The Effect of Age at Cochlear Implantation on Speech and Auditory Performances in Prelingually Deaf Children

Abstract

To understand the effect of age at implantation on speech and auditory performances of 74 prelingually deaf Indian children after using cochlear implants for 3, 6 and 12 months. We also evaluate the causes of late implantation in this population. Seventy four children who underwent cochlear implantation from December 2013 to December 2015 in the Department of Otorhinolaryngology and Head Neck Cancer in SMS Medical College, Jaipur were participated in this study. To compare the efficacy of cochlear implant, candidates are classified into 2 groups according to the age at the time of implantation: 1–4 years and 4.1–7 years. The sample size is 37 in both age groups. Their auditory performance and speech intelligibility were rated using the Revised Categories of Auditory Perception scales, Speech Intelligibility Rating scales and Meaningful Auditory Integration Scale. The evaluations were made before implantation and 3, 6 and 12 months after implantation. The scores when compared in both the groups revealed that the results were comparable and significant after 12 months of follow up while the scores were not significant after 3 and 6 months. The results were statistically significant when baseline is compared with different postoperative stages. The children implanted before the age of 4 years had significantly better auditory and linguistic performances. At least 12 months of audio-verbal rehabilitation and speech and language therapy are required to compare the effects of cochlear implant in any set of children. Our study shows that hearing impaired children who receive cochlear implantation below 4 years of age acquires better auditory ability for developing language skills.

Introduction

Communication is the key to survive and to express the feelings and ideas with others in this world. Those who are not born with the gift of hearing have a boon of cochlear implants. Cochlear implantation has become an accepted treatment paradigm for individuals who have bilateral severe to profound SNHL [1–3]. If an early intervention is not done in severe and profound young children, it will lead to poor speech perception and production skills [4–7]. The overall prevalence of congenital hearing disorder is 1–3/1000 new-borns [8]. Congenital sensorineural hearing impairment has been estimated at 1.2–5.7/1000 live births [9–13]. The largest population having hearing impairment goes to our continent with 2.6 affected in 1000 live births every year [14]. The evaluation of the speech perceptual abilities and the speech intelligibility of young deaf children needs adapted tests and long-term follow-up after implantation. They are indicated in young patients with profound and severe hearing loss who do not benefit from conventional hearing aids, have no medical contraindications and do not harbour unrealistic expectation [15]. Multichannel cochlear implantation of these children permits significant improvement in both speech perception and production following implantation [4–7]. The ability to perceive speech could be considered the single most important primary outcome measure of cochlear implantation [16]. Approximately 50,000 cochlear implant surgeries are performed per year worldwide based on manufacturer revenue estimates [17].

Children with profound sensorineural hearing loss are at significant risk for serious speech and language delays that can impact their communication, academic and social development [18]. During the early 1990s the factors found to be associated with good performance were duration of deafness, age at onset of deafness and age at implantation [19, 20], duration of implant use, length of daily device use and preoperative level of residual hearing.

The period from first 5 years of life including the in utero development is critical for the development of speech and language; hence early identification and assessment of hearing loss can result in early rehabilitation which can result in development of near normal speech with no requirement of special education [21]. In this period, the brain has plasticity to adapt the auditory information associated with meaningful auditory performance and language. The association between age at implantation and child outcomes is complex because a child’s age, length of device use, family education, mode of communication at home, socioeconomic status and age at implantation are highly related.

Seventy percent of Indian population resides in rural area. Lack of knowledge and awareness about health and poor health care services among them contributes to the late presentation of deafness. Even if the deafness is diagnosed, people waste their time in unnecessary exercises prescribed by local practitioners. The potential negative consequences of later implantation are becoming clear [22, 23]. Theoretically, earlier sensory experience should provide benefit in sensory development as well as in cross-modal and cognitive development. An early sensory input provides advantage of using the period of neural plasticity [24, 25].

