Keywords
cochlear Implantation - receptive language - expressive language - language assessment
- REELT-3
Introduction
Cochlear implantation (CI) is globally considered as the standard intervention for
severe-to-profound sensory-neural hearing loss in adults and children.[1]
[2]
[3] Children with congenital or acquired deafness in the early years of life are at
a risk of having delayed language comprehension and expression development.[1]
[4] Occurrence of congenital deafness restricts access to acoustic and phonetic elements
essential for speech understanding.[5] The outcome of CI, owing to increased access to the sound provided by it, helps
children with deafness to develop language comprehension and expression skills. However,
owing to individual and environmental variability, long term outcomes in children
with CI are not uniform.[6]
[7] The age of implantation, surgical techniques, mode of therapy, education level of
parents, degree of hearing loss, continuation of therapy, and family involvement are
some of the common factors that influence the CI outcomes.[2]
[8]
[9]
[10]
[11]
[12]
The language learning outcome assessment in children with CI is an effective way to
comment on the success of CI intervention.[3]
[13] The duration of CI use in early implanted children is a robust predictor of language
outcomes; a child with longer CI usage duration is likely to perform better than children
with shorter CI duration.[6]
[14] The development of language in children with CI has been studied using a longitudinal
design, in which language assessment was conducted for a group of children with CI
at certain intervals, such as 12 months after implantation,[15] 24 months,[1]
[16] 36 months,[11] 48 months,[6] and 60 months and beyond.[13]
[17] In such a scenario, post-CI language gain was compared across the baseline, which
is at the time of implantation, to the performance across certain intervals of CI
such as 1, 2, 3, 5, 10 and more years. There are varying results of CI success at
these intervals. Nicholas (2007) observed age matched improvement in expressive language
by 4.5 years in children who were implanted before 24 months and assessed at 6 and
18 months, respectively.[12] Connor (2006) investigated vocabulary and speech production outcomes in children
with CI semiannually in the 1st year and once for the next 5 years and reported that children who received CI before
30 months reflected an early burst of language improvement better than children who
implanted at a later age.[14] Geers and Sedey (2011) also found that over 70% of children with more than 10 years
of CI usage performed closer to children with normal hearing (NH) on single word vocabulary,
isolated sentence comprehension and reasoning tasks.[16]
These findings suggest that there is lack of consistency regarding post-CI assessment
interval duration. It ranged from 3 months to 5 years intervals. No study was found
in which language outcomes in children with CI was evaluated at fixed, regular intervals
using suitable age-matched children with CI under a counterbalanced, cross-sectional
design. It is hypothesized that language assessment of children who were implanted
at early age, if assessed periodically at fixed intervals, may yield better language
outcomes because the evaluation outcome will also help to fine tune the language intervention
program. The findings of this study will facilitate better understanding of the trajectory
of language growth in children with CI as well in customizing the speech-language
stimulation plan as per the existing needs of the children within the sensitive period
of language learning. Therefore, the aim of the present study was to evaluate the
language learning outcome at six-monthly post-CI intervals using revised receptive
expressive emergent language test-3ed. (REELT-3), which was recently tested and validated
for Hindi speaking children with CI.[18]
Furthermore, most of the studies of CI language assessment and outcome have been done
in native English-speaking children, which cannot be directly applied to children
speaking different languages across the world due to structural linguistic variations
across languages. Several studies have reported that non-English speaking children
were excluded from the language outcome assessment study due to linguistic variations,
which can be a major robust confounding factor.[3] Morpho-syntactic characteristics of Hindi, one of the widely spoken languages of
India, is more complex compared with English.[18] The morphology of nouns, pronouns, number, and gender agreement of nouns as well
as subject-verb agreement is more complex in Hindi as compared with English.[19] Recent studies suggest that there may be a variable sensitive period for different
levels of language.[20] However, until now, no study has been done to observe the development of language
comprehension and production abilities in Hindi-speaking children with CI in a periodic
manner and thus that was the another rationale of this study . It is hypothesized
that periodic evaluation of the language at an interval of 6 months will enable us
to know the language development pattern in Hindi speaking children with CI. Therefore,
the present study was designed to evaluate language comprehension and production abilities
in (a) Hindi-speaking children with CI; (b) two control groups of children with NH,
one with chronologically age-matched children and the other with chronological age
corresponding to that of CI activation; and (c) those with CI experience of up to
2 years at an interval of 6 months, such as 6, 12, 18, and 24 months of the time of
implant activation (TIA).
