René H. Gifford

The Benefits of Combining Acoustic and Electric Stimulation for the Recognition of Speech, Voice and Melodies

Fifteen patients fit with a cochlear implant in one ear and a hearing aid in the other ear were presented with tests of speech and melody recognition and voice discrimination under conditions of electric (E) stimulation, acoustic (A) stimulation and combined electric and acoustic stimulation (EAS). When acoustic information was added to electrically stimulated information performance increased by 17–23 percentage points on tests of word and sentence recognition in quiet and sentence recognition in noise. On average, the EAS patients achieved higher scores on CNC words than patients fit with a unilateral cochlear implant. While the best EAS patients did not outperform the best patients fit with a unilateral cochlear implant, proportionally more EAS patients achieved very high scores on tests of speech recognition than unilateral cochlear implant patients.

Speech Recognition Materials and Ceiling Effects: Considerations for Cochlear Implant Programs

Cochlear implant recipients have demonstrated remarkable increases in speech perception since US FDA approval was granted in 1984. Improved performance is due to a number of factors including improved cochlear implant technology, evolving speech coding strategies, and individuals with increasingly more residual hearing receiving implants. Despite this evolution, the same recommendations for pre- and postimplant speech recognition testing have been in place for over 10 years in the United States. To determine whether new recommendations are warranted, speech perception performance was assessed for 156 adult, postlingually deafened implant recipients as well as 50 hearing aid users on monosyllabic word recognition (CNC) and sentence recognition in quiet (HINT and AzBio sentences) and in noise (BKB-SIN). Results demonstrated that for HINT sentences in quiet, 28% of the subjects tested achieved maximum performance of 100% correct and that scores did not agree well with monosyllables (CNC) or sentence recognition in noise (BKB-SIN). For a more difficult sentence recognition material (AzBio), only 0.7% of the subjects achieved 100% performance and scores were in much better agreement with monosyllables and sentence recognition in noise. These results suggest that more difficult materials are needed to assess speech perception performance of postimplant patients – and perhaps also for determining implant candidacy.

Development and Validation of the AzBio Sentence Lists

Objectives: The goal of this study was to create and validate a new set of sentence lists that could be used to evaluate the speech perception abilities of hearing-impaired listeners and cochlear implant (CI) users. Our intention was to generate a large number of sentence lists with an equivalent level of difficulty for the evaluation of performance over time and across conditions. Design: The AzBio sentence corpus includes 1000 sentences recorded from two female and two male talkers. The mean intelligibility of each sentence was estimated by processing each sentence through a five-channel CI simulation and calculating the mean percent correct score achieved by 15 normal-hearing listeners. Sentences from each talker were sorted by percent correct score, and 165 sentences were selected from each talker and were then sequentially assigned to 33 lists, each containing 20 sentences (5 sentences from each talker). List equivalency was validated by presenting all lists, in random order, to 15 CI users. Results: Using sentence scores from the CI simulation study produced 33 lists of sentences with a mean score of 85% correct. The results of the validation study with CI users revealed no significant differences in percent correct scores for 29 of the 33 sentence lists. However, individual listeners demonstrated considerable variability in performance on the 29 lists. The binomial distribution model was used to account for the inherent variability observed in the lists. This model was also used to generate 95% confidence intervals for one and two list comparisons. A retrospective analysis of 172 instances where research subjects had been tested on two lists within a single condition revealed that 94% of results were accurately contained within these confidence intervals. Conclusions: The use of a five-channel CI simulation to estimate the intelligibility of individual sentences allowed for the creation of a large number of sentence lists with an equivalent level of difficulty. The results of the validation procedure with CI users found that 29 of 33 lists allowed scores that were not statistically different. However, individual listeners demonstrated considerable variability in performance across lists. This variability was accurately described by the binomial distribution model and was used to estimate the magnitude of change required to achieve statistical significance when comparing scores from one and two lists per condition. Fifteen sentence lists have been included in the AzBio Sentence Test for use in the clinical evaluation of hearing-impaired listeners and CI users. An additional eight sentence lists have been included in the Minimum Speech Test Battery to be distributed by the CI manufacturers for the evaluation of CI candidates.

