Cochlear implantation on prelingually deafened adults

The Chronological Evolution of Cochlear Implant Contraindications: A Comprehensive Review

Cochlear implantation has emerged as a transformative intervention in addressing profound hearing loss, offering a paradigm shift in auditory rehabilitation for individuals with restricted auditory function. Throughout its history, the understanding of contraindications for cochlear implant (CI) surgery has evolved significantly. This review comprehensively analyzes the chronological advancements in the understanding of CI contraindications, examining studies conducted from historical timelines to the present. Recent research has revealed significant developments in the field, prompting a reevaluation of established criteria and resulting in expanded indications for CI. The chronological evolution of contraindications underscores the transformative nature of the field, offering potential improvements in outcomes and enhancing the quality of life for individuals with profound hearing loss. In conclusion, this narrative review emphasizes the dynamic nature of the field, where the reevaluation of contraindications has created new opportunities and broader indications for CI. The emerging prospects, including improved outcomes and enhanced quality of life, hold promise for individuals with profound hearing loss.

Long-term speech perception performance in prelingually deafened adult cochlear implant recipients

To investigate the postoperative long-term outcomes after an average of 9.2 years following cochlear implantation (CI) in prelingually deafened adults, along with preimplantation factors predicting postoperative outcomes.

Twenty-six prelingually deafened adults who underwent CI at >18 years were compared with those who had undergone CI in childhood (<9 years) and were >10 years old. Outcome measures includedhearing thresholds, preoperative and postoperative aided hearing level (HL), speech discrimination score (SDS), and Categories of Auditory Performance (CAP) scores. Correlation analyses were performed on the following: SDS results, aided HL, school attendant status, implant manufacturers, and speech processor models.

Improvement was achieved in the aided HL and SDS results, although these results were not better than those of the child group. CAP score was also statistically significantly improved after CI. Statistically significant correlation between the preoperative SDS and postoperative HL with CI results was observed. In other words, the better the preoperative SDS results, the better the postoperative SDS results.

Prelingually deafened adults achieved considerable improvement through CI. It is important to understand that patients achieving better hearing with a well-fitted hearing aid and good SDS performance before surgery may be good candidates for CI.

Cochlear implant in prelingually hearing-impaired adults: prognostic factors and results

Objectives

The aim of present study is to evaluate the impact of prognostic factors on the outcome in a group of prelingually hearing-impaired patients submitted to cochlear implantation (CI) at an adult age.

Methods

This is a retrospective study on a cohort of prelingually severe-to-profound hearing-impaired patients cochlear implanted in adulthood and followed by a single audiology centre. We correlated post-CI results in term of speech perception with patients’ speech perception with hearing aids before implantation, history of progression of hearing loss (HL), and levels of education and cognition. The study group was composed of 49 patients.

Results

Post-CI open-set recognition score in silence and noise was significantly correlated with pre-CI open-set recognition score in silence and with background noise. Patients with a history of progression of HL gained significantly better results. Furthermore, we found higher improvements in patients with a higher level of education.

Conclusions

Prelingually deafened patients implanted in adulthood achieved satisfactory results. Significantly better results were achieved by patients with better pre-operative speech perception scores, progressive HL and higher level of education.

Intelligibility of the Patient's Speech Predicts the Likelihood of Cochlear Implant Success in Prelingually Deaf Adults

OBJECTIVES

The objective of this study was to determine the validity and clinical applicability of intelligibility of the patient's own speech, measured via a Vowel Identification Test (VOW), as a predictor of speech perception for prelingually deafened adults after 1 year of cochlear implant use. Specifically, the objective was to investigate the probability that a prelingually deaf patient, given a VOW score above (or below) a chosen cutoff point, reaches a postimplant speech perception score above (or below) a critical value. High predictive values for VOW could support preimplant counseling and implant candidacy decisions in individual patients.

DESIGN

One hundred and fifty-two adult cochlear implant candidates with prelingual hearing impairment or deafness took part as speakers in a VOW; 149 speakers completed the test successfully. Recordings of the speech stimuli, consisting of nonsense words of the form [h]-V-[t], where V represents one of 15 vowels/diphthongs ([(Equation is included in full-text article.)]), were presented to two normal-hearing listeners. VOW score was expressed as the percentage of vowels identified correctly (averaged over the 2 listeners). Subsequently, the 149 participants enrolled in the cochlear implant selection procedure. Extremely poor speakers were excluded from implantation, as well as patients who did not meet regular selection criteria as developed for postlingually deafened patients. From the 149 participants, 92 were selected for implantation. For the implanted group, speech perception data were collected at 1-year postimplantation.

