hearing loss at 6 KHz, but also low frequency losses at 125-500 Hz. Three quarters of them have tinnitus with a frequency corresponding to hearing loss. CONCLUSIONS: This study highlights the risk of amplified music on hearing and tinnitus.

Benefit of Preoperative Temporal Bone CT for Atraumatic Cochlear Implantation.

HYPOTHESIS: Evaluate the benefit of preoperative surgical planning using computed tomography (CT) for atraumatic cochlear implantation. BACKGROUND: The surgical technique has a direct impact on hearing and structure preservation. Much interest has been given to depth of electrode insertion. We focused on electrode diameter depending on exposure of round window membrane (RWM) as calculated on preoperative CT. METHODS: Measurements were calculated radiologically and anatomically on 10 temporal bones. Results were compared with CT scans of a control population. Thereafter, preoperative CT scan measurements were applied to seven additional temporal bones that underwent cochlear implantation with the insertion of two electrodes of different diameters (14 implantations) to validate radiological analysis. RESULTS: RWM size was 1.5 ±â€Š0.2 mm on CT and 1.2 ±â€Š0.2 mm during dissection; posterosuperior bony overhang of round window niche was 1.1 ±â€Š0.1 mm on CT and 1.3 ±â€Š0.2 mm during dissection. There was no statistically significant difference between radiological and anatomical measurements and between radiological measurements of cadaveric temporal bones and control population (p > 0.05 for both). Also, preoperative surgical planning was reliable in the seven temporal bones implanted with two electrode types (accuracy 93%, sensitivity 85.7%, specificity 100%) yielding no damage to intracochlear structures. CONCLUSION: Difficulties to access RWM could be predicted on preoperative CT of temporal bones and control population, which correlated well with anatomical dissections and surgical findings during cochlear implantation. According to CT planning, electrode insertion through RWM was feasible in most patients, with or without drilling posterosuperior bony overhang of round window niche. Promontory cochleostomy could be recommended when electrode apical diameter exceeded maximal RWM exposure. There was no case of intracochlear trauma on microdissections.

Ten-year follow-up of a consecutive series of children with multichannel cochlear implants.

OBJECTIVES: To assess a group of children who consecutively received implants more than 10 years after implantation with regard to speech perception, speech intelligibility, receptive language level, and academic/occupational status. STUDY DESIGN: A prospective longitudinal study. SETTING: Pediatric referral center for cochlear implantation. PATIENTS: Eighty-two prelingually deafened children received the Nucleus multichannel cochlear implant. INTERVENTIONS: Cochlear implantation with Cochlear Nucleus CI22 implant. MAIN OUTCOME MEASURES: The main outcome measures were open-set Phonetically Balanced Kindergarten word test, discrimination of sentences in noise, connective discourse tracking (CDT) using voice and telephone, speech intelligibility rating (SIR), vocabulary knowledge measured using the Peabody Picture Vocabulary Test (Revised), academic performance on French language, foreign language, and mathematics, and academic/occupational status. RESULTS: After 10 years of implant experience, 79 children (96%) reported that they always wear the device; 79% (65 of 82 children) could use the telephone. The mean scores were 72% for the Phonetically Balanced Kindergarten word test, 44% for word recognition in noise, 55.3 words per minute for the CDT, and 33 words per minute for the CDT via telephone. Thirty-three children (40%) developed speech intelligible to the average listener (SIR 5), and 22 (27%) developed speech intelligible to a listener with little experience of deaf person's speech (SIR 4). The measures of vocabulary showed that most (76%) of children who received implants scored below the median value of their normally hearing peers. The age at implantation was the most important factor that may influence the postimplant outcomes. Regarding educational/vocational status, 6 subjects attend universities, 3 already have a professional activity, 14 are currently at high school level, 32 are at junior high school level, 6 additional children are enrolled in a special unit for children with disability, and 3 children are still attending elementary schools. Seventeen are in further noncompulsory education studying a range of subjects at vocational level. CONCLUSION: This long-term report shows that many profoundly hearing-impaired children using cochlear implants can develop functional levels of speech perception and production, attain age-appropriate oral language, develop competency level in a language other than their primary language, and achieve satisfactory academic performance.

Cone-beam computed tomography in children with cochlear implants: The effect of electrode array position on ECAP.

