Chris James

Preservation of residual hearing with cochlear implantation: how and why.

Conclusions Hearing may be conserved in adults after implantation with the Nucleus Contour Advance perimodiolar electrode array. The degree of hearing preservation and the maximum insertion depth of the electrode array can vary considerably despite a defined surgical protocol. Residual hearing combined with electrical stimulation in the same ear can provide additional benefits even for conventional candidates for cochlear implantation. Objectives We present preliminary results from a prospective multicentre study investigating the conservation of residual hearing after implantation with a standard-length Nucleus Contour Advance perimodiolar electrode array and the benefits of combined electrical and acoustic stimulation. Material and methods The subjects were 12 adult candidates for cochlear implantation recruited according to national selection criteria. A “soft” surgery protocol was defined, as follows: 1–1.2-mm cochleostomy hole anterior and inferior to the round window; Nucleus Contour Advance electrode array inserted using the “Advance-off-stylet” technique; and insertion depth controlled by means of three square marker ribs left outside the cochleostomy hole. These procedures had been shown to reduce insertion forces in temporal bone preparations. Variations in surgical techniques were monitored using a questionnaire. Pure-tone thresholds were measured pre- and postoperatively. Patients who still retained thresholds <90 dB HL for frequencies up to 500 Hz were re-fitted with an in-the-ear (ITE) hearing aid. Word recognition was tested in quiet and sentence perception in noise for the cochlear implant alone and in combination with an ipsilateral hearing aid. Results Hearing threshold level data were available for 12 patients recruited from 6 of the centres. Median increases in hearing threshold levels were 23, 27 and 33 dB for the frequencies 125, 250 and 500 Hz, respectively. These median increases include the data for two patients who had total loss of residual hearing due to difficulties encountered during surgery. “Cochlear view” X-ray images indicated that the depth of insertion varied between 300 and 430°, despite modest variations in the length of the electrode inserted (17–19 mm). The insertion angle had some influence on the preservation of residual hearing at frequencies of 250–500 Hz. Six of the 12 patients retained sufficient hearing for effective use of an ipsilateral ITE hearing aid (≤80 dB HL at 125 and 250 Hz; ≤90 dB HL at 500 Hz). Word recognition scores in quiet were improved from 10% to 30% with the cochlear implant plus ipsilateral hearing aid in 3 patients who had at least 3 months postoperative experience. Signal:noise ratio thresholds for sentence recognition were improved by up to 3 dB. Patients reported that they experienced greatly improved sound quality and preferred to use the two devices together.

Partial Deafness Treatment with the Nucleus Straight Research Array Cochlear Implant

Introduction: The Nucleus Straight Research Array (SRA) cochlear implant has a new 25-mm electrode carrier designed to minimize insertion trauma, in particular allowing easy insertion via the round window. The aims of this study were to measure preoperative to postoperative benefit in terms of speech recognition in quiet and in noise in three groups of patients (electrical complement, EC; electrical stimulation, ES; electro-acoustic stimulation, EAS) with varying levels of low-frequency hearing, and to evaluate the preservation of residual hearing after implantation with the SRA cochlear implant. Methods: The study design was prospective with sequential enrolment and within-subject comparisons: 23 adult cochlear implant candidates were divided into three groups according to their level of preoperative residual hearing at 500 Hz (EC ≤50 dB; 50 dB < EAS < 80 dB; ES ≧80 dB). Monosyllabic word recognition using the SRA cochlear implant in combination with residual low-frequency hearing was assessed at 4 and 13 months after implantation. Hearing threshold levels were also monitored over time. Results: Subjects across all three groups had significant improvements in speech recognition scores (i.e. >20 percentage points) both for listening in quiet (71% of subjects) and in noise (100% of subjects). The average score at 4 months after operation for words presented in quiet was 61.7%, and in 10 dB SNR noise 46.5%, compared to 34.4 and 10.6% preoperatively (p < 0.001). All subjects retained measurable hearing at 500 Hz in the implanted ear at 4 months after the operation; mean increases were 19, 29 and 1 dB for the EC, EAS and ES groups (n = 21). Across frequencies of 125–1000 Hz, the median increase in thresholds was 15 dB up to 13 months postoperatively (n = 15). Conclusions: Speech recognition performance of subjects with various levels of residual low-frequency hearing was significantly improved with the SRA cochlear implant. A high level and rate of hearing preservation was achieved with the SRA implanted using a round window surgical technique. Subjects with preoperative low-frequency hearing levels between 50 and 80 dB HL (EAS group) tended to lose more hearing than those with either better or worse hearing.