Materials and Methods
Participants
A total of 96 children with NH (22.3 ± 7.9 months, 48 boys and 48 girls) with no complaint
of speech, language, hearing, intellectual, and developmental delay, and 96 children
with CI (15.8 ± 6.7 months, 57 boys and 39 girls) participated in this study ([Table 1]). Another group was formed based on the TIA (14.6 ± 8.8 months); for instance, if
a child's CI activation was done at 2 years of chronological age and language assessment
was conducted at 3 years of chronological age, then, his TIA age was considered as
1 year ([Table 2]). Chronological age-matched controls were selected for the TIA group. All the participants
were within 36 months of age and were residents of Delhi, India and nearby regions.
([Table 1]) Data were collected over 2 years.
Table 1
Mean age, standard deviation, gender, and percentage of participants across gender
for normal hearing, children with cochlear implant and time of implant activation
groups
|
Children with normal hearing (NH)
(22.3 ± 7.9 months) n = 96
|
Children with cochlear implant (CI)
(15.8 ± 6.7 months) n = 96
|
Time of implant activation (TIA)
(14.6 ± 8.8 months)
n = 96
|
|
Boys
|
Girls
|
Boys
|
Girls
|
Boys
|
Girls
|
|
Number of Participants
|
48
|
48
|
57
|
39
|
57
|
39
|
|
Percentage of Participants
|
53.1%
|
46.9%
|
60.4%
|
39.6%
|
60.4.%
|
39.6%
|
Table 2
Mean and standard deviation of the age of time of implant activation groups (age in
months)
|
TIA age groups
|
Mean age
|
N (96)
|
Std deviation
|
|
0–6
|
5.95
|
24
|
3.34
|
|
7–12
|
11.5
|
24
|
4.22
|
|
13–18
|
17.0
|
24
|
1.86
|
|
19–24
|
21.45
|
24
|
2.43
|
|
Total
|
13.97
|
|
6.5
|
Abbreviation: TIA, time of implant activation.
Ethical standards and considerations were maintained and adhered to while selecting
the participants for this study. Institutional ethical approval was obtained before
the participant's recruitment (AUUP/IEC/2018-AUG/04). The family members/caretakers
of each participant were informed about the purpose and procedure of the study and
written consent was acquired. Participants under the NH category were selected based
on the following inclusionary criteria: target age of the language assessment tool
used in this study (REELT-3); age of the participants below 36 months with no reported
history of hearing loss, cognitive, or intellectual deficit, and Hindi as the primary
spoken language at home. For the CI group, the pure tone audiometry finding was more
than 85 dB in the better ear. There should not have been any known history of premorbid
neurological illness, psychological disorders, and no other significant sensory and/or
cognitive deficits for both groups. Children with CI using sign languages or whose
parents were deaf did not participate in this study. Children with NH were recruited
through a random sampling method and purposive sampling was used for the selection
of children with CI. Based on the CI usage duration, the children with CI were further
categorized under 4 categories based on implantation duration (a) between 0 and 6
months (b) 7 and 12 months (c) 13 and 19 months, and (d) 18 and 24 months.
Test Stimuli
Language comprehension and production were assessed using the REELT-3.[21] Sixty-six test items of the REELT-3 were chosen for this study. The components of
REELT-3 are 2-fold (a) receptive language and (b) expressive language. In this test,
language milestones were used as test items, which were arranged in gradually increasing
order of complexity. Some examples of the 66 test items of the REELT-3 are mentioned
ahead. In expressive language, #7 “When hearing voices, does your baby ever vocalize
back”? to receptive language #25 “Does your baby respond to simple commands or requests
like ‘Come here!’ or ‘Let's go!’?” The response was collected in a binary manner,
that is, either ‘Yes’ or ‘No’.
Procedure
The REELT-3 was used to evaluate the receptive and expressive language of children
with CI and NH. Recently, we have published the validation of the REELT-3 in Hindi
Speaking children with CI.[18] Language ability score (LAS) was obtained for both NH and CI groups. The LAS is
the combined score of the receptive language ability score (RLAS) and the expressive
language ability score (ELAS), which is the standard score obtained after getting
a total correct response out of the 66 questions of the REELT-3 under the receptive
and expressive categories. Responses were obtained as per the feedback provided by
the mother/caregiver as well as, based on the direct observation and interaction during
the assessment. The test was administered, analyzed, and interpreted by trained intern
volunteers of audiology & speech therapy. Participants' responses were analyzed and
a score of ‘1’, or ‘0’ was given for every correct response with or without prompt
and incorrect/no response even after prompt response, respectively.[21] As the questions of the REELT-3 were categorized at an interval of 6 months, the
average LAS for the NH group across each 6 months interval, such as 18 to 24 months,
25 to 30 months, and 31 to 36 months, were obtained and considered as a control group.