RESULTS

Speech perception score at 1-year postimplantation (available for 77 of the 92 implanted participants) correlated positively with preimplant intelligibility of the patient's speech, as represented by VOW (r = 0.79, p < 0.00001): the more intelligible the patient's speech, the higher the predicted postimplant speech perception score. This correlation is explained by the hypothesis that the two variables have a common driving force, i.e., (in)adequacy of auditory speech input in the earliest years of life. With a 60% cutoff point, VOW can discriminate between individuals with "above-chance" postimplant speech perception and those with "chance level" postimplant speech perception with sensitivity and specificity of 0.84 and 0.86, respectively. The probability that a patient with a VOW score ≥ 60% achieves "above-chance" speech perception after implantation is 0.91. Conversely, the probability that a patient with VOW < 60% reaches "above-chance" speech perception is 0.25.

CONCLUSIONS

For prelingually deaf adults, intelligibility of the patient's speech-as represented by VOW-is a valid predictor of postimplant speech perception. A patient with a VOW score above a preset cutoff is much more likely to develop acceptable speech perception after implantation than a patient with a VOW score below that cutoff. The binary classification based on VOW and the associated probabilities of cochlear implant success in terms of speech perception can be used-in addition to existing criteria-to support the clinician in guiding patient expectations and in considering implant candidacy for individual patients.

An Eye Tracking Study on the Perception and Comprehension of Unimodal and Bimodal Linguistic Inputs by Deaf Adolescents

An eye tracking experiment explored the gaze behavior of deaf individuals when perceiving language in spoken and sign language only, and in sign-supported speech (SSS). Participants were deaf (n = 25) and hearing (n = 25) Spanish adolescents. Deaf students were prelingually profoundly deaf individuals with cochlear implants (CIs) used by age 5 or earlier, or prelingually profoundly deaf native signers with deaf parents. The effectiveness of SSS has rarely been tested within the same group of children for discourse-level comprehension. Here, video-recorded texts, including spatial descriptions, were alternately transmitted in spoken language, sign language and SSS. The capacity of these communicative systems to equalize comprehension in deaf participants with that of spoken language in hearing participants was tested. Within-group analyses of deaf participants tested if the bimodal linguistic input of SSS favored discourse comprehension compared to unimodal languages. Deaf participants with CIs achieved equal comprehension to hearing controls in all communicative systems while deaf native signers with no CIs achieved equal comprehension to hearing participants if tested in their native sign language. Comprehension of SSS was not increased compared to spoken language, even when spatial information was communicated. Eye movements of deaf and hearing participants were tracked and data of dwell times spent looking at the face or body area of the sign model were analyzed. Within-group analyses focused on differences between native and non-native signers. Dwell times of hearing participants were equally distributed across upper and lower areas of the face while deaf participants mainly looked at the mouth area; this could enable information to be obtained from mouthings in sign language and from lip-reading in SSS and spoken language. Few fixations were directed toward the signs, although these were more frequent when spatial language was transmitted. Both native and non-native signers looked mainly at the face when perceiving sign language, although non-native signers looked significantly more at the body than native signers. This distribution of gaze fixations suggested that deaf individuals – particularly native signers – mainly perceived signs through peripheral vision.

The effects of early auditory-based intervention on adult bilateral cochlear implant outcomes

OBJECTIVES

The goal of this exploratory study was to determine the types of improvement that sequentially implanted auditory-verbal and auditory-oral adults with prelingual and childhood hearing loss received in bilateral listening conditions, compared to their best unilateral listening condition.

METHODS

Five auditory-verbal adults and five auditory-oral adults were recruited for this study. Participants were seated in the center of a 6-loudspeaker array. BKB-SIN sentences were presented from 0° azimuth, while multi-talker babble was presented from various loudspeakers. BKB-SIN scores in bilateral and the best unilateral listening conditions were compared to determine the amount of improvement gained.