OBJECTIVES: To assess the feasibility of using cone-beam computed tomography (CBCT) in young children with cochlear implants (CIs) and study the effect of intracochlear position on electrophysiological and behavioral measurements. METHODS: A total of 40 children with either unilateral or bilateral cochlear implants were prospectively included in the study. Electrode placement and insertion angles were studied in 55 Cochlear® implants (16 straight arrays and 39 perimodiolar arrays), using either CBCT or X-ray imaging. CBCT or X-ray imaging were scheduled when the children were leaving the recovery room. We recorded intraoperative and postoperative neural response telemetry threshold (T-NRT) values, intraoperative and postoperative electrode impedance values, as well as behavioral T (threshold) and C (comfort) levels on electrodes 1, 5, 10, 15 and 20. RESULTS: CBCT imaging was feasible without any sedation in 24 children (60%). Accidental scala vestibuli insertion was observed in 3 out of 24 implants as assessed by CBCT. The mean insertion angle was 339.7°±35.8°. The use of a perimodiolar array led to higher angles of insertion, lower postoperative T-NRT, as well as decreased behavioral T and C levels. We found no significant effect of either electrode array position or angle of insertion on electrophysiological data. CONCLUSION: CBCT appears to be a reliable tool for anatomical assessment of young children with CIs. Intracochlear position had no significant effect on the electrically evoked compound action potential (ECAP) threshold. Our CBCT protocol must be improved to increase the rate of successful investigations.

Characteristics of tinnitus in a population of 555 patients: specificities of tinnitus induced by noise trauma.

Tinnitus is often associated with hearing loss of a known etiology. In this study, we compared tinnitus that appeared to be induced by noise trauma with that perceived to start in other circumstances in a population of 555 patients attending the specialist tinnitus clinic at the University Hospital in Montpellier, France. Patients had consulted for persistent tinnitus for 7 years from the onset of their symptoms. Among these tinnitus patients, 17% described their tinnitus as starting after excessive noise exposure. The patients who had a history of noise trauma had a symmetrical hearing loss, and no difference was seen in lateralization of tinnitus perception. This subset of patients was mainly male and on average was 10 years younger than other tinnitus patients. In this population, the hearing loss is significantly less than that measured in the other patients, even allowing for their younger age. Statistical analysis showed a significant correlation between a history of exposure to noise trauma and the presence of a high-pitched "whistling" tinnitus. The presence of whistling tinnitus was significantly correlated with high-frequency hearing loss. The intensity of tinnitus, measured using a visual analog scale, appeared to be stronger than the measured hearing loss would suggest.

Outcomes after cochlear reimplantation in children.

OBJECTIVES: With cochlear implantation now a routine procedure, reimplantation is becoming more commonplace for medical/surgical complications or device malfunctions. This study investigated the indications for reimplantation and the auditory outcomes following reimplantation surgery in prelingually-deafened children. METHODS: Of the 539 prelingually deafened children implanted between 1990 and 2013, 45 were reimplanted (8.3% of implantations). Causes of reimplantation, type of device and angle of insertion at initial implantation were recorded, as well as type of implant reinserted, number of electrodes inserted and angle of insertion (calculated on cone beam computed tomography) on reimplantation, and finally any surgical findings. Speech perception test scores (phonetically balanced kindergarten (PBK) words, open-set sentence testing in quiet and in noise (S/N+ 10 dB SNR), and speech tracking scores) were obtained 1, 2 and 3 years after reimplantation, and compared against the best speech recognition score obtained with the first implant before failure. RESULTS: Medical reasons for reimplantation were found in 10 cases (22.2%). A malfunctioning device had occurred in 35 cases (77.7%) including hard failure in 24 and soft failure in 11. Complete insertion was achieved in the scala tympani in 42 cases and in the scala vestibuli in one case; partial insertion occurred in the remaining two cases. In two cases, one or two electrode rings snatched off from the electrode array during removal. The mean insertion angle was 330.5° before surgery and 311.8° after reimplantation (no statistical difference p=0.48). The postoperative speech perception outcome measures showed no significant difference to the best score before reimplantation. Angle of insertion, type of device and etiology of deafness did not influence the results. The PBK performance improved over 10% in 43.2% of children, was similar in 40.5%, and showed a more than 10% decrease in 16.2% of children after reimplantation. The latter decline in performance was explained for some children by a partial insertion. CONCLUSIONS: Reimplantation has no negative effect on auditory outcome. In rare cases, speech perception outcome may not improve, requiring a specific rehabilitation program.