Reliability of cone beam computed tomography in scalar localization of the electrode array: a radio histological study

Postoperative imaging plays a growing role in clinical studies concerning prognostic factors in cochlear implantation. Indeed, intracochlear position of the cochlear implant has recently been identified as a contributor in functional outcomes and radiological tools must be accurate enough to determine the final placement of the electrode array. The aim of our study was to validate cone beam computed tomography as a reliable technique for scalar localization of the electrode array. We performed therefore a temporal bone study on ten specimens that were implanted with a perimodiolar implant prototype. Cone beam reconstructions were performed and images were analyzed by two physicians both experienced in cochlear implant imaging, who determined the scalar localization of the implant. Temporal bones then underwent histological control to document this scalar localization and hypothetical intracochlear lesions. In four cases, a dislocation from scala tympani to scala vestibuli was suspected on cone beam reconstructions of the ascending part of the basal turn. In three of these four specimens, dislocation in pars ascendens was confirmed histologically. In the remaining temporal bone, histological analysis revealed an elevation with rupture of the basilar membrane. Histological assessment revealed spiral ligament tearing in another bone. We conclude that cone beam is a reliable tool to assess scalar localization of the selectrode array and may be used in future clinical studies.

Voice discrimination in cochlear-implanted deaf subjects

The human voice is important for social communication because voices carry speech and other information such as a persons physical characteristics and affective state. Further restricted temporal cortical regions are specifically involved in voice processing. In cochlear-implanted deaf patients, the processor alters the spectral cues which are crucial for the perception of the paralinguistic information of human voices. The aim of this study was to assess the abilities of voice discrimination in cochlear-implant (CI) users and in normal-hearing subjects (NHS) using a CI simulation (vocoder). In NHS the performance in voice discrimination decreased when reducing the spectral information by decreasing the number of channels of the vocoder. In CI patients with different delays after implantation we observed a strong impairment in voice discrimination at time of activation of the neuroprosthesis. No significant improvement can be detected in patients after two years of experience of the implant while they have reached a higher level of recovery of speech perception, suggesting a dissociation in the dynamic of functional recuperation of speech and voice processing. In addition to the lack of spectral cues due to the implant processor, we hypothesized that the origin of such deficit could derive from a crossmodal reorganization of the temporal voice areas in CI patients.

Conversion of adult Nucleus® 5 cochlear implant users to the Nucleus® 6 system

Abstract Objectives Cochlears new sound processor system (Nucleus® 6) features a new noise reduction algorithm called SNR-NR (signal-to-noise ratio), and an environmental classifier called SCAN, which activates the appropriate sound coding algorithms for a given listening environment. In addition, the sound processors (CP910 and CP920) have a data logging feature with data visually summarized using clinical programing software and come with two remote controls, CR210 and CR230. The objective of this clinical study was to conduct a field acceptance study comparing the user experience with the Nucleus® 6 to the Nucleus® 5 system and to evaluate the benefits of Nucleus® 6 in an adult population currently equipped with the previous generation Nucleus® 5 sound processor. Our primary objective was to compare speech recognition in speech-weighted noise using Nucleus® 6 with SCAN (activating SNR-NR) with the default Nucleus® 5 ‘Noise’ Program. Secondary objectives included comparisons of speech recognition in quiet, subjective performance feedback via questionnaires and diaries, and recipient preference for device and program type. Methods A prospective controlled trial was conducted with 30 adult Nucleus CI recipients using the Nucleus® 5 sound processor (condition A). The Nucleus® 6 sound processor (condition B) was evaluated in a within-subject ABBA design, with repeated speech in noise (S0N0, LIST sentence test), and speech in quiet testing (S0, NVA words). The remote controls were randomly given during the two B intervals. In addition, recipients had to complete questionnaires and diaries on the use of their current as well as new sound processors and remotes. Results The group mean speech reception threshold in noise (SRT50) with Nucleus® 6 SCAN was significantly better (1.2 dB SNR) than with the Nucleus® 5 ‘Noise’ Program. Mean speech recognition scores in quiet were not significantly different between the processors. Subjective performance feedback (APHAB) did not show a significant difference between Nucleus® 6 and Nucleus® 5 with high satisfaction scores being reported for both sound processors. Recipients preferred the SCAN program in noise and reported a clear overall preference for the Nucleus® 6 system. Clinicians were satisfied with the conversion process from Nucleus® 5 to Nucleus® 6. Discussion and conclusion SNR-NR provides a significant benefit in noise. Recipients were easily converted from Nucleus® 5 to Nucleus® 6 requiring little or no sound quality adjustment period. The Nucleus® 6 SCAN program was well accepted by the majority of recipients for use during their daily life.