RESULTS

As a group, the participants had improved speech understanding scores in the bilateral listening condition. Although not statistically significant, the auditory-verbal group tended to have greater speech understanding with greater levels of competing background noise, compared to the auditory-oral participants.

DISCUSSION

Bilateral cochlear implantation provides individuals with prelingual and childhood hearing loss with improved speech understanding in noise. A higher emphasis on auditory development during the critical language development years may add to increased speech understanding in adulthood. However, other demographic factors such as age or device characteristics must also be considered.

CONCLUSION

Although both auditory-verbal and auditory-oral approaches emphasize spoken language development, they emphasize auditory development to different degrees. This may affect cochlear implant (CI) outcomes. Further consideration should be made in future auditory research to determine whether these differences contribute to performance outcomes. Additional investigation with a larger participant pool, controlled for effects of age and CI devices and processing strategies, would be necessary to determine whether language learning approaches are associated with different levels of speech understanding performance.

Receptive language as a predictor of cochlear implant outcome for prelingually deaf adults

OBJECTIVE

This study investigated outcomes and predictive factors, specifically language skills, for a group of prelingually hearing-impaired adults who received a cochlear implant.

DESIGN

Speech perception data, demographic information, and other related variables such as communication mode, residual hearing, and receptive language abilities were explored. Pre- and post-implant speech perception scores were compared and multiple regression analysis was used to identify significant predictive relationships.

STUDY SAMPLE

The study included 43 adults with a prelingual onset of hearing loss, who proceeded with cochlear implantation at the Royal Victorian Eye and Ear Hospital in Melbourne, Australia.

RESULTS

The majority of patients experienced benefit from their cochlear implants, with 88% demonstrating significant improvement in speech perception performance. Volunteers achieved better post-operative speech perception scores if they had a shorter duration of severe-to-profound hearing loss, better language skills, and used an exclusively oral communication mode.

CONCLUSIONS

Although post-operative speech perception performance is significantly poorer for prelingually hearing-impaired adults compared to postlingually hearing-impaired patients, the study group demonstrated significant benefit from their cochlear implants. The variability in post-operative outcomes can be predicted to some extent from the hearing history and language abilities of the individual patient.

Delayed prelingual cochlear implantation in childhood and puberty

OBJECTIVE

To evaluate the results of delayed cochlear impantion performed in childhood and puberty in the light of speech language pathology assessments.

METHODS

Totally 49 children with prelingual profound hearing loss were included in the study. All children received a cochlear implant between the ages of 5 and 19 years (Group 1 aged between 5 and 9 years, group 2 aged between 10 and 14 years, group 3 aged between and 15 and 19 years). The MAIS, MUSS and PLS-4 scores of children were evaluated one month before, and one year and two years after the operation. The descriptive statistics included several independent variables; age of implantation; gender; trade name of the implant; preoperative duration of hearing aid use; preoperative special education, family support and additional handicap. These variables were categorical variables. We used repeated measures analysis of variance to test improvements in MAIS, MUSS and PLS scores, and whether this improvement depend on the independent variables. In addition, we also tested the interaction between time and the independent variables.

RESULTS

The preoperative MAIS, MUSS and language scores were significantly higher in older children compared to younger children (p<0.01). After two years these scores were similar between the all age groups (p>0.4). There was a significant age and time interaction (p=0.005). That is, improvement continued in all age groups in a parallel way and group 2 reached to the level of group 1 after two years. However, group 3 almost reached to a plateau level after two years. The family support was associated with the MAIS, MUSS and language scores of the patients (p=0.01), and there was a family support-time interaction (p<0.0001). In group 1 and 2, the way of communication shifted from total communication (lip reading, sign language, auditory) to auditory-verbal communication in a significant number of the patients (p<0.01). However, that change in the way of communication was not statistically significant in group 3 (p>0.05).

CONCLUSION

The decision of delayed cochlear implantation in children can be made in the light of following parameters. A good family support is most important. The patients must be wearing hearing aids regularly since early childhood, and preferably use the auditory verbal communication. Evaluation of the patient with MAIS, MUSS and PLS is important to understand the level of receptive and expressive communication level.

