Born Without an Auditory Nerve: Auditory Brainstem Implant to the Rescue
Babies born deaf are typically referred for a cochlear implant (CI), an auditory prosthetic device that is surgically implanted in the inner ear. Many children with the CI learn to understand speech without visual cues, acquire spoken language, and are mainstreamed into regular classrooms. Despite the general success of the CI in children, a small proportion of this population is not eligible for the CI because of a deficient auditory nerve or other anatomical deformities. By necessity, such children become reliant on sign language as their primary means to communicate and are typically placed in special school programs for deaf children. Now, another type of implantable auditory device, the auditory brainstem implant (ABI), is undergoing FDA clinical trials to bring hearing to these children. The ABI is similar to the CI but bypasses the cochlea and is placed directly on the cochlear nucleus of the brainstem. The ABI delivers a more scrambled pattern of information to auditory cortex than does the CI, and this pattern is highly degraded and distorted compared to normal hearing. Yet there is emerging evidence that the plasticity of the developing auditory cortex is sufficient so that young deaf children can decipher this scrambled signal and learn to understand speech and language. The focus of this presentation is to discuss emerging communication outcomes in pediatric ABI recipients. Notably, the children enrolled in the pediatric ABI clinical trial are being assessed on the same battery of speech perception tests that is used in a national, multicenter study on pediatric cochlear implantation. Use of this battery allows us to compare auditory development between pediatric CI and ABI users. Data from our center and those from other investigators are showing that auditory development in well-selected children appears to follow a similar trajectory to that of children with CIs. These early data suggest that the child’s brain is able to unscramble the ABI signal in a way that enables the acquisition of spoken language.