Outcomes with cochlear implants vary, depending on a number of factors, including the Length of time between onset of hearing loss and placement of the implant (shorter duration leads to better outcomes) Cause of the underlying hearing loss Position of the implant within the cochlea Brain stem implants Although cochlear implants are not an option for patients who have had both acoustic nerves destroyed (eg, by bilateral temporal bone fractures or neurofibromatosis) or are born without cochlear nerves, these patients can have some hearing restored by means of brain stem implants that have electrodes connected to sound-detecting and sound-processing devices similar to those used for cochlear implants, although usually not as good.