An ABI is similar to a cochlear implant, except the electrodes are implanted directly in the base of the brain. ABIs are used when a person has NF type 2 (neurofibromatosis type 2) and have to have their auditory nerves cut (which renders them useless as far as cochlear implants are concerned). People with ABIs generally only hear environmental sounds–not clear speech. ABI technology is today where CI technology was 25 years ago.
Auditory Brainstem Implant (ABI)