The LAS of the CI group was obtained at two levels (a) overall LAS of the CI group
(of 96 participants), and (b) LAS across four post-CI duration (of 0–6, 7–12, 13–18,
and 19–24 months of CI usage).
Data Analysis
The response of each participant was coded, arranged, and analyzed using the IBM SPSS
Statistics for Windows, Version 21.0. (IBM Corp., Armond, NY, USA). One-way and two-
way analysis of variance (ANOVA) tests were used to check whether LAS across three
groups (NH, CI, and TIA) and across four post-CI durations varied significantly or
not. Tukey's HSD posthoc analysis was done to check out specific relations across
the four CI implant durations.
Results
The mean LAS of Hindi speaking children with CI, NH, and TIA was obtained and it was
compared across each other. The one-way ANOVA test was used to evaluate whether the
language performance of these three groups differ significantly from each other. A
significant difference in language performance was obtained across the TIA, NH, and
CI groups (F (2, 285) = 79.530, p = 0.001, ηp2 = 0.358) ([Fig. 1]). Moreover, Tukey's HSD posthoc analysis was done to test the significance between
NH and CI, NH and TIA, TIA, and CI groups. It was observed that language performance
differed significantly across all three conditions; (a) the language performance of
children with NH was significantly better than that of children with CI (F (1, 190) = 21.89,
p = 0.001, ηp2 = 0.495); (b) similarly, group-wise the children with up to 2 years
of TIA performed poorer than the age-matched children with NH[14] for language performance task (F (1, 190) = 15.89, p = 0.001, ηp2 = .289), and (c) children with up to two years of TIA performed better
on language performance tasks than the children with CI (F(1, 190) = 6.273, p = 0.004, ηp2 = 0.037) ([Fig. 1]).
Fig. 1 Bar graph depicting language ability score across normal hearing, cochlear implant
and time at implantation activation groups. * inferring statistical significance (p < 0.001); Abbreviations as in the text.
The LAS of the TIA group was compared across 4 CI usage windows, that are 0 to 6 months,
7 to 12 months, 13 to 18 months, and 19 to 24 months. One-way ANOVA analysis was done
to test whether the language performance of these four groups significantly varied
from each other. It was observed that language performance across four CI usage duration
was significantly different across each other (F (3, 92) = 6.620, p = 0.001, ηp2 = 0.178) ([Fig. 2]).Tukey's HSD posthoc analysis was done to identify the rate of improvement across
four CI usage durations and to test whether these durations differed significantly.
It was observed that the language performance of the TIA group having more than 18
months of CI usage was significantly higher than TIA groups of 0 to 6, 7 to 12, and
12 to 18 months. However, no significant difference was observed between children
having CI usage experience of 7 to 12 months and 13 to 18 months ([Fig. 2]).
Fig. 2 Bar graph showing language ability score across four groups of time of implant activation
(in months). * inferring statistical significance (p < 0.01); Abbreviations as in the text.
Besides, the LAS of children of the TIA group from 0 to 2 years of CI usage were compared
across age-matched children with NH. The two-way ANOVA revealed that the language
performance of children with CI for 0 to 6 months durations was significantly lower
than children with NH (F (3, 92) = 30.1, p = 0.008, ηp2 = 0.028) ([Fig. 3]), while in the 18 to 24 months group, the language performance in the CI usage approached
that of the NH group (F (3, 92) = 8.63, p = 0.19, ηp2 = 0.028). Language development pattern in boys and girls with CI was
also evaluated for the NH, CI, and TIA groups. The two-way ANOVA test was computed
to test whether the language performance of children with CI was different from each
other across gender during four phases of assessment at 6 months interval. No significant
difference in overall language gain across boys and girls was obtained for NH, CI,
and TIA (F (3, 92) = 1.73, p = 0.505, ηp2 = 0.002) ([Fig. 4]).
Fig. 3 Bar graph reflecting language ability score across normal hearing, cochlear implant
and time of implant activation groups across gender. * inferring statistical significance
(p < 0.05); Abbreviations as in the text.
Fig. 4 Bar graph reflecting language ability score of children with normal hearing across
children with cochlear implant of time of implant activation groups across four assessment
conditions at an interval of 6 months. * inferring statistical significance (p < 0.05); Abbreviations as in the text.
Similarly, the language outcome was tested across the socioeconomic-educational perspective.
