How a Cochlear Implant Enables You to Hear
A cochlear implant has both internal and external components:
The external component consists of a sound processor in the form of either a behind-the-ear (BTE) or box-shaped device. This device is connected by a cable to a headpiece that rests on the scalp above the ear. The sound processor is sometimes called a speech processor.
The internal component consists of the actual “cochlear implant”, which nests within the mastoid bone.
Thus, you can see that a cochlear implant bypasses the damaged or missing cilia and directly stimulates the auditory nerve, enabling the implant user to hear sound.
Hearing aids, by contrast, depend on whatever cilia are present and capable of being stimulated. If there are no cilia, or if they all are damaged, the auditory nerve cannot be stimulated. In this event no hearing aid will enable an individual to hear. The person can then consider the option of a cochlear implant.(NVRC wishes to thank author Mardie Younglof for this summary)
Additional Resources on Cochlear Implants