The effects of sound coder carrier rate and modulation bandwidth on voice pitch perception in cochlear implant users

We employed the dual filter-bank “STEP” coder to separately control the spectral and temporal modulation resolution of analysis channels. Previously we compared vowel pitch ranking and gender classification with eight subjects using enhanced modulation at F0—including across-channel synchronised modulation to the ACE coder. There was no significant improvement using modulation enhanced coding versus ACE across subjects. In a follow-up experiment we looked at the effect of stimulation rate on voice pitch perception. Since there are large inter-subject differences in overall temporal pitch acuity we hypothesised that some subjects’ performance may be more greatly influenced by carrier rate than others, or that some subjects may find sound quality satisfactory with lower carrier rates than those in their clinical processors. We used a version of STEP with a very short temporal envelope analysis window of 2 ms which allows a very low latency real-time processing implementation and large maximum modulation bandwidth. Subjects were tested using carrier rates of 1000, 500 and 250 pps/ch with modulation bandwidths controlled via low-pass filtering. Pilot data indicated that the new low-latency coder provides very good sound quality compared to ACE using 1000 pps/ch or 500 pps/ch. Also the modulation bandwidth could be tuned at different carrier rates to optimize voice pitch perception based on temporal cues. This opens the potential for lower stimulation rates to be used in CI coding while maintaining optimal temporal resolution.We employed the dual filter-bank “STEP” coder to separately control the spectral and temporal modulation resolution of analysis channels. Previously we compared vowel pitch ranking and gender classification with eight subjects using enhanced modulation at F0—including across-channel synchronised modulation to the ACE coder. There was no significant improvement using modulation enhanced coding versus ACE across subjects. In a follow-up experiment we looked at the effect of stimulation rate on voice pitch perception. Since there are large inter-subject differences in overall temporal pitch acuity we hypothesised that some subjects’ performance may be more greatly influenced by carrier rate than others, or that some subjects may find sound quality satisfactory with lower carrier rates than those in their clinical processors. We used a version of STEP with a very short temporal envelope analysis window of 2 ms which allows a very low latency real-time processing implementation and large maximum modulation ban...

Speech-in-noise perception in unilateral hearing loss: Relation to pure-tone thresholds and brainstem plasticity

&NA; We investigated speech recognition in noise in subjects with mild to profound levels of unilateral hearing loss. Thirty‐five adults were evaluated using an adaptive signal‐to‐noise ratio (SNR50) sentence recognition threshold test in three spatial configurations. The results revealed a significant correlation between pure‐tone average audiometric thresholds in the poorer ear and SNR thresholds in the two conditions where speech and noise were spatially separated: dichotic – with speech presented to the poorer ear and reverse dichotic – with speech presented to the better ear. This first result suggested that standard pure‐tone air‐conduction thresholds can be a reliable predictor of speech recognition in noise for binaural conditions. However, a subgroup of 14 subjects was found to have poorer‐than‐expected speech recognition scores, especially in the reverse dichotic listening condition. In this subgroup 9 subjects had been diagnosed with vestibular schwannoma at stage III or IV likely affecting the lower brainstem function. These subjects showed SNR thresholds in the reverse dichotic condition on average 4 dB poorer (higher) than for the other 21 normally‐performing subjects. For the 7 of 9 subjects whose vestibular schwannoma was removed, the deficit was no longer apparent on average 5 months following the surgical procedure. These results suggest that following unilateral hearing loss the capacity to use monaural spectral information is supported by the lower brainstem. HighlightsSubjects with mild to total unilateral hearing loss were evaluated with both the Matrix test and clinical audiometries.Pure‐tone air conduction can be a reliable predictor for binaural hearing evaluation.Vestibular schwannoma stage III or IV may affect the lower brainstem structure and creates binaural hearing distortions.A surgical schwannoma removal may allowed monaural spectral remapping.

Réhabilitation des surdités profondes unilatérales de l’adulte : système CROS, implant à ancrage osseux ou implant cochléaire ?

Résultats.— Onze patients (six femmes : 47 ± 12 ans) furent implantés en utilisant la technique du punch et comparés à 7 cas opérés par technique linéaire classique (Nijmegen — cinq femmes : 59 ± 9 ans). L’âge moyen de la population totale était de 52 ± 12 ans. Une ostéointégration fut obtenue dans tous les cas. La mise en route de la BAHA était autorisée à partir de j15 en dehors de complications. Huit cas sur les 11 opérés avec la technique du punch (72,7 %) eurent des suites simples. Trois cas durent être repris en salle opératoire pour parage cutané sous-anesthésie locale. Aucun cas de recouvrement de pilier ne fut constaté. Par comparaison, deux cas sur les sept opérés par technique linéaire eurent des suites compliquées. La différence entre les deux séries n’était pas significative. Aucun des patients opérés avec la technique du punch n’eut de troubles sensitifs cutanés. Conclusion.— La technique d’implantation de pilier ostéo-intégré pour prothèse de type BAHA est une simplification conséquente de l’acte chirurgical menant aux mêmes résultats postopératoires que la technique linéaire, et n’entraînant pas de troubles sensitifs périprothétiques.