ABSTRACT
Despite the many unanswered questions of cochlear physiology, it is clear that, despite the small neural distributions of the outer hair cells, they are extremely important to hearing. They are also very fragile. Damage to the auditory system usually is first seen as outer hair cell injury, with noise and direct head trauma typically destroying the outer row of outer hair cells first. Interestingly, many ototoxic drugs tend to injure the inner row of outer hair cells. The maximum hearing loss (threshold shift) that occurs when the outer hair cells are lost is ---50 dB. The hearing loss exceeds 60 dB only when the inner hair cells also become damaged. When all the hair cells are lost, no stimuli are available to excite the nerve endings, and consequently there is no sensation of hearing, although the nerve itself may be entirely intact. Considerably more research is necessary to clarify the functions of even the hair cells, let alone the entire auditory system. The reader is encouraged to consult an excellent summary by Dallos for a review of other concepts in cochlear physiology, as well as other sources (6).
