Assessment of vocabulary development in children after cochlear implantation.

Objectives: To assess vocabulary development in children following cochlear implantation and to evaluate the effect of age at implantation on performance.

Design: Retrospective study (mean follow-up, 3(1/2) years).

Setting: Tertiary center.

Patients: Children with prelingual deafness provided with a cochlear implant between 1988 and 1999, who serially performed the Peabody Picture Vocabulary Test-Revised (60 patients) and the Expressive One-Word Picture Vocabulary Test-Revised (52 patients). The children were subgrouped into those receiving implants at younger than 5 years and at 5 years or older.

Outcome Measures: Age-equivalent vocabulary test score and gap index (chronological age minus the age-equivalent score, divided by the chronological age at the time of testing) were calculated. For each test, the following were performed: calculation of rate of change for age-equivalent score; comparison of earliest and latest gap indices means (the cohort and intergroup and intragroup comparison); and multiple regression analysis demonstrating the effect of age at implantation, sex, communication mode, etiology of deafness, and residual hearing on the rate of vocabulary development.

Results: Expressive and receptive vocabulary development rates were 0.93 and 0.71 (age-equivalent scores per year), respectively. Subgrouped by age at implantation, the children's rates (for both vocabularies) were not statistically different (Peabody Picture Vocabulary Test-Revised, P =.90; Expressive One-Word Picture Vocabulary Test-Revised, P =.23). The global latest gap indices were significantly less than the earliest (Peabody Picture Vocabulary Test-Revised, P =.048; Expressive One-Word Picture Vocabulary Test-Revised, P<.001), indicating an improvement in age-appropriate vocabulary development over time. The age subgroups demonstrated similar results, except for the younger group's receptive gap index. On multiple regression analysis, the significant predictive variables were residual hearing (Expressive One-Word Picture Vocabulary Test-Revised) and male sex and oral communication mode (Peabody Picture Vocabulary Test-Revised).

Conclusions: Children with cochlear implants developed their vocabularies at rates that were sufficient to prevent an increase in their gap indices as related to ideal scores at testing. A late age at implantation does not singularly preclude beneficial development of vocabulary.