Cochlear implantation (CI) for prelingual deafness: the relevance of studies of brain organization and the role of first language acquisition in considering outcome success

Cochlear implantation (CI) for profound congenital hearing impairment, while often successful in restoring hearing to the deaf child, does not always result in effective speech processing. Exposure to non-auditory signals during the pre-implantation period is widely held to be responsible for such failures. Here, we question the inference that such exposure irreparably distorts the function of auditory cortex, negatively impacting the efficacy of CI. Animal studies suggest that in congenital early deafness there is a disconnection between (disordered) activation in primary auditory cortex (A1) and activation in secondary auditory cortex (A2). In humans, one factor contributing to this functional decoupling is assumed to be abnormal activation of A1 by visual projections-including exposure to sign language. In this paper we show that that this abnormal activation of A1 does not routinely occur, while A2 functions effectively supramodally and multimodally to deliver spoken language irrespective of hearing status. What, then, is responsible for poor outcomes for some individuals with CI and for apparent abnormalities in cortical organization in these people? Since infancy is a critical period for the acquisition of language, deaf children born to hearing parents are at risk of developing inefficient neural structures to support skilled language processing. A sign language, acquired by a deaf child as a first language in a signing environment, is cortically organized like a heard spoken language in terms of specialization of the dominant perisylvian system. However, very few deaf children are exposed to sign language in early infancy. Moreover, no studies to date have examined sign language proficiency in relation to cortical organization in individuals with CI. Given the paucity of such relevant findings, we suggest that the best guarantee of good language outcome after CI is the establishment of a secure first language pre-implant-however that may be achieved, and whatever the success of auditory restoration.

Revisiting the adaptive and maladaptive effects of crossmodal plasticity

One of the most striking demonstrations of experience-dependent plasticity comes from studies of sensory-deprived individuals (e.g., blind or deaf), showing that brain regions deprived of their natural inputs change their sensory tuning to support the processing of inputs coming from the spared senses. These mechanisms of crossmodal plasticity have been traditionally conceptualized as having a double-edged sword effect on behavior. On one side, crossmodal plasticity is conceived as adaptive for the development of enhanced behavioral skills in the remaining senses of early-deaf or blind individuals. On the other side, crossmodal plasticity raises crucial challenges for sensory restoration and is typically conceived as maladaptive since its presence may prevent optimal recovery in sensory-re-afferented individuals. In the present review we stress that this dichotomic vision is oversimplified and we emphasize that the notions of the unavoidable adaptive/maladaptive effects of crossmodal reorganization for sensory compensation/restoration may actually be misleading. For this purpose we critically review the findings from the blind and deaf literatures, highlighting the complementary nature of these two fields of research. The integrated framework we propose here has the potential to impact on the way rehabilitation programs for sensory recovery are carried out, with the promising prospect of eventually improving their final outcomes.

Cochlear implants in children deafened by congenital cytomegalovirus and matched Connexin 26 peers

OBJECTIVE

To compare the long-term speech perception and production outcomes after cochlear implantation (CI) in children deafened by congenital cytomegalovirus (cCMV) with a matched group of Cx26-CI children by controlling for chronological age and magnetic resonance imaging (MRI) findings.

METHODS

Retrospective review of 12 cCMV-CI children and matched Cx26-CI children for speech perception and speech production outcomes.

RESULTS

Two trends were seen in our data. First, cCMV-CI children with normal MRI scans perform equally or even slightly better on speech perception tests compared to their Cx26-CI peers during the first three years. The majority of cCMV-CI children with normal MRI scans (5 out of 7), suffered from a delayed-onset SNHL. Their mean age at first implantation (2y9m, range 15-82m) was higher compared to their matched Cx26 peers (9m, range 7-12m). Before being implanted, the majority of these delayed-onset hearing impaired children had benefited from a certain period of normal hearing (with or without amplification of a hearing aid). Possibly, this input might have led to an advantage the first three years after CI. Second, results between cCMV-CI children with and cCMV-CI children without MRI abnormalities and their matched Cx26-CI counterparts tentatively suggest that, over a 5-yr follow-up period, cCMV-CI children with abnormalities on MRI scans catch up for speech perception, but lag behind for speech production.