Furthermore, the rate of auditory skills development seems to be increasing as cochlear implant technology improves and as children is implanted at a younger age. Early studies reported significant increases in the discrimination of non-segmental speech cues after only 6 months of implant use. However, significant increases in the discrimination of vowels and consonant features were not evident until 1.5 years of cochlear implant experience and auditory-only open-set skills continued to improve long after this time period. Recent studies have shown that many children achieve open-set speech recognition within the first year of device use and continue to develop over time [26].

Materials and Methods

Present study is a Hospital based observational prospective study which included prelingually deafened candidates, who attended our outpatient department and underwent cochlear implantation in Department of Otorhinolaryngology and Head Neck Surgery, SMS Medical College, Jaipur from December 2013 to December 2015. 74 patients of age group 1–7 years underwent cochlear implantation in the study period. A detailed history was obtained to identify the etiology, background of the family, their approach to the identification and intervention of the deafness. To compare the efficacy of cochlear implant, candidates are classified into 2 groups according to age at the time of implantation: 1–4 years and 4.1–7 years. The sample size is 37 in both age groups. Audiological and speech evaluation was performed preoperatively and 3, 6, and 12 months postoperatively using the Revised CAP, MAIS and SIR scales so that each subject could be self-compared, allowing for a single subject repeated measures design. The questionnaires were filled preoperatively and at the further follow ups by enquiring the parents about the candidate’s status. The data of auditory performance was gathered from the respective audiologist involved in the rehabilitation programme. The excluded candidates are those who are postlingually deaf, prelingually deaf with mental retardation and Bilateral cochlear implantees.

Statistical Analysis

The speech and auditory performance scores obtained at 3 stages of 3, 6 and 12 months after the cochlear implantation were considered as the dependent variable. The gathered data was analysed through the SPSS statistical software. We started by taking out the mean of the speech and auditory performance scores obtained at 3, 6, and 12 months after the implantation. The data did not follow the normal distribution; nonparametric tests were used for comparison. In fact, regarding the dependability of the individuals’ data, the Friedman nonparametric test together with Wilcoxon test was used to compare the difference between the auditory and linguistic performances scores.

Results

In this study of 37 patients in both the age groups, the male to female ratio in 1–4 year age group is 1.17 and in 4.1–7 year age group it is 3.62. 4% of total patients had Waardenburg syndrome. 9 cases (12.1%) had family history of deaf-mutism. Acquired causes were the most common cause of hearing loss contributing 51.3% of the study population. 32.4% were of unknown etiology and 16.2% were of hereditary causes. Perinatal factors were the predominant factors for acquired deafness. There is no effect of etiology of hearing loss on the results after cochlear implantation.

13.5% of the study population had cochleovestibular anomaly in radiological imaging, out of which 4% had ossification of labyrinth. 4% had incomplete cochlear turn and 9% had enlarged vestibular aqueduct. Significant intraoperative observation in the form of CSF gusher was observed in 6.7% and forward lying sigmoid sinus was present in 4%. Seventy patients (94.5%) had right side cochlear implantation whereas left side implantation was done in four cases (5.4%). Cochleostomy in our study was performed by extended round window approach in 24.3% and by separate cochleostomy, anteroinferior to round window in 75.6%.

In 1–4 year age group, 15 cases were using hearing aid up to 1 year, while in 4.1–7 year age group it was 13. 13 cases in both the age groups used hearing aid for 1–2 year. 3 cases were using hearing aid up to 2–3 years, while in 4.1–7 year age group it was 6. 6 cases in 1–4 year age group and 5 cases in 4.1–7 year age group did not use hearing aid at all (Fig. 1).

Fig. 1.

Data showing number of Hearing air users in both the groups

In 1–4 year age group, 12 cases had speech therapy for up to 1 year, while in 4.1–7 year age group it was 13. 13 cases in first group and 12 in second group used it for 1–2 year. 4 cases in both the groups used it for 2–3 years. 8 cases in both the group did not use speech therapy at all (Fig. 2).

Fig. 2.

Data showing the children who used speech therapy in both the groups

The postoperative mean CAP scores in both the groups were statistically significant at 3, 6 and 12 months. When compared in both the groups, the results were comparable but not significant after 3 and 6 months while the results were significant after 12 months (Tables 1, 2). In 12 months a score of more than category 8 was achieved by 56.7% of the implantees in first group and 32.4% of the implantees in second group (Table 3). Children who were implanted early in childhood had more rapid language growth rates than children implanted later in childhood. The results were statistically significant after 12 months follow up (Fig. 3).

