Effectiveness Of Prelingually Deaf Children Following Cochlear Implantation Systematic Review

Objective To assess the clinical effectiveness of prelingually deaf children following cochlear implantation at different implantation ages.Methods MEDLINE( 1984-2006.7 ), EMBASE(1984-2006.7), Cochrane Library (Issue 2,2006 ) ,CBMDisk (1984-2006.7 ) and CNKI (1984-2006.7) have been searched. Only English and Chinese literatures have been searched. Non-randomized clinical studies about that during follow-up times, speech perceptions were regularly tested for the prelingually deaf children following cochlear implantation at different ages have been included. Two authors( Hu Ruidan, Zheng Hong independently assessed the methodological quality of studies and extracted data and checked one another. Disagreement was resolved by discussion or the third person (Li Jing). Revman 4.2 had been used for Meta-analysis.Results There were 5 non-randomized control studies including 497 profound to severe sensorinural prelinguistically deafened children met our inclusion criteria. And results of 256 children were involved in Meta-analysis. All trials were of lower methodological quality.Comparing PTA: 1 study demonstrated that there were no significant differences among pre-implantation PTA thresholds in the studied frequencies (0.5-4 kHz) in different age groups of prelinguistically deafened children, but postoperatively the PTA thresholds were significantly improved in all groups of children, and a clear improvement in sound detection of frequencies in the speech spectrum at conversational levels showed. Postoperatively, mean PTA thresholds ranged from 32 to 44 dB HL, and did not significantly change up to the eighth year of follow-up.Comparing speech perception of prelingually deaf children following cochlear implantation below 3 years old and 3-6 years old, (1) 12 months after operation: 4 studies including 256 subjects (below 3y-group, 160 subjects; 3-6y-group, 96 subjects) reporting speech perception scores at this time. Meta analysis of 2 studies including 56 subjects (below 3y-group, 31 subjects; 3-6y-group, 25 subjects ) showed that children implanted below 3 years of age performed significantly better than children implanted at 3-6 years. 1 study including 130 subjects (below 3y-group, 94 subjects; 3-6y-group, 36 subjects) demonstrated that children implanted below 3 years of age performed significantly better than children implanted at 3-6 years. While another study including 70 subjects (below 3y-group, 35 subjects; 3-6y-group, 35 subjects) demonstrated that there was difference between children implanted below 3 years of age and children implanted at 3-6 years, but there was no significant difference. (2) 24 months after operation: 3 studies including 233 subjects (below 3y-group, 130 subjects; 3-6y-group, 87 subjects) reporting speech perception scores at this time. Meta analysis of 2 studies including 103 subjects (below 3y-group, 52 subjects; 3-6y-group, 51 subjects) showed that there was difference between children implanted below 3 years of age and children implanted at 3-6 years, but there was no significant difference. Only one study including 130 subjects (below 3y-group, 94 subjects; 3-6y-group, 36 subjects) demonstrated that children implanted below 3 years of age performed significantly better than children implanted at 3-6 years. (3) 36 months after operation: 2 studies including 163 subjects (below 3y-group, 111 subjects; 3-6y-group, 52 subjects) reporting speech perception scores at this time. 1 study including 130 subjects (below 3y-group, 94 subjects ; 3-6y-group, 36 subjects) demonstrated that children implanted below 3 years of age performed significantly better than children implanted at 3-6 years. Another study including 33 subjects (below 3y-group, 17 subjects; 3-6y-group, 16 subjects) demonstrated that there was difference between children implanted below 3 years of age and children implanted at 3-6 years, but there was no significant difference.Comparing speech perception of prelingually deaf children following cochlear implantation below or above 6 years old, 2 studies including 322 subjects (below 6y-group, 200 subjects; above 6y-group, 122 subjects) demonstrated that children implanted below 6 years of age performed better than children implanted above that age, the differences showed 1 or 2 years postoperatively.Conclusion Prelinguistically deafened children implanted below 3 years of age performed significantly better than children implanted at 3-6 years on speech perception, regardless of follow-up times, 12 months,24 months and 36 months after operation.More well-designed trials as well as standard speech perception tests need to be conducted to identify the influence of surgery age on speech perception ability.