Cochlear implant – speech and language development in deaf and hard of hearing children following implantation

Bacground/Aim. Almost 200 cochlear implantations were done in the four centers (two in Belgrade, per one in Novi Sad and Niš) in Serbia from 2002 to 2009. Less than 10% of implantees were postlingually deaf adults. The vast majority, i.e. 90% were preand perilingually profoundly deaf children. The aim of this study was to assess the influence of improved auditory perception due to cochlear implantation on comprehension of abstract words in children as compared with hearing impaired children with conventional hearing aids and normal hearing children. Methods. Thirty children were enrolled in this study: 20 hearing impaired and 10 normal hearing. The vocabulary test was used. Results. The overall results for the whole test (100 words) showed a significant difference in favor of the normal hearing as compared with hearing impaired children. The normal hearing children successfully described or defined 77.93% of a total of 100 words. Success rate for the cochlear implanted children was 26.87% and for the hearing impaired children with conventional hearing aids 20.32%. Conclusion. Testing for abstract words showed a statistically significant difference between the cochlear implanted and the hearing impaired children with hearing aids (MannWhitney U-test, p = 0.019) implying considerable advantage of cochlear implants over hearing aids regarding successful speech development in prelingually deaf children.


Introduction
More than 200 cochlear implantations were performed from 2002 to 2009 in Serbia (four cochlear implant centers -Clinical Center of Serbia and Clinical Hospital Center "Zvezdara" in Belgrade, Clinical Center of Vojvodina in Novi Sad and Clinical Center Niš).Less than 10% of patients were postlingually deaf adults while more than 90% were children with prelingual, perilingual or early postlingual deafness.Auditory deprivation and lacking of speech stimuli Ostojić S, et al.Vojnosanit Pregl 2011; 68(4): 349-352.leads to severe consequences in speech and language development.If early intervention during "critical period" for speech development is missed stigma of the deaf will remain permanently and a person will be handicapped [1][2][3] .Stigma of the deaf is characterized by poor speech comprehension and language communication.Cochlear implantation tends to improve auditory perception in severely to profoundly deaf children.Auditory skills of hearing impaired children are specific and variable due to different etiologic factors 4 .Listening progress improves communication capacity and overall quality of life of hearing impaired children.Numerous studies have shown considerable progress following cochlear implantation 5 .Communication skills could be severely affected by poor speech perception in case of prelingual or perilingual hearing loss 6,7 .Studies regarding short-term auditory memory for short words have shown a rapid increase in cochlear implanted children shortly after the implantation 8 .Auditory perception is not the only variable inducing speech and language development [7][8][9] .A whole lot of factors such as intelligence, rehabilitation, education, social and psychological issues could affect speech and language of hearing impaired children.Severe to profound deafness affects not only listening and speech but changes the whole deaf personality 10 .
The aim of the study was to assess the impact of improved auditory perception on speech and language development in cochlear implanted children.Abstract words are hard to understand and acquire for severely to profoundly deaf children.Therefore, we decided to evaluate communication outcome in deaf children with cochlear implants and hearing aids in comparison with their hearing peers.

Methods
The overall sample in the study consisted of 30 children aged 4 to 7 years, divided into three groups: E1 -10 deaf children with cochlear implants, E2 -10 deaf children with hearing aids and C -10 hearing children of the same age.All of the deaf children in this study had a severe to profound congenital hearing loss.They were enrolled in speech and hearing rehabilitation in Audiology Rehabiltation Department of Institute for ENT&HNS of Clinical Center of Serbia, Belgrade.
There is a lack of valid instruments for speech and language evaluation in children."Vocabulary test" 1 is an instrument for language evaluation in children aged 3-7 years.It has 100 items divided into five groups of 20 words each, according to age, for 3-, 4-, 5-, 6-and 7-year old children.The test for 3-year-old children has 9 common and 1 abstract word.The number of abstract words gradually rises so that the test for 7-year-old children consists of 5 common and 15 abstract words.It represents vocabulary and understanding abstract words, such as death, life, punishment, satisfaction, etc.The test results were evaluated as follows: absent (0), recognizes the word (1), describes the word (2) and defines the word (3).
The data were statistically analysed and displayed in tables and graphs.Mann-Whitney-U-test for small independent samples was used.