Parents of the CI group who had less than 12 years of formal education were compared
across more than 12 years of educated parents. The one-way ANOVA test was computed
to test whether the language performance of these three groups differed, and it was
observed that the educational background of parents does not significantly influence
language outcomes (F (3, 92) = 2.05, p = 0.937, ηp2 = 0.031). Parents of the CI group whose monthly income was lower than
the Indian Rupees 10,000 were compared to parents who earned more than the Indian
Rupees 10,000. The one-way ANOVA test was computed to test whether the language performance
of these two groups differed significantly, and it was also observed that the financial
background of parents does not influence language outcomes significantly in children
with CI (F (3, 92) = 2.49, p = 0.351, ηp2 = 0.076).
Discussion
In the present study, language comprehension and expression abilities were tested
using the REELT-3 to compare NH, CI, and TIA Hindi speaking children. It was observed
that the LAS of the CI group was significantly different compared with that of the
NH group; however, no significant difference was obtained across the CI & TIA and
TIA & NH groups. Thus, it can be inferred that the language development in the TIA
group occurred in the same patterns as that of age-matched NH children. The mean age
of the TIA group was 21.45 months, which suggests that auditory stimulation of more
than 14 months is critically required and enough to bridge the gap in language performance
between the CI and NH groups. These findings suggest that the prolonged auditory period
in children with CI increases the morphological and phonological awareness skills
that are requisite for language development and expression.[1]
[14] Moreover, longer duration of CI usage enhances mother-child interaction and helps
in building additional social-cognitive connection with the surroundings, which is
essential for language development.[14]
Depending on the duration of CI usage, the development of language learning was also
measured across four time frames, between 0 and 6 months; 7 and 12 months; 13 and
19 months; and 18 and 24 months. The results revealed that the language performance
of CI children increased significantly after 18 months of CI usage compared with the
other three time frames. Moreover, a significant difference was also observed for
language development between 0 and 6 months and 13 and 18 months of the TIA group.
This finding suggests that a minimum of 1 year is required to observe a significant
difference in language development among various TIA groups, thus justifying the need
for early implantation.[12]
[22]
[23] Early implantation ensured early access to sound for the CI children resulting in
a shorter sound deprivation period, which is required for language development.[11] It was also observed that early CI ensures auditory neural reorganization corresponding
to exposure of sound or verbal input.[24]
[25] These findings also support the existence of an early sensitive period through early
and ongoing plasticity of central auditory pathways for receptive and expressive language
learning in children with CI.[14] Furthermore, the present study also supports the age range of less than 2.5 years
as the most sensitive critical age for neuroplasticity and central auditory nerve
development responsible for the growth of language, as the mean age of the TIA group
in this study was 14.6 months.[25]
[26] However, the critical time range of less than 2.5 years may vary for different speech
and language components.[27] Also, the results revealed that even after 24 months of CI use, the group-wise gap
on language performance tasks was not bridged completely between the Hindi speaking
CI and NH groups. However, after 18 months of CI usage, the language performance of
children with CI appeared in the range of that of children with NH. Owing to morphosyntactic
complexity, especially in person, gender, number, subject-verb agreement, etc., language
learning in children with CI cannot completely approach the learning abilities of
children with NH. This further justifies the need for a longitudinal study for more
than 24 months of activation of CI.
Furthermore, the language performance was also compared among the CI, TIA, and NH
groups across gender, family income, and parental education, separately. The rationale
for doing such analysis was to check whether these confounding variables have any
impact on the outcome of the present study. No significant difference was observed
for any of these three conditions. Prolonged CI usages and early implantation enables
re-networking of the central auditory pathway, which is essential for intact language
comprehension and production.[25] Thus, it may be possible that demographic-related issues, such as gender, family
income, and parental education, would not have impacted the language learning outcomes.
Moreover, although the status of language in children in the CI and NH groups was
quantified using parents' feedback along with direct observation and interaction,
the potential bias in the parents' information may not be ruled out completely.
Conclusion
The present study reveals that language development in children with CI improves significantly
during the 2nd year of CI usage. The present findings justify the need for early implantation to
ensure a reduced sound deprivation phase. Periodic assessment of language outcomes
at an interval of 6-months in the children with CI can facilitate the understanding
of the pattern and trajectory of language development. The inclusion of more language
domains for assessment beyond 2 years, using a longitudinal design, may yield better
outcomes. From a theoretical point of view, this study allows us to understand the
nature of linguistic difficulties in children with CI that may manifest across the
different duration of CI usage across languages. Clinically, the dynamics of language
development in children with CI can be used as feedback in developing a target-based
therapeutic intervention plan.