Implications of minimizing trauma during conventional cochlear implantation.

Objective: To describe the relationship between implantation-associated trauma and postoperative speech perception scores among adult and pediatric patients undergoing cochlear implantation using conventional length electrodes and minimally traumatic surgical techniques. Study Design: Retrospective chart review (2002-2010). Setting: Tertiary academic referral center. Patients: All subjects with significant preoperative low-frequency hearing (≤70 dB HL at 250 Hz) who underwent cochlear implantation with a newer generation implant electrode (Nucleus Contour Advance, Advanced Bionics HR90K [1J and Helix], and Med El Sonata standard H array) were reviewed. Intervention(s): Preimplant and postimplant audiometric thresholds and speech recognition scores were recorded using the electronic medical record. Main Outcome Measure(s): Postimplantation pure tone threshold shifts were used as a surrogate measure for extent of intracochlear injury and correlated with postoperative speech perception scores. Results: Between 2002 and 2010, 703 cochlear implant (CI) operations were performed. Data from 126 implants were included in the analysis. The mean preoperative low-frequency pure-tone average was 55.4 dB HL. Hearing preservation was observed in 55% of patients. Patients with hearing preservation were found to have significantly higher postoperative speech perception performance in the CI-only condition than those who lost all residual hearing. Conclusion: Conservation of acoustic hearing after conventional length cochlear implantation is unpredictable but remains a realistic goal. The combination of improved technology and refined surgical technique may allow for conservation of some residual hearing in more than 50% of patients. Germane to the conventional length CI recipient with substantial hearing loss, minimizing trauma allows for improved speech perception in the electric condition. These findings support the use of minimally traumatic techniques in all CI recipients, even those destined for electric-only stimulation.

Impact of electrode design and surgical approach on scalar location and cochlear implant outcomes

Three surgical approaches: cochleostomy (C), round window (RW), and extended round window (ERW); and two electrodes types: lateral wall (LW) and perimodiolar (PM), account for the vast majority of cochlear implantations. The goal of this study was to analyze the relationship between surgical approach and electrode type with final intracochlear position of the electrode array and subsequent hearing outcomes.

Combining acoustic and electric stimulation in the service of speech recognition.

Abstract The majority of recently implanted, cochlear implant patients can potentially benefit from a hearing aid in the ear contralateral to the implant. When patients combine electric and acoustic stimulation, word recognition in quiet and sentence recognition in noise increase significantly. Several studies suggest that the acoustic information that leads to the increased level of performance resides mostly in the frequency region of the voice fundamental, e.g. 125 Hz for a male voice. Recent studies suggest that this information aids speech recognition in noise by improving the recognition of lexical boundaries or word onsets. In some noise environments, patients with bilateral implants can achieve similar levels of performance as patients who combine electric and acoustic stimulation. Patients who have undergone hearing preservation surgery, and who have electric stimulation from a cochlear implant and who have low-frequency hearing in both the implanted and not-implanted ears, achieve the best performance in a high noise environment. Sumario La mayoría de los usuarios recientes de implante coclear, pueden potencialmente beneficiarse de un auxiliar auditivo en el oído contralateral al implantado. Cuando los pacientes combinan la estimulación eléctrica y acústica, el reconocimiento de palabras en silencio y el reconocimiento de oraciones aumenta significativamente. Algunos estudios sugieren que la información acústica que permite el mayor nivel de rendimiento, reside sobre todo en la región frecuencial de la fundamental de la voz, p.ej., 125 Hz en la voz masculina. Estudios recientes sugieren que esta información ayuda para reconocer el lenguaje en ruido, mejorando el reconocimiento de las transiciones lexicales que ocurren en el inicio de las palabras. En algunos ambientes, los pacientes con implante bilateral pueden alcanzar niveles similares de rendimiento a los de quienes combinan la estimulación eléctrica con la acústica. Los pacientes que han sido sujetos de cirugía para preservar la audición, y que tienen estimulación eléctrica de un implante coclear y audición en las frecuencias graves tanto en el oído implantado como en el no implantado, alcanzan los mejores rendimientos en ambientes con ruido intenso.

