Prevalence of various etiologies of hearing loss among cochlear implant recipients: Systematic review and meta-analysis

Objective: To investigate the etiology of deafness in cochlear implanted children and to address the question whether there is a need for more thorough diagnostics, especially concerning genetics. Design: Systematic review. Four databases were searched for studies (year 2000–2014) on cochlear implanted children (n > 100). Studies were excluded if etiology had influenced their inclusion criteria. Eligibility and methodological quality were assessed independently by three authors. The studies’ description of diagnostic evaluation was categorized in three groups. Study sample: Sixteen studies were included (5069 children). Results: The most common etiological categories were ‘Unknown’ 40.3% (95% CI 32.8 to 48.0), ‘Non-syndromic’ 22.4% (95% CI 17.1 to 28.2), and ‘Postnatal’ 11.3% (95% CI 7.2 to 16.2). Studies published after 2006 had a lower proportion of ‘Unknown’ etiology 35.3% (95% CI 28.0 to 42.8) than older 45.5% (95% CI 31.0 to 60.4). Important information was missing from several studies: 11 (69%) studies did not provide detailed description on diagnostic evaluation of the etiology of deafness and had a higher proportion of ‘Unknown’ etiology. Conclusions: In order to ensure a higher level of comparability in future studies, we recommend agreement upon an international standard of diagnostics and the introduction of an international standard for reporting etiology.