Final answer:
An abnormal auditory nerve would prevent a cochlear implant from effectively restoring hearing since the device relies on the ability to stimulate this nerve directly.
Step-by-step explanation:
The type of hearing loss that would not be restored by a cochlear implant is hearing loss resulting from an abnormal auditory nerve.
Cochlear implants work by bypassing damaged portions of the ear and directly stimulating the auditory nerve, but if the auditory nerve itself is abnormal, the electrical impulses sent by the implant will not be able to reach the brain effectively.
Options such as hearing loss due to absence or loss of hair cells in the organ of Corti, fracture of the cochlea, and damage to bones of the middle ear could potentially be overcome with a cochlear implant.
These conditions affect structures that the implant is designed to bypass, so the direct stimulation to the auditory nerve would still be possible as long as the auditory nerve is functional.