Table 1.

Mean CAP score in 1–4 year age group

CAP	Mean	S.D.	P value (Friedman test)	P value (Wilcoxon test)
Preoperative	0.351	0.978	0.000	0.000
Postoperative 3 m	2.459	0.557
Postoperative 6 m	5.432	0.765
Postoperative 12 m	7.95	1.84

Table 2.

Mean CAP score in 4.1–7 year age group

CAP	Mean	S.D.	P value (Friedman test)	P value (Wilcoxon test)
Preoperative	0.3	0.62	0.000	0.000
Postoperative 3 m	3.324	1.749
Postoperative 6 m	5.14	2.14
Postoperative 12 m	6.91	1.48

Table 3.

Comparison of revised CAP scores in both the age groups

Revised CAP	1–4 years	4.1–7 years	P value
< 8	16 (43.3%)	25 (67.6%)	0.05
> 8	21 (56.7%)	12 (32.4%)

Fig. 3.

Line diagram demonstrating the CAP Score in both the age groups. Children who were implanted early in childhood had more rapid language growth rates than children implanted later in childhood

The postoperative mean MAIS scores in both the groups were statistically significant at 3, 6 and 12 months. When compared in both the groups, the results were comparable but not significant after 3 and 6 months while the results were significant after 12 months (Tables 4, 5). In 12 months a score of more than > 35 was achieved by 89.1% of the implantees in first group and 56% of the implantees in second group (Table 6). The results were statistically significant after 12 months follow up (Fig. 4).

Table 4.

Mean MAIS score in 1–4 year age group

MAIS	Mean	S.D.	P value (Friedman test)	P value (Wilcoxon test)
Preoperative	2.135	4.565	0.000	0.000
Postoperative 3 m	14.89	7.90
Postoperative 6 m	25.16	8.71
Postoperative 12 m	37.22	7.05

Table 5.

Mean MAIS score in 4.1–7 year age group

MAIS	Mean	S.D.	P value (Friedman test)	P value (Wilcoxon test)
Preoperative	2.568	6.003	0.000	0.000
Postoperative 3 m	15.72	8.15
Postoperative 6 m	24.86	7.97
Postoperative 12 m	33.2	6.24

Table 6.

Comparison of MAIS scores in both the age groups

MAIS score	1–4 years	4.1–7 years	P value
< 35	4 (10.9%)	16 (44%)	0.004
> 35	33 (89.1%)	21 (56%)

Fig. 4.

Line diagram demonstrating the MAIS Score in both the age groups. Children who were implanted early in childhood had more rapid language growth rates than children implanted later in childhood

The postoperative mean SIR scores in both the groups were statistically significant at 3, 6 and 12 months. When compared in both the groups, the results were comparable but not significant after 3 and 6 months while the results were significant after 12 months (Tables 7, 8). In 12 months category 5 has been achieved by 37.8% of the implantees in 1–4 year age group and 5.4% of the implantees in 4.1–7 year age group (Table 9). Children who were implanted early in childhood had more rapid language growth rates than children implanted later in childhood (Fig. 5). In 1–4 year age group 37.8% of the implantees achieved category 5, 35.1% achieved category 4, 24% achieved category 3 and 2.7% achieved category 2 in 12 months whereas in 4.1–7 year age group 5.4% of the implantees achieved category 5, 35.1% achieved category 4, 21% achieved category 3 and 16.2% achieved category 2 in 12 months.

Table 7.

Mean SIR score in 1–4 year age group

SIR	Mean	S.D.	P value (Friedman test)	P value (Wilcoxon test)
Preoperative	1.03	0.164	0.000	0.000
Postoperative 3 m	1.67	0.747
Postoperative 6 m	2.48	0.960
Postoperative 12 m	4.08	0.862

Table 8.