CONCLUSION

cCMV-CI children with normal MRI scans perform equally or even slightly better on speech perception tests compared to their Cx26-CI peers during the first three years, whereas results between cCMV-CI children with and cCMV-CI children without MRI abnormalities and their matched Cx26-CI counterparts tentatively suggest that, over a 5-yr follow-up period, cCMV-CI children with abnormal MRI scans catch up for speech perception, but lag behind for speech production. In future, the inclusion of MRI results may assist in improved counseling of parents with cCMV deafened children seeking CI.

How does visual language affect crossmodal plasticity and cochlear implant success?

Cochlear implants (CI) are the most successful intervention for ameliorating hearing loss in severely or profoundly deaf children. Despite this, educational performance in children with CI continues to lag behind their hearing peers. From animal models and human neuroimaging studies it has been proposed the integrative functions of auditory cortex are compromised by crossmodal plasticity. This has been argued to result partly from the use of a visual language. Here we argue that 'cochlear implant sensitive periods' comprise both auditory and language sensitive periods, and thus cannot be fully described with animal models. Despite prevailing assumptions, there is no evidence to link the use of a visual language to poorer CI outcome. Crossmodal reorganisation of auditory cortex occurs regardless of compensatory strategies, such as sign language, used by the deaf person. In contrast, language deprivation during early sensitive periods has been repeatedly linked to poor language outcomes. Language sensitive periods have largely been ignored when considering variation in CI outcome, leading to ill-founded recommendations concerning visual language in CI habilitation.

Speech intelligibility as a predictor of cochlear implant outcome in prelingually deafened adults

OBJECTIVES

Among adult patients with prelingual deafness, interindividual variability in speech perception outcome after cochlear implantation is generally large. It was hypothesized that the intelligibility of the patient's own speech may be predictive of speech perception with a cochlear implant. The objectives were (1) to provide a validation of a new test battery as a measurement tool for intelligibility using a group of prelingually deafened patients; (2) to investigate the validity of the test battery as a predictor of postimplant speech perception, based on preliminary data with a cochlear implant from a subgroup of patients; and (3) to investigate the validity of the test battery as a predictor of postimplant health-related quality of life (HRQoL) for the same subgroup of patients.

DESIGN

Twenty-five adult cochlear implant candidates with prelingual deafness participated in this study. Average age at onset of deafness was 8 mos (range 0 to 4 yrs). Speech samples from the participants were recorded and presented to two normal-hearing listeners. Results from the seven intelligibility tests in the battery were subjected to analyses of reliability and validity. Furthermore, the multiple test outcomes were submitted to a Principal Component Analysis to investigate the possibility of summarizing the data. Subsequently, from the group of 25 participants, 9 participants with above-average intelligibility were selected for implantation. Speech perception data with a cochlear implant from the nine implantees were collected at 12 mos postimplantation, as well as HRQoL data. Predictive validity of the intelligibility test battery was determined, using the postimplant data as the criterion.

RESULTS

Results from the 25 participants averaged over listeners showed that all tests in the battery had good reliability and validity as measures of intelligibility. Principal Component Analysis showed that the multiple test outcomes could be summarized by a single underlying variable. Despite the early age at onset of deafness, the subgroup of nine participants who received a cochlear implant included several good performers in terms of speech perception with the implant. The intelligibility test battery summary score had good validity as a predictor of postimplant outcome: the more intelligible the participant's speech, the better his or her speech perception outcome with the cochlear implant. Availability of effective auditory input in early life may be the fundamental factor underlying the potential for speech perception with a cochlear implant in later life. The intelligibility test battery can be reduced to a single test to minimize testing time without negatively affecting its predictive validity. Predictive validity of the intelligibility test battery can be generalized to HRQoL outcomes of cochlear implantation, provided these outcomes are concerned with speech processing abilities.

CONCLUSIONS

The new test battery (or its reduced version), used as a measure of intelligibility, is a promising tool for guiding cochlear implant candidacy decisions and counseling for individual patients with prelingual deafness. Because intelligibility has superior predictive power in comparison to age at onset of deafness, the latter should be discarded as an exclusion criterion for cochlear implantation.

Cochlear implants: current status and future potential

This article reviews the current status of cochlear implantation in both adults and children, including expanding candidacy groups, bilateral implantation, advances in speech processing software, internal and external device hardware, surgical techniques and outcomes. Promising advances, novel therapies and evolving concepts are also highlighted in terms of their future impact on clinical outcomes.