Results
Table 1 shows overall results of the vocabulary test for all three groups.The hearing children had much better achievements than hearing impaired children in both E1 and E2 groups.We would like to point out superior results of cochlear implanted children as compared to children with hearing aids.
Table 2 shows the list of the least recognized words for all three groups.The hearing children did not recognize the word purpose, except one kid.The list of the abstract words that were not recognized by cochlear implanted children consisted of 25 items, whereas the list of words that the children with hearing aids did not recogize was consderably longer (36 items).Table 3 shows a comparison of the overall results for all three groups of the children.The overall achievement of cochlear implanted children (E1) was superior to the results of the children with hearing aids (E2) but the difference was not statistically significant.
Table 4 shows a comparison of the results for abstract words for all tree groups.Ability to describe and define abstract words was highest in rehabilitation of congenitally deaf children.The superior achievement of the children with cochlear implants regarding abstract words understanding is clearly emphasized in Table 4.

Discussion
Analysis of the results revealed that regarding abstract words all of the children achieved best results for words mother, love and friendship.All of them found those words familiar and easy to define.Quantitative analysis showed that the deaf kids had a limited vocabulary and poor grammar, but nevertheless they understood the meaning (example, from the group E1-S.P. "Mother -mom is mine, loves you, gives milk" and from the control group of hearing kids -N.M. "Mother -everyone has got a mother, that is the most important...").
The hearing children from the control group described all of the words, yet they did not reach the maximal score of 141 (3 points for each word), but only 97 (69%).Among 47 abstract words the word purpose was the least recognized.Only one kid described it and got 3 points.
The hearing children were superior to both experimental groups with cochlear implant (E1) and hearing aids (E2), in defining both common and abstract words.Such results were expected.Congenital or early acquired prelingual hearing loss interferes with speech and language development affecting phonological, semantic and every other aspect of speech 11 .Early intervention with hearing aids or cochlear implant could reduce the consequences of deprivation but never fully eliminate them so that backlog compared to the hearing peers is always obvious.
The difference in overall achievement for both children with cochlear implants and hearing aids is not statistically significant (Table 3).
It complies with findings of other authors that the deaf child development is influenced by multiple factors 7,12 .Regardless of the type and quality of amplification some kids are better comunicators than others.All of the children in both experimental groups (E1 and E2) were enrolled in continuos speech and hearing rehabilitation, so that their vocabulary was fairly developed and they were capable of solving these tasks.When it comes to abstract words there is a significant difference in hearing in cochlear implanted over children with hearing aids (Table 4).Cochlear implanted children were so far superior to deaf children with hearing aids regading speech perception.They have much better auditory skills (detection, discriminaton, identification and comprehenssion) and they perform better on the Ling 6-sound test, phonemes, logatomes, short words, polysyllables, sentences 7 .Congenitally deaf children develop speech perception and consistency in the first three years following cochlear implantation.Children implanted before the age of 2 years could reach their hearing peers by the age of 6, if they are subjected to intensive speech and hearing rehabilitation [13][14][15] .Comparison of the results in this study with other authors findings was not possible, because of language differences.There are no available studies in Serbian language or similar languages like Croatian or Bosnian.Complete results for 100 words showed significant difference between hearing and deaf children (Tables 1  and 3).The overall success rate was 77.93% for the hearing children (C), 26.87% for the cochlear implanted (E1) and 20.32% for the deaf children with hearing aids (E2) (Table 1).The difference for abstract words was statisticlly significant (Mann-Whitney U-test, p = 0.019) between the groups E1 and E2 which suggest that cochlear implant significantly contributes to speech development in profoundly deaf children.

Conclusion
Cohlear implantation has statistically significant impact on speech and improves auditory skills and language development in the deaf children.There is an abstract words acquisition, with no statistically significant difference in vocabulary of the cochlear implanted and the deaf children with hearing aids, although the cochlear implanted children show better overal scores of the described and defined words.

Table 1 Overall results of the vocabulary test
C -hearing children; E1 -cochlear implanted children; E2 -children with hearing aids; AS -average score; (+) -best score in the group; (-) -worst score in the group

Table 3 Comparison of overall results
C -