Evidence for the Expansion of Adult Cochlear Implant Candidacy

Objectives: The primary objective of this study was to determine whether a revision and/or expansion of current audiologic cochlear implant candidacy criteria is warranted. Design: The study design was a retrospective review of postoperative speech perception performance for 22 adult cochlear implant recipients who demonstrated preoperative Consonant Nucleus Consonant word recognition scores of 30% or higher in the best-aided condition. This criterion was chosen to exceed that specified by the North American clinical trial of the Nucleus Freedom cochlear implant system. Results: The mean preoperative best-aided monosyllabic word score for the 22 patients was 41% correct. The degree of postoperative benefit for the best postoperative condition (electric only or bimodal) ranged from 10 to 68 percentage points with a mean benefit of 27 percentage points for the electric-only condition and 40 percentage points for the bimodal condition. Statistical analyses revealed highly significant differences between preoperative-aided, implant-only, and bimodal performance on Consonant Nucleus Consonant monosyllabic word recognition performance. That is, both postoperative scores—electric only and bimodal—were significantly different from one another and from the preoperative best-aided performance. Conclusions: The current results suggest that a large-scale reassessment of manufacturer and Medicare preoperative audiologic candidacy criteria for adults is warranted to allow more hearing-impaired individuals to take advantage of the benefits offered by cochlear implantation.

Cochlear implantation with hearing preservation yields significant benefit for speech recognition in complex listening environments

Objective: The aim of this study was to assess the benefit of having preserved acoustic hearing in the implanted ear for speech recognition in complex listening environments. Design: The present study included a within-subjects, repeated-measures design including 21 English-speaking and 17 Polish-speaking cochlear implant (CI) recipients with preserved acoustic hearing in the implanted ear. The patients were implanted with electrodes that varied in insertion depth from 10 to 31 mm. Mean preoperative low-frequency thresholds (average of 125, 250, and 500 Hz) in the implanted ear were 39.3 and 23.4 dB HL for the English- and Polish-speaking participants, respectively. In one condition, speech perception was assessed in an eight-loudspeaker environment in which the speech signals were presented from one loudspeaker and restaurant noise was presented from all loudspeakers. In another condition, the signals were presented in a simulation of a reverberant environment with a reverberation time of 0.6 sec. The response measures included speech reception thresholds (SRTs) and percent correct sentence understanding for two test conditions: CI plus low-frequency hearing in the contralateral ear (bimodal condition) and CI plus low-frequency hearing in both ears (best-aided condition). A subset of six English-speaking listeners were also assessed on measures of interaural time difference thresholds for a 250-Hz signal. Results: Small, but significant, improvements in performance (1.7–2.1 dB and 6–10 percentage points) were found for the best-aided condition versus the bimodal condition. Postoperative thresholds in the implanted ear were correlated with the degree of electric and acoustic stimulation (EAS) benefit for speech recognition in diffuse noise. There was no reliable relationship among measures of audiometric threshold in the implanted ear nor elevation in threshold after surgery and improvement in speech understanding in reverberation. There was a significant correlation between interaural time difference threshold at 250 Hz and EAS-related benefit for the adaptive speech reception threshold. Conclusions: The findings of this study suggest that (1) preserved low-frequency hearing improves speech understanding for CI recipients, (2) testing in complex listening environments, in which binaural timing cues differ for signal and noise, may best demonstrate the value of having two ears with low-frequency acoustic hearing, and (3) preservation of binaural timing cues, although poorer than observed for individuals with normal hearing, is possible after unilateral cochlear implantation with hearing preservation and is associated with EAS benefit. The results of this study demonstrate significant communicative benefit for hearing preservation in the implanted ear and provide support for the expansion of CI criteria to include individuals with low-frequency thresholds in even the normal to near-normal range.

