The purpose of this study is to evaluate the clinical safety and efficacy of the Nucleus™ 24 Auditory Brainstem Implant (ABI) in pediatric patients who do not have Neurofibromatosis Type 2 (NF2); specifically, children with total hearing loss due to severe cochlear anomalies, cochlear nerve disorders or failed cochlear implantation. These conditions can include: developmental or acquired cochlear nerve deficiency (CND), cochlear aplasia, post-meningitis cochlear ossification, or cochlear malformation. This study proposes to implant up to 10 pre-linguistic young children (18 mos to 5 yrs. of age) and up to 10 post-linguistic children (<21 yrs of age) with the Nucleus 24 Multichannel ABI in an attempt to demonstrate safety of the surgical procedure and device stimulation and the potential for auditory benefit beyond that experienced with a CI. These children would not qualify for the Nucleus ABI device, as their etiology is not an approved indication such as neurofibromatosis Type 2(NF2). Further, these children do not benefit from conventional hearing aids or cochlear implants.