Observation of cortical activity during speech stimulation in prelingually deafened adults with cochlear implantation by positron emission tomography-computed tomography

OBJECTIVES

We evaluated the cortical activity of 2 successful prelingually deafened adult cochlear implant (CI) users who have been trained by auditory-verbal/oral communication since childhood.

METHODS

Changes in regional cerebral blood flow were measured by positron emission tomography using '8F-fluorodeoxyglucose while the subjects were receiving auditory language stimuli by listening to a story. Ten normal-hearing volunteers were observed as age-matched control subjects.

RESULTS

In both cases, the auditory-related regions, when compared to same regions in the control subjects, showed hypermetabolism in the left dorsolateral prefrontal cortex and the left precentral gyrus--similar to that in successful CI users who are prelingually deafened children or postlingually deafened adults. Both subjects had the ability to activate these areas, and this ability might be one of the reasons that accounts for such exceptionally good performance in older prelingually deaf CI users. As for the visual-related regions, hypometabolism was observed in Brodmann areas 18 and 19, and this finding might be related to the intensive auditory-verbal/oral education that the subjects had received since childhood.

CONCLUSIONS

Despite the limits imposed by the small sample size and the spatial resolution of positron emission tomography, this study yielded insights into the nature of the brain plasticity in prelingually deafened adults who are successful CI users.

Cochlear implantation in patients with prelingual hearing loss

CONCLUSION

The average age at the time of cochlear implantation is progressively being reduced. While cochlear obstruction and perilymph/cerebello-spinal fluid gusher were found in some cases, preoperative MRI and CT scans were predictive of such occurrences. The preoperative developmental quotient in the Cognitive-Adaptive Area was strongly correlated to the postoperative development in the Language-Social Area.

OBJECTIVE

To summarize the background, implant devices, intraoperative findings, and postoperative developmental quotients of prelingually deafened patients who underwent cochlear implantation.

METHODS

We conducted a retrospective chart review of 134 prelingually deafened cochlear implant recipients.

RESULTS

The median age at implantation was 3 years and 5 months. Most patients were born deaf without any known etiologies. In most cases, the transmastoid facial recess approach was utilized. Cochlear obstruction was identified in four patients, all of whom lost their hearing as a result of meningitis. Perilymph/cerebello-spinal fluid gusher was observed in six patients with inner ear anomalies. The preoperative developmental quotient for the Cognitive-Adaptive Area showed significant correlation with the postoperative developmental quotient in the Language-Social Area with a correlation coefficient of 0.71.

Cochlear implantation in adolescents with prelinguistic deafness

Objective: The aims of this study were to examine auditory function in a group of adolescents with prelingual deafness who received cochlear implants (CI) and to identify poor-outcome predictors in order to define reliable prognostic indicators useful in selecting patients for CI.

Study Design: Prospective study.

Setting: The study was conducted in the Audiology Unit of Cà Granda Ospedale Maggiore Policlinico, Milan, Italy.

Subjects and Methods: The study involved 45 adolescents (mean age at implantation: 13.4 ± 2.6 years, range: 11-18) with profound congenital hearing impairment with a follow-up of three years. Preimplantation and postimplantation auditory performance and speech perception were evaluated using the mean score of three hearing and speech perception tests (vowel-consonant-vowel [VCV], identification of disyllabic words, and recognition of short sentences) performed in auditory-only listening conditions.

Results: Significant improvements in all speech perception tests were observed after CI. However, 15 cases were considered “poor performers” (i.e., the auditory performance of these patients was less than 30 percent). The diagnosis of deafness in these subjects was significantly delayed (18.07 ± 6.25 and 34.4 ± 10.26 months in good and poor performers, respectively, P = 0.006), and their hearing threshold was significantly lower than in the good users group. The mean age at CI was 12.8 ± 2.33 and 14.53 ± 2.70 years in good and poor performers, respectively ( P = ns).

Conclusion: CI was shown to be a useful device with the ability to reverse the adverse consequences of hearing loss, particularly for prelingual adolescents who receive implantation early in life and who present a hearing threshold of 100 dB or better both at diagnosis and at surgery.