Cochlear Implantation in Children with Auditory Neuropathy Spectrum Disorder: Long-Term Outcomes

BACKGROUND Best practices concerning the audiological management of the child diagnosed with auditory neuropathy spectrum disorder (ANSD) have not been definitively defined nor fully understood. One reason is that previous studies have demonstrated conflicting findings regarding the outcomes of cochlear implantation for children with ANSD. Thus, the question remains whether children with ANSD are able to achieve similar outcomes following cochlear implantation as those children with sensorineural hearing loss (SNHL). PURPOSE To assess speech perception outcomes for children with cochlear implants who have a diagnosis of ANSD as well as their age-matched peers who have sensorineural hearing loss. RESEARCH DESIGN Retrospective study STUDY SAMPLE Thirty-five subject pairs (n = 70) ranging in age at implant activation from to 10 to 121 mo (mean 39.2 mo) were included in this retrospective study. Subjects were matched on variables including age at initial implant activation and months of implant use at postoperative test point. DATA COLLECTION AND ANALYSIS Speech recognition scores for monosyllabic and multisyllabic stimuli were compared across the subject groups. For those not developmentally and/or linguistically ready for completion of open-set speech recognition testing with recorded stimuli, GASP (Glendonald Auditory Screening Procedure) word recognition and/or questionnaire data using either the LittlEARS or Meaningful Auditory Integration Scale were compared across the groups. Statistical analysis using a repeated-measures analysis of variance (ANOVA) evaluated the effects of etiology (ANSD or SNHL) on postoperative outcomes. RESULTS The results of this study demonstrate that children with ANSD can clearly benefit from cochlear implantation and that their long-term outcomes are similar to matched peers with SNHL on measures of speech recognition. There were no significant differences across the ANSD and SNHL groups on any of the tested measures. CONCLUSION Cochlear implantation is a viable treatment option for children with a diagnosis of ANSD who are not making auditory progress with hearing aids that have been fit using the Desired Sensation Level method (DSL v5.0). Expected outcomes of cochlear implantation for children with ANSD, excluding children with cochlear nerve deficiency, are no different than for children with non-ANSD SNHL. These results are important for counseling families on the expected outcomes and realistic expectations following cochlear implantation for children with ANSD who demonstrate no evidence of cochlear nerve deficiency.

Cochlear implantation in the octogenarian and nonagenarian.

Objective: Previous studies have shown that cochlear implant outcomes with respect to surgical morbidity and speech perception may be poorer in elderly patients as compared with younger adults. However, recent anecdotal reports suggest that elderly cochlear implant recipients are achieving increasingly higher speech perception performance and fewer surgical complications than previously noted. Our objective is to review cochlear implant outcomes using newer generation implants and minimally traumatic cochleostomy techniques in patients 80 years and older compared with younger adult recipients. Study Design: Retrospective chart review. Setting: Tertiary referral center. Patients: All adult cochlear implant recipients (232 patients, 258 implants) who underwent implantation with a Nucleus Freedom, Advanced Bionics HR90k, or Med El Sonata device at a tertiary academic institution. Intervention(s): Postoperative speech perception scores and clinical data extraction using the electronic medical record. Main Outcome Measure(s): Anesthetic and surgical complications, device malfunction, operative time, admission status, length of hospital stay, and postoperative speech perception scores were collected after 50 cochlear implant procedures in patients who were implanted beyond the eighth decade and 208 among younger adults (18-79 yr). Results: Patients 80 years or older were more likely to have anesthetic complications and require hospital admission (p < 0.05). There was no statistical difference between groups with respect to surgical complications or device malfunction. Speech perception analysis revealed similar outcomes for older and younger patients. Conclusion: Cochlear implantation is well tolerated across all adult age groups with a relatively low risk for adverse surgical events or device malfunction. Given the favorable safety profile and high levels of speech perception achieved by older patients, routine implantation of octogenarian and nonagenarians seems warranted. These results also stress the need for thorough preoperative evaluation of elderly patients, given the increased likelihood for perioperative anesthetic complications.