Abstract
The primary goal of the study was to assess the progress achieved across different implant age groups (0–2 years, 2.1–4 years and 4.1–6 years) using a comprehensive test battery approach targeting areas such as Audition, Speech Perception, Speech Intelligibility and Speech-Language.This cross-sectional study evaluated the outcomes of 40 children who underwent cochlear implantation at Sri Ramachandra Medical Centre, Chennai. A battery of tests included aided audiogram, Categorical Auditory Performance, Meaningful Auditory Integration Scale; Picture speech identification test in Tamil; Speech Intelligibility Rating Scale and Communication Developmental Eclectic Approach to Language Learning (COMDEALL) were administered to evaluate their auditory, speech perception, speech intelligibility and speech and language skills, respectively. The results of the study suggested that children implanted between 0 and 2 years of age demonstrated better performance in all tasks including audition, speech perception and intelligibility as well as speech and language when compared to the other two older groups. Children implanted between 0 and 2 years reached target milestones early in life similar to their hearing peers. However, children between (2.1– 4 years) also performed well and results indicated that they could catch up with intensive training. The present study reestablished the findings that early implantation (0–2 years) facilitates optimal progress when compared to implantation at later ages within the age range of 0–6 years. It also facilitates parent counseling regarding the realistic expectations with reference to different ages of implantation
Keywords: Cochlear implantation, Speech perception, Age at implantation, Speech, Language
Introduction
Cochlear implants (CI) have become a preferred choice of management for people with bilateral severe to profound hearing loss who do not benefit from conventional amplification systems. The success of a cochlear implant program depends on its ability to fulfil parental expectations and demonstrate optimal treatment outcomes. Variables that affect outcomes in CI include the deafness duration, the cause of hearing loss, age of deafness onset, amplification history prior to implant, mode of communication, the age of implantation, speech processor and the implant usage. However, other factors also affect the overall outcome include the transparency of a given program, team expertise, patient and parent motivation and rehabilitation facilities [1].
The National Institute of Health and Care Excellence (NICE), United Kingdom, reported that there are deficiencies in the cochlear implant program. It included the difficulties to compare non-homogeneity in the measure and protocols, lack of long term observational periods, absence of any observable benefits in daily circumstances and overall quality of life for the implanted person [2]. NICE reported that more large-scale studies were required to prospectively follow up patients on a periodic basis with standard outcome measures.
Though the Cochlear Implant Group of India (CIGI) has offered a set of guidelines for cochlear implant practice. However, a uniform protocol is not being followed throughout the country. Documentation of outcomes becomes even more challenging when the availability of standard language specific tests is limited. The published data that is available indicate that third-degree measurements like parent observations and questionnaires are usually used to report outcomes [1, 3, 4]. Hence, the present study will be the first attempt to implement and adapt a valuation protocol to assess outcome measures that include both direct and indirect measures. Given the plethora of tests available to evaluate outcome measures, a test battery has been systematically chosen to asses outcomes. In order to assess audition, a baseline aided audiometry was carried out, followed by Categorical Auditory Performance (CAP) Scale [5] and Meaningful Auditory Integration Skills (MAIS) questionnaires [6] was used. These tests are standard tools used by CI habilitationist across the world to measure auditory outcomes. The materials are universal and language free and are widely used test tools among the CI population. A direct measure of speech perception is more reliable as it reflects the perceptual abilities of the CI recipient. Picture speech identification test in Tamil [7] was used, as it is available in native Tamil language and can be easily administered on children with hearing impairement. Speech Intelligibility Rating (SIR) Scale was administered to assess speech intelligibility skills, as it is the standard tool to evaluate the same [5]. The Communication Developmental Eclectic Approach to Language Learning (COMDEALL) test tool [8] was also used to evaluate Speech and Language skills, as it is an Indian test material exclusively developed for the Indian population. In addition to speech and language the test also consists of domains that can be used to rule out behaviour and cognitive issues. Based on the chronological age and presence of language skills, an approximate age range of receptive and expressive language age can be obtained.
