Objective: While investigators have reported that patients with GJB2-associated deafness and cochlear implants have preferable language development, the mechanisms of this phenomenon remains unknown. The goal of the present study was to assess higher brain functions of patients with GJB2-related and GJB2-unrelated deafness as a method of evaluating language development.
Methods: Eight children with cochlear implants were subjected to genetic testing for GJB2 and underwent the Raven colored progressive matrices test, Rey's auditory verbal learning test, Rey's complex figure test, the standardized language test for aphasia, the picture vocabulary test, and the standardized comprehension test for abstract words.
Results: Three children were diagnosed with GJB2-related deafness, and five children were diagnosed with GJB2-unrelated deafness. All three GJB2-related cases demonstrated normal range higher brain functions and fair language development. By contrast, one GJB2-unrelated case showed a semantic disorder, another demonstrated a visual cognitive disorder with dyslexia, and another had attention deficit-hyperactivity disorder.
Conclusions: Children with GJB2-unrelated deafness showed a high frequency of heterogeneous disorders that can affect proper language development. This difference between children with GJB2-related and GJB2-unrelated deafness may account for the improved language development in children with GJB2-related deafness and cochlear implants. Further, genetic diagnosis of the non-syndromic hearing loss represents a useful tool for the preoperative prediction of outcomes following a cochlear implant procedure.