Mean SIR score in 4.1–7 year age group

SIR	Mean	S.D.	P value (Friedman test)	P value (Wilcoxon test)
Preoperative	1.08	0.28	0.000	0.000
Postoperative 3 m	1.7	0.78
Postoperative 6 m	2.4	1.1
Postoperative 12 m	3	1.2

Table 9.

Comparison of SIR in both the age groups

SIR score	1–4 years	4.1–7 years
5	14 (37.8%)	2 (5.4%)
4	13 (35.1%)	13 (35.1%)
3	9 (24%)	8 (21%)
2	1 (2.7%)	6 (16.2%)

Fig. 5.

Line diagram demonstrating the SIR Score in both the age groups. Children who were implanted early in childhood had more rapid language growth rates than children implanted later in childhood

In our study, significant association was found between age at implantation and linguistic performance after 12 months.

Discussion

All the patients in our study had undergone immunization against Pneumococcus, Meningococcus and Haemophilus Influenzae type B at least 2 weeks prior to surgery.

The mean age at the time of the implantation was 3.25 ± 0.73 years in the 1–4 year age group and 5.59 ± 0.78 years in the 4.1–7 year age group. This is in concordance with a study by Sayed Basir Hashemi [27] in which mean age at the time of the implantation was 41.77 + 13.1 months ranging from 24 to 84 months. There was no sex predilection in the earlier implanted group due to parental awareness, no discrimination between the male and female, early realization and hence early intervention which has contributed to the results as well. While in the later implanted group there is male preponderance and majority belonged to rural area, when the deafness is diagnosed by the parents, only males were given importance. The mentality of male dominant society plays an unsupportive role for the female child. Socioeconomic status of the patient also contributed to the results, children belonging to the families from higher socioeconomic status presented earlier for diagnosis & intervention.

The ratio of male to female was 1.17 in 1–4 years age group and 3.62 in 4.1–7 years age group, which is statistically significant. This ratio was 1.66 in a study by Calhau [28] with males contributing 62.5% and females were 37.5%; while in a study of 70 cases by Iype et al. [29], number of male and female cases were approximately equal with the male to female ratio being 1.06:1. The results of the present study showed that at 3, 6, and 12 months after the implantation, there was no significant association between sex, and the children’s auditory and speech performance.

Acquired causes were the most common cause of hearing loss contributing 51.3% in all the cases. Among which 28% cases presented with prenatal factors responsible for prelingual deafness. Most common prenatal risk factors were infections and use of ototoxic drugs. Perinatal factors were responsible in 52% of the population which were the predominant factors for acquired deafness among prelingually deaf child. Considering the perinatal factors, it was observed that low birth weight, birth asphyxia and prematurity was the important risk factor. 20% of the population were having postnatal factor responsible for the cause. This is in concordance with the study carried out by Iype et al. [29] in which prenatal risk factor was identified in 45.71%; perinatal factors were found in 71.42%, among which most important risk factor was birth asphyxia predisposed by prematurity and low birth weight was the most common.

All patients in both the age groups underwent preoperative and postoperative audiological and speech assessment using CAP, MAIS and SIR scales. The study also laid emphasis on the comparison of the outcomes with respect to the protocols followed in the institution and the protocols given in the guidelines given in the Cochlear Implant Group of India (CIGI). The mean of the auditory and speech performances of the children after cochlear implantation were computed after 3, 6 and 12 months.