It is important to trace the trajectory of the children using the test battery targeting various areas of speech, language, and audition across different age groups. It is an established fact that early implantation before 24 months of age have better outcomes in terms of spoken language. However, children with CI show a large variability in performance and the question remains if the children implanted later will be able to catch-up or be consistent in language development with the NH counterparts as the implant age increases. Therefore, the primary aim of the study is to evaluate outcomes of children who have received CI at different age groups (Group I: 0–2 years, Group II: 2.1-4 years and Group III: 4.1–6 years). The objectives were to explore if (a) audition contributes to the development of age-appropriate language skills. (b) to compare the outcome measures across age groups (c) to compare the outcomes based on the duration of implant use.
Material and Methods
This study was approved by the Institutional Ethics Committee, Sri Ramachandra Institute of Higher Education and Research (DU).
Participants
The study design was a cross-sectional design that included 40 participants with unilateral CI who underwent surgery and completed one year of habilitation at Sri Ramachandra Medical centre. The procedure of the study was explained, and a written informed consent was obtained from the participants/guardian of the child prior to the study. Based on their age of implant (11 months–6 years); average age of implant- 3.3 years, the children (N: 40; 22 boys and 18 girls) were categorized into three different groups (Group I: 0–2 years, Group II: 2.1–4 years and Group III: 4.1–6 years) and recruited for the study. Children with history of amplification use and additional needs were excluded from the study. All the children used implants of three different companies with their prescribed speech processing strategies Fig.1
Fig. 1.
Mean aided PTA scores among the three age groups
A battery of tests was compiled to target the progress in areas of Audition, speech perception, speech intelligibility and speech and language post implantation. The tests included aided audiogram, Categorical Auditory Performance, Meaningful Auditory Integration Scale, Picture speech identification test in Tamil, Speech Intelligibility Rating Scale and Communication Developmental Eclectic Approach to Language Learning (COMDEALL).
The aided audiometry procedure involved testing the child across different frequency regions in a free field condition through loudspeakers routed to a dual channel calibrated audiometer (Piano Plus Inventis audiometer). The testing was carried out in an audiometric soundproof room with the ambient noise level in the sound within the permissible limits prescribed by ANSI-53, 1–1999 and the child was seated facing the examiner. Every child was tested individually, and the task was to respond to the stimulus whenever heard. The responses were noted and the average aided thresholds for frequencies 500 Hz, 1 kHz and 2 kHz were obtained.
The Categorical Auditory Performance (CAP) Scale is an eight-point nonlinear and hierarchical rating scale. It is administered for all cochlear implant candidates and has no specific age range and consists of scores between 0 and 7. This scale was used to rate auditory outcomes of CI in everyday life.
The Meaningful Auditory Integration Scale (MAIS) is a parent report scale that allows the examiner to evaluate the child's skills in meaningful, real-world situations and it can be assessed for even children above one year of age. This scale utilizes 10 probes and gathers auditory behavioural information based on the child’s device use. Each of these 10 questions consists of five different choices ranging from 0-(Never) to 4 (Always). The parent was asked to report the most appropriate choice regarding whichever describes the child best. The total scoring was given out of 40.
The Picture speech identification test for children with hearing impairment in Tamil was used to assess speech perception. The stimulus was presented one by one at a presentation level of 50 dBHL and the children were instructed to respond to the task, by pointing to the picture that represents the word presented. The child was given a score of 1 for every correct response and 0 for an incorrect response. Responses were later converted to percentage values.
Speech Intelligibility Rating (SIR) Scale is a five-point hierarchical scale globally used to measure the speech intelligibility of cochlear implant recipients. It ranges from “unintelligible speech” to “speech that is intelligible to all listeners”.
This test was utilized to measure the outcome of cochlear implantation with respect to speech, measuring the intelligibility of speech and the quality, and the analysis included the extent to which speech is understood and discriminated by the child in everyday situation.
The Communication Developmental Eclectic Approach to Language Learning (COMDEALL) was used to evaluate the speech and language skills of the children. The Communication DEALL Developmental Checklist (CDDC) was developed to carry out assessments of the children enrolled into the Communication DEALL programme. This checklist is generally used to assess developmental skills in 8 domains at 6-month intervals from 0 to 6 years of age.
