H.E. Cullington

Normative Findings of Electrically Evoked Compound Action Potential Measurements Using the Neural Response Telemetry of the Nucleus CI24M Cochlear Implant System

One hundred and forty-seven adult recipients of the Nucleus® 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedure. Recordings were obtained in 96% of these subjects with this standardised procedure. The group results are presented in terms of peak amplitude and latency, slope of the amplitude growth function and ECAP threshold. The effects of aetiological factors and the duration of deafness on the ECAP were also studied. While large intersubject variability and intrasubject variability (across electrodes) were found, results fell within a consistent pattern and a normative range of peak amplitudes and latencies was established. The aetiological factors had little effect on the ECAP characteristics. However, age affected ECAP amplitude and slope of the amplitude growth function significantly; i.e., the amplitude is higher in the lowest age category (15–30 years). Principal component analysis of the ECAP thresholds shows that the thresholds across 5 electrodes can be described by two factors accounting for 92% of the total variance. The two factors represent the overall level of the threshold profiles (‘shift’) and their slopes across the electrode array (‘tilt’). Correlation between these two factors and the same factors describing the T- and C-levels appeared to be moderate, in the range of 0.5–0.6.

Speech recognition with varying numbers and types of competing talkers by normal-hearing, cochlear-implant, and implant simulation subjects.

Cochlear-implant users perform far below normal-hearing subjects in background noise. Speech recognition with varying numbers of competing female, male, and child talkers was evaluated in normal-hearing subjects, cochlear-implant users, and normal-hearing subjects utilizing an eight-channel sine-carrier cochlear-implant simulation. Target sentences were spoken by a male. Normal-hearing subjects obtained considerably better speech reception thresholds than cochlear-implant subjects; the largest discrepancy was 24 dB with a female masker. Evaluation of one implant subject with normal hearing in the contralateral ear suggested that this difference is not caused by age-related disparities between the subject groups. Normal-hearing subjects showed a significant advantage with fewer competing talkers, obtaining release from masking with up to three talker maskers. Cochlear-implant and simulation subjects showed little such effect, although there was a substantial difference between the implant and simulation results with talker maskers. All three groups benefited from a voice pitch difference between target and masker, with the female talker providing significantly less masking than the male. Child talkers produced more masking than expected, given their fundamental frequency, syllabic rate, and temporal modulation characteristics. Neither a simulation nor testing in steady-state noise predicts the difficulties cochlear-implant users experience in real-life noisy situations.

Bimodal hearing benefit for speech recognition with competing voice in cochlear implant subject with normal hearing in contralateral ear.

Objectives: This project assessed electroacoustic benefit for speech recognition with a competing talker. Design: Using a cochlear implant subject with normal hearing in the contralateral ear, the contribution of low-pass and high-pass natural sound to speech recognition was systematically measured. Results: High-frequency sound did not improve performance, but low-frequency sound did, even when unintelligible and limited to frequencies below 150 Hz. Conclusions: The low-frequency sound assists separation of the two talkers, presumably using the fundamental frequency cue. Extrapolating this finding to regular cochlear implant users may suggest that using a hearing aid on the contralateral ear will improve performance, even with limited residual hearing.

An investigation into the effect of limiting the frequency bandwidth of speech on speech recognition in adult cochlear implant users

The purpose of this study was to investigate the effect of the limited-frequency bandwidth employed by telephones (300-3400 Hz) on speech recognition in adult cochlear implant users. The Four Alternative Auditory Feature (FAAF) test was used in four conditions: unfiltered and in three filtered conditions of 300-4500 Hz, 300-3400 Hz and 300-2500 Hz. Ten subjects implanted with the Nucleus CI24M device and 10 normal-hearing listeners were assessed to examine differences between word discrimination scores in each condition. Scores obtained from the 300-3400-Hz and 300-2500-Hz filtered conditions were significantly worse than those with unfiltered speech for the cochlear implant subjects, decreasing by 17.7% and 21.4%, respectively, from scores with unfiltered speech. By contrast, the normal-hearing listeners did not experience difficulties in discriminating between words in any of the conditions. Analysis of the word errors demonstrated that the reduction in implant subject scores with bandwidth arose from errors in place of articulation. Filtering speech in this way has a significant effect on speech recognition for cochlear implant subjects but not normal-hearing listeners. Hence, the limitations of the normal telephone bandwidth can be expected to have a negative effect on speech recognition for cochlear implant users using the telephone. Sumario El objetivo de este estudio fue investigar los efectos de la banda de frecuencia limitada que utilizan los tele´fonos (300-3400 Hz) en el reconocimiento del lenguaje en adultos con implante coclear. Se utilizo´ la prueba de cuatro caracteri´sticas auditivas alternativas (FAAF) en cuatro diferentes condiciones: sin filtro y con tres modalidades de filtracio´n: 300-4500 Hz, 300-3400 Hz y 300-2500 Hz. Se evaluaron diez sujetos implantados con el Nucleus C124M y 10 sujetos normales para conocer las diferencias en la puntuacio´n de discriminacio´n de la palabra en cada condicio´n. La puntuacio´n obtenida de la filtracio´n a 300-3400 Hz y a 300-2500 Hz fueron significativamente peores que aquellas sin filtracio´n en los sujetos implantados, con un decremento del 17.7% y 21.4% respectivamente a partir de la puntuacio´n de la condicio´n sin filtro. En contraste, los sujetos normales no mostraron dificultades en la discriminacio´n de palabras en ninguna de las condiciones. El ana´lisis de los errores cometidos demostro´ que la reduccio´n de las puntuaciones en los sujetos implantados fue en el punto de articulacio´n. Esta filtracio´n del lenguaje tiene un efecto significativo en el reconocimiento del lenguaje en los sujetos con implante coclear, pero no asi´ en los sujetos con audicio´n normal. Por lo tanto, es de esperar que la limitacio´n del ancho de banda de los tele´fonos tenga un efecto negativo en el reconocimiento del lenguaje en los implantados que utilizan el tele´fono.

