[Linguistic skills and its influencing factors of cochlear implanted children with cochlear nerve aplasia diagnosed by MRI].

Objectives

This study aimed to evaluate the expressive vocabulary ability and sentence complexity in cochlear implanted children diagnosed with cochlear nerve aplasia (CN-A), and to analyze potential influencing factors.

Methods

This cross-sectional study included 35 children diagnosed with CN-A by MRI, with a mean age of cochlear implantation of 22.1 (SD: 8.0) months. Twelve were bilaterally implanted (bilateral CI group), 13 were unilateral implanted with hearing aids on the contralateral ear (bimodal group), and the others were unilaterally implanted (unilateral CI group). After at least 36 months of device use following initial activation, the quantity of expressive vocabulary was assessed using the Early Vocabulary Inventory for Mandarin Chinese (EVI). The mean length of the three longest utterances (M3L) and the sentence complexity were assessed using the Mandarin Communicative Development Inventory for infants and toddlers. Auditory and speech perception outcomes were also evaluated, including the Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR), and a speech recognition test. Preoperative aided hearing threshold average (aided-PTA) and the diameter of the auditory nerve to the facial nerve ratio at the cerebellopontine angle (AN/FN ratio) in MRI were retrospectively analyzed. The effect of implantation age, cochlear usage duration, preoperative PTA, AN/FN ratio, and prosthetic configuration (unilateral CI/bilateral CIs/bimodal) on expressive vocabulary and grammatical abilities was analyzed.

Results

The average number of expressive vocabularies was 273.7 (SD: 220.1), the mean M3L was 4.8 (SD: 1.4), and the average sentence complexity score was 27.3 (SD: 14.1) in children with CN-A. There were significant positive correlations between expressive vocabulary and M3L (r=0.59, P=0.001), as well as sentence complexity (r=0.91, P<0.001). The quantity of expressive vocabulary, M3L, and sentence complexity were significantly positively correlated with categories of auditory performance (CAP) and speech intelligibility rating (SIR) scores (P<0.01). There were no significant correlations between implantation age, duration with CI, and expressive vocabulary size, M3L and sentence complexity (P>0.05). Multi-linear regression analysis showed that the AN/FN ratio, per-operation aided-PTA and prosthetic configuration were significant predictors for the vocabulary size (P>0.05). Bimodal children had higher expressive vocabulary size than bilateral CIs and unilateral CI children, with significant differences between bimodal and unilateral CI children (P<0.01).

Conclusions

The linguistic skills in children with CN-A are severely impaired. Vocabulary ability is significantly correlated with sentence construction and grammatical ability. The relative auditory nerve diameter on MRI, per-operation hearing level and prosthetic configuration are important factors in predicting the vocabulary development of children with CN-A.