Testing in each domain was terminated at the chronological age of the child. The receptive and expressive language skills, both of which fall under the major domain of language skills were then rated accordingly.
The data obtained from the 40 children across the three different groups were subjected to statistical analysis. Mean scores were obtained to evaluate and compare the performance outcome of the test battery used across the age groups. One-way ANOVA was used to calculate the test of significance using SPSS 26.0 software.
Results
Performance of Auditory Skills across all the Three Age Groups
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Aided Audiogram
The mean aided pure tone average (PTA) threshold was the lowest (33.1 dBHL) in Group I (0–2 years), 37.3 dBHL in Group II (2.1–4 years) and 39.2 dBHL in Group III. The findings of the current study reported that the mean aided thresholds of Group I (0–2 years) was (p < 0.01) than the other two groups.
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Categorical Auditory Perfromance Scale (CAP)
The mean scores indicated that when compared to children who were implanted late (Group II- 2.1–4 years and Group III- 4.1–6 years), children implanted between (0–2 years) displayed higher rating indicating better performance. The mean CAP scores in Group I (0–2 years) were 5.5, 4.7 in Group II (2.1–4 years) and 4.5 in Group III (4.1–6 years). Children implanted between 0–2 years, which is Group I (p < 0.01) showed improved performance results in CAP Scale than the other two groups.
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Meaningful Auditory Integration Scale (MAIS)
The mean scores of the MAIS questionnaire were determined across the three implant age groups. Like the other tests, MAIS scores were also comparatively higher in Group I (0–2 years). The mean score for Group I (0–2 years) was 33.9, 30.6 for Group II (2.1– years) and 29.2 for Group III. There was significant difference in MAIS scores across the three age groups (p < 0.01).
Performance of Speech Perception, Intelligibility and Speech-Language Skills Across All the Three Age Groups
Performance of speech perception skills was evaluated by calculating the mean scores of the Picture speech identification test in Tamil across the three age groups. The mean scores obtained for Group I (0–2 years) was 93.2%, 85.3% for Group II (2.1–4 years) and 71.2% for Group III. Similar to MAIS scores, this test also showed significant difference (p < 0.01) across the three age groups (Fig. 2).
Fig. 2.
Percentage scores for picture identification test across the three age groups
Performance of speech intelligibility skills was evaluated by calculating the mean scores of the Speech Intelligibility Rating (SIR) Scale across the three age groups. The mean score in Group I (0–2 years) was 3.9, 3.2 in Group II (2.1–4 years) and 2.9 in Group III. The findings indicated that the performance of Group I (0–2 years) was better compared to the other two groups.
Performances of speech and language skills were evaluated by calculating the mean receptive and expressive language scores of the Communication Developmental Eclectic Approach to Language Learning (COMDEALL) test across the three age groups. The mean receptive language score for Group I (0–2 years) was 56.6, 54.0 for Group II (2.1–4 years) and 49.7 in Group III. The mean expressive language score for Group I (0–2 years) was 50.7, 45.4 for Group II (2.1–4 years) and 41.9 for Group III. Qualitatively, it was observed that Group I (0–2 years) achieved ceiling effect in receptive language skills. Hence, it can be noted that the mean receptive and expressive language scores in COMDEALL are better in Group I which is the early implant group. It can also be further be noted that the performance of Group II is better than Group III. Despite these findings, the COMDEALL test RLA and ELA did not indicate any difference statistically.
Correlation Between duration of Implant Use and Performance of Auditory, Speech and Language Skills
The duration of implant use was compared with auditory, speech perception and intelligibility skills indicated that, children with implant usage of more than six years demonstrated higher performance. Although, there was no statistical difference between the duration of implant use and performances in each of these areas, it was observed that as the duration of implant use increased, there was significant improvement in speech and language skills. Also, both receptive and expressive language showed significant difference (p < 0.01). These findings indicate that as the duration of implant usage increased, speech and language skills also improved over time.