Cochlear Implant Programming: A Global Survey on the State of the Art

The programming of CIs is essential for good performance. However, no Good Clinical Practice guidelines exist. This paper reports on the results of an inventory of the current practice worldwide. A questionnaire was distributed to 47 CI centers. They follow 47600 recipients in 17 countries and 5 continents. The results were discussed during a debate. Sixty-two percent of the results were verified through individual interviews during the following months. Most centers (72%) participated in a cross-sectional study logging 5 consecutive fitting sessions in 5 different recipients. Data indicate that general practice starts with a single switch-on session, followed by three monthly sessions, three quarterly sessions, and then annual sessions, all containing one hour of programming and testing. The main focus lies on setting maximum and, to a lesser extent, minimum current levels per electrode. These levels are often determined on a few electrodes and then extrapolated. They are mainly based on subjective loudness perception by the CI user and, to a lesser extent, on pure tone and speech audiometry. Objective measures play a small role as indication of the global MAP profile. Other MAP parameters are rarely modified. Measurable targets are only defined for pure tone audiometry. Huge variation exists between centers on all aspects of the fitting practice.

Preliminary neural response telemetry results

Abstract This paper describes the neural response telemetry (NRT) results obtained from the first 30 patients tested at this centre. One hundred per cent of patients tested intra-operatively had NRT responses on at least one electrode; this compared to 82.4% of patients tested post-operatively. Reasonable correlations existed between post-operative NRT thresholds and psychophysical threshold and comfort levels, although there was too much variability for the data to be used to set these parameters directly. Post-operative NRT thresholds were always at levels audible to patients.

Comparison of language ability in children with cochlear implants placed in oral and total communication educational settings

INTRODUCTION Previous research has demonstrated that children with cochlear implants placed in oral educational settings have significantly better speech perception abilities than those in total communication environments. However, one important goal of pédiatrie implantation is linguistic development, and speech perception ability does not necessarily reflect this. This study examines and compares the linguistic abilities of young implant recipients in oral and total communication settings.

Cochlear Implants: Objective Measures

The age at which children are receiving cochlear implants has dropped dramatically; some children now undergo surgery when less than 12 months old. Considerable feedback is required from the patient in order to set the device optimally. This can be difficult in very young children, who may be unable to provide any behavioral information. It is therefore vital that objective measures are available in order to evaluate the device and auditory system function, set the programming parameters, and even assess performance. This book covers cochlear implant objective measures used before, during and after surgery. It provides a handbook for clinicians detailing the many techniques currently used, including telemetry, averaged electrode voltages, and electrically–evoked stapedial reflexes, auditory brainstem responses, compound action potentials, middle, late and event–related potentials. The internationally respected chapter authors from Europe and the USA provide coverage of the objective measures used in several commercially available cochlear implant devices. This book is required reading for clinicians in cochlear implant centers, researchers and those in the commercial implant field worldwide

Tinnitus evoked by finger movement: Brain plasticity after peripheral deafferentation

Tinnitus, the sensation of sound in the absence of external acoustic stimuli, is a common problem. Most patients with tinnitus have no control over the loudness or characteristics of their tinnitus; however, a few individuals can alter their tinnitus voluntarily by moving parts of their bodies. The rare phenomenon of gaze-evoked tinnitus1 describes the ability to control tinnitus using eye movements; in total, 17 cases have been reported. Even more rare, two patients experienced cutaneous-evoked tinnitus2; they could control their tinnitus by touching either their fingers or the top of their hand. In all reported patients except one, gaze-evoked or cutaneous-evoked tinnitus occurred following unilateral surgical deafferentation of the auditory periphery after removal of space-occupying lesions of the cerebellopontine angle. One gaze-evoked tinnitus case involved a patient with a meningeal metastasis of a malignant melanoma3; this woman could …

Cochlear implantation of a deaf blind patient with mitochondrial cytopathy

Genetic defects of the mitochondrial DNA often cause sensorineural hearing impairment, accompaniment by disorders of organs within the body. This case report describes cochlear implantation of a 33-year-old deaf blind female with mitochondrial cytopathy. The outcome was very successful, and vastly improved quality of life for this patient. Many cases of mitochondrial cytopathy cause progressive deafness; it is, therefore, likely that other patients with this unusual disorder will present for cochlear implant assessment.