The outcome of the auditory performance was measured using the Revised Category of Auditory Performance (CAP) score described by The Shepherd Centre based on Nottingham CI Program. The extent of auditory perception, in terms of utility of auditory mechanisms to pursue day to day tasks was assessed. The ability to discriminate and understand speech with or without lip reading was also assessed and the results were categorized accordingly and a score was given, taking into account the number of months taken to achieve it. While assessing CAP score, we found that preoperative mean score in 1–4 year age group and 4.1–7 year age group were 0.35 ± 0.98 and 0.3 ± 0.62 respectively. In first group, the postoperative scores at 3, 6 and 12 months were 2.46 ± 0.56, 5.43 ± 0.77, and 7.95 ± 1.86 respectively. In the second group the postoperative scores at 3, 6 and 12 months were 3.32 ± 1.75, 5.14 ± 2.14 and 6.91 ± 1.48 respectively (Tables 1, 2). The postoperative mean CAP scores in both the groups were statistically significant at various stages with increasing order according to Friedman test. Wilcoxon Signed Rank test (WSR test) for pre-op and post-op comparison showed statistically significant results when baseline was compared with different postoperative stages. The CAP scores when compared in both the groups revealed that the results were comparable but not significant after 3 and 6 months while the results were significant after 12 months (Mann–Whitney Rank Sum Test). In first group 56.7% of the implantees achieved a score of more than 8 in 12 months while in second group 32.4% of the implantees achieved a score of more than 8 in 12 months which was statistically significant. 43.2% in first group and 67.5% in second group achieved a score of less than 8 in 12 months (Table 3). Similar results were obtained by Kameshwaram et al. [30], who concluded that the results of CAP score showed that 10% implantees achieved category 7 in 12 months in 1–5 year age group and 13% achieved category 6 in 12 months; whereas, in 6–10 years age group, 4% achieved category 7 in 12 months and 9% achieved category 6. Govaerts et al. [31] also observed that the CAP score increased after implantation. Using both retrospective longitudinal and cross sectional study designs, Govaerts et al. evaluated data from six age cohorts implanted up to 6 years of age. The CAP scores were rapidly (after 3 months) normalised in children implanted before the age of 2 years. Children implanted later, took longer to achieve scores similar to their normal-hearing peers. A study by Hashemi et al. [27] on 98 children between 2 and 7 years of age revealed a highly significant association between the age at the time of implantation and the auditory performance scores obtained for 12 and 24 months after the operation. Our study, along with aforementioned data provides significant evidence to justify that the age group of 2–3 year is the critical time point to perform a cochlear implantation in a child.

While assessing MAIS score for audiological assessment, we found that preoperative mean score in the 1–4 year age group and 4.1–7 year age group were 2.14 ± 4.57 and 2.57 ± 6.0 respectively. Pre-operative mean score of the second group is more than the first possibly because of long term sound stimulation by the noise in the surroundings, verbal communication by family members and via hearing aids. While in earlier implanted group exposure to stimulation by sound and sound awareness is comparatively for lesser duration. While the post-operative scores in the earlier implanted group supersedes the second, in spite of lesser pre-operative score may be because of the implantation in the critical period and lesser duration of auditory deprivation. In the first group, the postoperative scores at 3, 6 and 12 months were 14.89 ± 7.9, 25.16 ± .8.71, and 37.22 ± 7.05 respectively. In the second group, the postoperative scores were 15.72 ± 8.15, 24.86 ± 7.98 and 33.2 ± 6.24 respectively (Tables 4, 5). The postoperative mean MAIS scores in both the groups were statistically significant at various stages with increasing order according to Friedman test and Wilcoxon Signed Rank test. The MAIS scores when compared in both the groups revealed that the results were comparable but not significant after 3 and 6 months, while they were significant after 12 months (Mann–Whitney Rank Sum Test). In 1–4 year age group 89.1% of the implantees and in 4.1–7 year age group 56% of implantees achieved score of > 35 in 12 months. The results were statistically significant (Table 6). The results of the present study are in line with other studies which show the improvement of the auditory performance. Anderson et al. [32] reviewed data of 37 children who had received cochlear implants before the age of 2 years and were compared to those implanted at a later age. Results showed significant improvement over time (up to 3 years). In a study by Yang in 2004, the auditory performance was measured as 3.93, and 5.86 in 1 and 2 years after the implantation, respectively [33]. Likewise, Donoghue’s in 1998 reported the mean of the auditory performance scores as 4, and 5 in 1, and 2 years after the implantation, respectively [34].