Modeling of Auditory Neuron Response Thresholds with Cochlear Implants.

The quality of the prosthetic-neural interface is a critical point for cochlear implant efficiency. It depends not only on technical and anatomical factors such as electrode position into the cochlea (depth and scalar placement), electrode impedance, and distance between the electrode and the stimulated auditory neurons, but also on the number of functional auditory neurons. The efficiency of electrical stimulation can be assessed by the measurement of e-CAP in cochlear implant users. In the present study, we modeled the activation of auditory neurons in cochlear implant recipients (nucleus device). The electrical response, measured using auto-NRT (neural responses telemetry) algorithm, has been analyzed using multivariate regression with cubic splines in order to take into account the variations of insertion depth of electrodes amongst subjects as well as the other technical and anatomical factors listed above. NRT thresholds depend on the electrode squared impedance (ß = -0.11 ± 0.02, P < 0.01), the scalar placement of the electrodes (ß = -8.50 ± 1.97, P < 0.01), and the depth of insertion calculated as the characteristic frequency of auditory neurons (CNF). Distribution of NRT residues according to CNF could provide a proxy of auditory neurons functioning in implanted cochleas.

Manual Electrode Array Insertion Through a Robot-Assisted Minimal Invasive Cochleostomy: Feasibility and Comparison of Two Different Electrode Array Subtypes.

HYPOTHESIS: To evaluate the feasibility and the results of insertion of two types of electrode arrays in a robotically assisted surgical approach. BACKGROUND: Recent publications demonstrated that robot-assisted surgery allows the implantation of free-fitting electrode arrays through a cochleostomy drilled via a narrow bony tunnel (DCA). We investigated if electrode arrays from different manufacturers could be used with this approach. METHODS: Cone-beam CT imaging was performed on five-cadaveric heads after placement of fiducial screws. Relevant anatomical structures were segmented and the DCA trajectory, including the position of the cochleostomy, was defined to target the center of the scala tympani while reducing the risk of lesions to the facial nerve. Med-El Flex 28 and Cochlear CI422 electrodes were implanted on both sides, and their position was verified by cone-beam CT. Finally, temporal bones were dissected to assess the occurrence of damage to anatomical structures during DCA drilling. RESULTS: The cochleostomy site was directed in the scala tympani in 9 of 10 cases. The insertion of electrode arrays was successful in 19 of 20 attempts. No facial nerve damage was observed. The average difference between the planned and the postoperative trajectory was 0.17 ± 0.19 mm at the level of the facial nerve. The average depth of insertion was 305.5 ± 55.2 and 243 ± 32.1 degrees with Med-El and Cochlear arrays, respectively. CONCLUSIONS: Robot-assisted surgery is a reliable tool to allow cochlear implantation through a cochleostomy. Technical solutions must be developed to improve the electrode array insertion using this approach.

Modeling the relationship between psychophysical perception and electrically evoked compound action potential threshold in young cochlear implant recipients: clinical implications for implant fitting.

