Auditory Brainstem Implant in Prelingually Deaf Children

Introduction: Auditory brainstem implant (ABI) has been placed in children who are born deaf due to cochlear nerve aplasia or with a severe degree of inner ear dysplasia, and for whom a cochlear implant is not an option. Application of ABI is more complicated than cochlear implant because ABI electrodes are placed in the cochlear nucleus, which is near some important cranial nerves. Electrical stimulation of the cochlear nucleus has some risks. When fitting the ABI, it is also important to decide which electrodes have effective auditory stimulation and which electrodes have side effects and must be closed. In children with cochlear nerve aplasia or inner ear dysplasia, there are risks and limitations because of the size and shape of the cochlear nucleus. We do not have information on the effects of long-term electrical stimulation of the cochlear nucleus in children.

Material and Methods: Auditory brainstem implants were placed in 14 children (2–5 years old) with cochlear nerve aplasia and cochlear malformations. Thirteen Nucleus ABI-24 devices and 1 MED-EL PULSAR CI 100 ABI were used. Intraoperative EABR measurements were done in all children. Initial stimulation was carried out 6–8 weeks after the implantation. The electrodes that caused side effects and nonauditory sensations were closed. Language and auditory development of children were evaluated every 3 months.

Results and Discussion: The children with implanted ABIs were followed up every 2 weeks during the first 3 months and every 3 months after that. Intraoperative EABR measurements yielded important tips for fitting. Fitting parameters and stimulation parameters were observed, and some needed changes were identified. The numbers of open electrodes were increased, and some electrodes that had nonauditory sensations were found to have auditory sensation. The numbers of electrodes that had side effects were decreased during follow-up. The results of ABIs in prelingual children showed improved auditory plasticity and language development, and changing some fitting parameters caused further improvement. Auditory sensations in lateral electrodes were thought to be the result of growth of the cochlear nucleus after the stimulation. Improvement in language and auditory developments were found in all children. The first 2 children have the ability of aural communication after 2.5 years of rehabilitation. We believe that careful surgery, intraoperative EABR measurements, proper fitting, and rehabilitation will increase the benefits of ABI applications in children.