Discussion
The data of the current study constitutes a preliminary analysis of the outcomes of cochlear implant in 40 children who received cochlear implant between 11 months to five years of age. The overall results of auditory skills suggested improved performance in children implanted earlier in life. Age of implantation is directly related to the survival, physiology and function of the spiral ganglion cells [9]. Based on the age at implant, the effect of deprivation and plasticity can be interpreted via post CI performances. Young children learn language through incidental learning or overhearing. Over hearing requires threshold level as low as 30–35 dBHL. The children in Group I (0–2 years) had an average aided threshold that falls within this range of thresholds required to hear soft speech. Aided thresholds at 30–35 dBHL help improve speech perception and also phonological production and facilitates incidental language acquisition and the use of spoken communication [10]. This finding emphasizes that fact that good audition facilitates spoken language acquisition in young children with CI.
Children with CI develop speech recognition immediately following implantation and these skills develop over a period. This growth is more rapid in children implanted early in life due to developmental plasticity of the auditory system, which signifies improved perceptual scores. [11].
Speech perception skills were evaluated by administering the Picture speech identification test for children with hearing impairement in Tamil. The findings indicated improved performance in those implanted earlier (0–2 years) when compared to the other two age groups. CI allows the Primary Auditory Cortex (PAC) to achieve maturation that is dependent on sensory experience, although not as precisely as it is in the absence of SNHL. There also exists a positive correlation between speech perception and a low resting activity in the PAC prior to implantation in the prelingual deaf. This suggests that the PAC and other higher order auditory centres have potential for changes related to plasticity which is evident with continued improvement in the auditory performance with growing experience in CI. Most prominent clinical outcomes for cochlear implant patients occurs more in the immature auditory cortex [9].
Children implanted around two years of age show improvement in open-set speech perception, language acquisition and speech production. They demonstrate near normal language skills in school and achieve ceiling level unlike the later implanted children [12, 13]. Three years following implantation, even the later-implanted children will be able to achieve comparable speech perception abilities with intensive training and patience [14].
In the current study, although the children implanted early performed well, all the groups had a score of above 75% in the closed set test. This evidence points in the direction that children implanted later than two years will eventually progress. This findings highlights the fact that individuals with long-term prelinguistic deafness can achieve significant open-set speech understanding with a cochlear implant, although there is a wide range of performance variability across patients. Many children in Group I (0–2 years) achieved ceiling in this test, which further indicates that they have progressed in the perceptual skills and are ready for open set speech perception evaluation.
The speech intelligibility outcomes indicated that children implanted younger than 2 years of age had better performance than children who underwent implant later (2.1–4 years and 4.1–6 years). Auditory feedback helps these children understand the consequences of their articulatory gestures and helps in comparing sounds produced by other speakers. This feedback then provides information for monitoring the ongoing speech production for detecting errors if any [15].
The Communication Developmental Eclectic Approach to Language Learning (COMDEALL) test tool was administered to assess the speech and language skills. The results of the current study indicate that the mean receptive and expressive language scores are advanced in children who are implanted earlier (0–2 years) than those implanted later (2.1–4 years) and (4.1–6 years). When children are implanted earlier, the probability for the child to progress in its auditory and language skills is higher. As age of implantation increases, the children start to lag further in these performance areas when compared to their age matched peers [9, 16]. The children implanted early in life, score better when compared to children implanted later in terms of higher language ability to function in daily life [17]. The foremost reason behind early implant children having improved skills is due to reduced auditory deprivation period.
Conclusion
The results reinforce the fact that children implanted between 0–2 years (Group I) of age demonstrated increased performance in all tasks including audition, speech perception and intelligibility as well as speech and language when compared to the other two groups. The study highlights the importance of a test battery approach that encompasses various developing skills that is vital to follow progress of the child. Children with cochlear implant continue to improve with consistent device usage and with appropriate mapping, habilitation and training. This re-establishes that children with CI will be able to achieve an optimum level of performance in par with their hearing peers in all aspects of life.
Funding
No funding was obtained for the study.
Declarations
Conflict of interests
There was no conflict of interest among the authors.
Ethical approval
The study was conducting after approval for the institutional ethics committee of SRIHER (Ref.no: CSP/19/MAR/76/127).
Footnotes
Publisher's Note
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Contributor Information
Sri Ranjani Vaideeswaran, Email: ranjani.shekar96@gmail.com.
Dawson Gladys Prathiba, Email: prathiba.dawson@sriramachandra.edu.in.
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