OBJECTIVE: In cochlear implant recipients, the threshold of the electrically evoked compound action potential (ECAP) has been shown to correlate with the perceptual detection threshold and maximum comfortable loudness levels (respectively, T- and C-levels) used for implant programming. Our general objective was to model the relationship between ECAP threshold and T/C-levels by taking into account their relative changes within each subject. In particular, we were interested in investigating further the validity of ECAP threshold as a predictor of psychophysical levels, depending on intra-cochlear electrode location and time of testing (from 1 to 18 months post-implantation). METHODS: A total of 370 ECAP thresholds, measured in 49 children, using a Nucleus 24 cochlear implant, were compared with the corresponding T- and C-levels obtained at the same visit, for the same electrode. Response profiles for the whole group of patients were modeled across four test electrodes spaced equally along the electrode array from base towards apex. A linear regression model was constructed and the quality of the ECAP threshold-based predictions was assessed by testing for correlation between measured and predicted psychophysics. Comparison was made with a more simplistic model (described here as the 'parallel profiles method') stipulating, within each subject, a 1 microA increase in psychophysical levels for every 1 microA increase in ECAP threshold. RESULTS: Offset between ECAP threshold and psychophysics profiles was found to vary significantly along the electrode array for the T-, but not for the C-level. In contrast with the parallel profiles method, our regression model predicted, within each subject, an average increase of 0.23 microA (95% confidence interval: 0.18-0.28) in T-level for every 1 microA increase in ECAP threshold. This correction improved the quality of T-level prediction when our model was run using measured T-level and ECAP threshold from a reference electrode (r=0.77 vs. r=0.62). The shorter the distance between the electrode for which T-level was predicted and the one used as reference, the stronger the correlation between measured and predicted T-levels. In addition, poorer T-level predictions were obtained at the basal end of the array during the first 3 months post-implantation. In contrast to T-level, individual changes in C-level with ECAP threshold exhibited heterogeneous patterns across subjects so that no common coefficient could account for these changes. However, applying the parallel profiles method led to high-quality C-level prediction. CONCLUSIONS AND SIGNIFICANCE: The results suggest that covariation between ECAP thresholds and psychophysics plays a decisive role in the relationship of ECAP threshold with T-, but not with C-level. Therefore, our regression model and the parallel profiles method should both be used for predicting, respectively, the T- and the C-levels. Although the predictability of our regression model seems to be better for middle and apical electrodes, its utilization should be extended to basal electrodes after 6 months' implant use.

Rehabilitation for high-frequency sensorineural hearing impairment in adults with the symphonix vibrant soundbridge: a comparative study.

OBJECTIVE: To assess and compare the benefits for patients with high-frequency hearing loss obtained from an implantable middle ear implant, the Symphonix Vibrant Soundbridge using the SIGNIA processing circuitry, to those derived from conventional amplification using the same integrated circuitry and to those derived from a variety of preoperatively worn hearing aids. STUDY DESIGN: A single-subject, repeated-measures study design was used for a comparative evaluation of the benefits derived from the Symphonix Vibrant Soundbridge and conventional amplification. Objective audiometric measures were performed postoperatively to compare the Symphonix Vibrant Soundbridge (404) and SIGNIA hearing aid, both using the SIGNIA processing chip. Tests were performed under three conditions: unaided, aided Symphonix Vibrant Soundbridge (404), and aided SIGNIA hearing aid. Subjective self-assessment scales, standardized and nonstandardized, were completed for the Symphonix Vibrant Soundbridge (404) and the preoperative hearing aid to compare the personally perceived benefits. Statistical comparison of the data sets with each device type was performed using the nonparametric Wilcoxon test. SETTING: One tertiary teaching hospital and one hearing aid specialist fitting office. SUBJECTS: Six patients displaying a high-frequency hearing loss who had the Symphonix Vibrant Soundbridge implanted for an average of 17 months. INTERVENTION: Rehabilitative. RESULTS: Aided thresholds with the Symphonix Vibrant Soundbridge (404) and the SIGNIA hearing aid showed no significant difference. Speech comprehension scores in quiet and in noise were significantly improved with each device type over the unaided condition scores. Individual performance on speech test measures was equivalent or superior with the Symphonix Vibrant Soundbridge (404) in comparison with that with the SIGNIA hearing aid. When using the Symphonix Vibrant Soundbridge (404) in quiet, the group achieved 50% speech comprehension at significantly softer presentation levels (p = 0.027) than when wearing the SIGNIA hearing aid. Similarly, in noise, 50% speech comprehension was achieved at significantly lower (more difficult) signal-to-noise ratios (p = 0.028) with the Symphonix Vibrant Soundbridge (404) than with the SIGNIA hearing aid. The level of satisfaction for various aspects of the device and performance and listening ease, particularly in the presence of aversive sounds and in reverberant conditions, was reported as significantly better with the Symphonix Vibrant Soundbridge (404) than with the preoperative hearing aid. CONCLUSIONS: Despite similar gain with each device type using the same SIGNIA processing technology, the patient group demonstrated significant advantages for speech comprehension in quiet and in noise when using the Symphonix Vibrant Soundbridge (404). Such an effect may be attributed to higher fidelity sound transmission by means of the direct-drive mechanism used by the implant. Subjective reports support the results from the objective assessments, both being in favor of the implant over conventional amplification. In conclusion, the Symphonix Vibrant Soundbridge (404) is a suitable treatment option offering advantages over conventional amplification to the hearing-impaired person with a high-frequency hearing loss.