Similarly the SIR scale of O’ Donoghue was utilized to measure the outcome of cochlear implantation with respect to speech, measuring the intelligibility of speech and the quality, which might be recognizable by the listener. The analysis also included the extent to which speech is understood and discriminated by the listener. The results were assessed and categorized accordingly and a score was given taking into account the number of months taken to achieve it. During our assessment the preoperative mean score in the 1–4 year age group and 4.1–7 year age group were 1.03 ± 0.16 and 1.08 ± 0.28 respectively. In first group, the postoperative scores at 3, 6 and 12 months were 1.67 ± .75, 2.48 ± .96, and 4.08 ± .862 respectively. In the second group, scores were 1.7 ± .78, 2.4 ± 1.1 and 3 ± 1.2 respectively (Tables 7, 8). The postoperative mean SIR scores in both the groups were statistically significant at various stages with increasing order according to Friedman test and Wilcoxon Signed Rank test. The SIR scores when compared in both the groups revealed that the results were comparable but not significant after 3 and 6 months while they were significant after 12 months (Mann–Whitney Rank Sum test). In first group 37.8% of the implantees achieved category 5 whereas in second group 5.4% of the implantees achieved category 5 in 12 months which is statistically significant (Table 9). Our study showed that younger implanted group could achieve better speech perception scores. This was also evident in a study by Kameshwaram et al. [30] where, in the 1–5 year age group, 15% achieved category 5 in 12 months and 7% got category 4; whereas in age group 6–10, 8% got both category 4 and 5 in 12 months and 6 months respectively. Similarly the study by Zeitler et al. [35] utilized HINT and CNC scores preoperatively and postoperatively and found highly significant increase in mean and median scores for both tests in each study period. Tobey et al. [36] examined specific spoken language abilities in 160 children and followed prospectively 4, 5, or 6 years after cochlear implantation. Average age at baseline was 16.5 months for the younger group and 42.2 months for the older group and they concluded that earlier implanted children under 2.5 years of age scored higher standard scores. She added that younger ages of implantation are associated with higher levels of performance, while later ages of implantation are associated with higher probabilities of continued language delays. Longitudinal data from this cohort study demonstrated that after 6 years of implant experience, there is a large variability in language outcomes associated with modifiers of rates of language learning that differ as children with implants age. Another study in line with ours is of Dunn et al. [37] who performed a retrospective analysis to determine the effect of age at implantation on speech outcomes. The younger implanted group had higher speech perception scores at 5 years of age, compared to the older implanted group.

Colletti [38] proposed a study to investigate the efficacy of cochlear implants in infants who were implanted at < 11 months of age versus children operated at later age (i.e. 12–36 months) and to document whether children who receive a CI below 11 months of age are able to achieve age appropriate expected spoken language skills, at a follow up time from 4 to 9 years in three groups of children with different ages at implantation (from 4 to 36 months) with a follow up time from 4 to 9 years. The acquired language performances showed that only the scores of the first group overlap the line of normal hearing children, whereas the second and third group never reached the values of normal peers even after 9 years of CI use. The SIR outcomes also favoured no candidate in first two categories, 18% from the third group achieved category 3. All candidates from group 1, 80% of group 2, and 63% of the third group achieved category 5. He demonstrated that very early cochlear implantation (< 11 months) provides normalization of audio-phonologic parameters with no complications.

Data from Kileny et al. implant program clearly demonstrated that children implanted between the ages of 12 and 36 months outperformed children implanted between the ages of 37 and 60 months [39]. This, together with earlier identification of childhood deafness, is pushing the age at implantation lower [40]. For many years, the lower limit for age at implantation was 2 years. In general, using modern techniques, a confident assessment of severe to profound sensorineural hearing loss can be made in a child by the time they are 12 months old.

Early implantation can benefit long term development in two ways. First, it can shorten the interval of deafness with its associated poorer rate of language development, thus reducing the degree to which a child has fallen behind normal hearing peers at the time of implantation. This benefit, therefore, would be reflected in the language status at the time of initial stimulation and represents the intercept in post implantation growth. Secondly, early implantation can provide benefit for language development by altering the rate of development after initial stimulation. Children who were implanted early in childhood had more rapid language growth rates than children implanted later in childhood. In addition, it was found that this relationship had a significant exponential quality such that the relationship between rate of language growth and age at initial stimulation increased as age at initial stimulation decreased. Accordingly, it appears that earlier implantation does provide benefits for expressive language and speech outcomes [41].

The effect of pre-CI hearing aid use and speech therapy also had effect on audiological and speech perception outcomes. Those patients using hearing aid and taking speech therapy had higher preoperative hearing level and some level of oral communication. Niparko and colleagues [42] and Arisi et al. [43] found preoperative hearing levels to be one of several variables affecting CI performance in prelingually deafned children and adolescent’s respectively. Postoperative gain in this group was also better as compared with other patients. In our study, in 1–4 year age group, 15 cases (40.5%) used hearing aid for up to 1 year, 13 cases (35.1%) for 1–2 years, and 3 cases (4.05%) for 2–3 years. While in 4.1–7 year age group, 13 cases (35.1%) used hearing aid for up to 1 year, 13 cases (35.1%) for 1–2 years, 6 cases (16.2%) for 2–3 years. 6 cases in 1–4 year age group and 5 cases in 4.1–7 year age group did not use hearing aid at all. Within the groups Wilcoxon Signed Rank test is used for preoperative and postoperative comparison which showed a significant difference. There is a significant difference among the duration of hearing aid use groups in pre and post op CAP, MAIS and SIR scores. It is observed that within the nil, up to 1 year, 1 to 2 years and 2 to 3 years groups the mean preoperative and postoperative scores are significantly increased. The significance in 2–3 years duration can’t be calculated due to small sample size. Both the groups were compared by Mann–Whitney Rank Sum test which revealed the significance after 1 year of hearing aid use duration attributed to full time implant use, frequent rehabilitation centre attendance and maternal education. After implantation, the scores of both groups increased with increasing time of implant use during the follow-up period, and at each time point, the mean scores of the two groups were comparable. Children in the 1–4 year age group who never used a hearing aid achieved a better CAP score than the later implanted group which used hearing aid for 1–3 years. This phenomenon is also observed in MAIS and SIR scores.

These results indicate that great communication benefits achieved by early implantation without hearing aid use, the results exemplify the importance of enhanced social environments provided by everyday life experience for human brain development and reassure parents considering cochlear implants where hearing aid & speech training is unavailable.

Speech therapy was received in 78.3% of cases of both age groups. In 1–4 year age group 12 cases underwent speech therapy for 1 year, 13 cases for 1–2 years and 4 cases for 2–3 years. In 4.1–7 year age group, 13 cases underwent speech therapy for up to 1 year, 12 had for 1–2 years and 4 for 2–3 years. 8 cases in 1–4 year age group and 8 cases in 4.1–7 year age group did not use Speech therapy at all. Children in the 1–4 year age group who never had speech therapy achieved better scores than the later implanted group who used speech therapy for 1–3 years. Reason attributed to this was the patients were full time users, took frequent participation in the rehabilitation programme and maternal education. This phenomenon is also observed in MAIS and SIR scores. The patients who took speech therapy had some oral communication auditory input preoperatively, so they outperformed other patients and showed maximum benefit from cochlear implant. This is in concordance with the study by Zeitler et al. [35], who reported that patients using oral communication before CI had significantly better objective outcomes than do their peers who used manual or total communication.

Few important challenges were there in this follow up study. One was the need to develop composite measures that were highly reliable and equally representative of communication skills measured at two distinct developmental periods. This study did take into account known confounding factors, but there is the possibility that the differences observed between groups may have been influenced by unknown factors and not just the age at implantation. Furthermore due to ignorance on behalf of parents of the patients, illiteracy, low socioeconomic status, delayed referral results in delayed presentation consequently leading to intervention at an older age group. This is not in accordance to recent studies which show, better results in children less than 12 months. This may be attributed to the fact that all the cases in our study were more than 1 year of age. In addition, some of groups had a small number of subjects, making the power of the analyses less than optimal. A difference may actually exist between groups where this study did not observe a statistically significant difference. Future research should include a larger sample size, as well as attempt to take into account other possible confounding variables. Even after the completion of this study patients are being monitored for long term results of cochlear implantation and audio verbal rehabilitation.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in the study.