A cochlear implant is an electronic device in which an extracorporeal speech processor converts sound into a certain coded form of electrical signal and restores or reconstructs the hearing function of a deaf person by directly exciting the auditory nerve through an electrode system implanted in the body. In recent years, with the development of electronics, computer technology, phonetics, electrophysiology, materials science, and ear microsurgery, cochlear implants have moved from experimental research to clinical application. Cochlear implants are now used worldwide as a routine treatment for severe to total deafness. A cochlear implant is an electronic device in which an external speech processor converts sound into a certain coded form of electrical signal, and restores, improves, and rebuilds the hearing function of a deaf person by directly exciting the auditory nerve through a system of electrodes implanted in the body. In the past two decades, with the development of high technology, cochlear implants have progressed rapidly from experimental research to clinical application. Cochlear implants are now used worldwide as a routine treatment for severe to total deafness. The cochlear implant is currently the most successfully used biomedical engineering device. The history of cochlear implants dates back to the 1800’s when Volta in Italy discovered that electrical stimulation of the normal ear could produce hearing, and 1957 when Djourno and Eyries in France first implanted electrodes into the cochlea of a totally deaf patient, allowing the patient to perceive ambient sounds and gain a sense of sound, and in the 1960’s and 70’s when scientists in Europe and the United States successfully restored hearing to deaf patients through electrical stimulation. Studies in human and animal models revealed characteristics of the hearing evoked by electrical stimulation and problems that needed to be solved. Such as: narrow dynamic range, steep loudness growth and poor recognition of timely threshold tones, etc. In 1972 the American House-3M single-channel cochlear implant became the first generation of commercialized devices. The Nucleus 22 cochlear implant was approved by the FDA in Australia in 1982 and became the first multichannel cochlear implant device used worldwide. Today the world’s major cochlear companies are Cochlear (Australia), Medel (Austria) and AB (USA). By early 2010, more than 100,000 deaf people around the world had used cochlear implants, more than half of whom were children. Multi-channel cochlear implantation began in China in 1995, and the technology has become more mature. With the increase in the number of cochlear implant cases and the expansion of the range of indications, the efficacy and safety of cochlear implantation in deafness cases with some special indications have been confirmed, further expanding the indications for cochlear implantation. For example: cochlear implantation in patients with no residual preoperative hearing; cochlear implantation in cases of inner ear malformation and cochlear ossification; cochlear implantation in patients with combined chronic otitis media; cochlear implantation in patients with younger deafness; cochlear implantation in patients with advanced deafness. Human beings need not only normal hearing to acquire normal language, but also normal development of the auditory language center, which is why adult prespeech deaf patients can hear sounds but cannot understand language and speech, even with cochlear implants. Studies have shown that the human auditory language center is fully developed by the age of 5. In adults with prelingual deafness, deafness occurs before the development of language and the opportunity for normal development of the auditory language center is lost. The optimal age of implantation for prelingually deaf patients is before the age of 5. In adults with postlingual deafness, the cause of their deafness may be sudden deafness, drug-induced deafness, or acquired deafness based on congenital inner ear malformations (large vestibular conduction canal syndrome). These adult deaf patients are called adult postlingual deaf patients because they used to have normal hearing and acquired normal speech with adequate development of their auditory speech centers prior to their deafness. Adult postlingually deaf patients are one of the best indications for cochlear implants. These deaf patients have normal development of their auditory language centers prior to their deafness, and after receiving a cochlear implant, they regain their hearing and are able to recall their past memory of language, so these patients can regain their language skills in a relatively short period of time. An important issue for adults with postlingual deafness is that early cochlear implantation after deafness will quickly recall their past memory of language and obtain better language results. If the deafness is prolonged, the patient’s memory of past language will fade, leading to a decrease in the effectiveness of the cochlear implant. There is a growing concern about cochlear implants for elderly deaf patients. The majority of elderly deaf patients are postlingually deaf, and the cause of their deafness, in addition to the reasons mentioned above, is more often due to progressive hearing loss in old age until the use of hearing aids is ineffective. With the development of social economy and the increase of life expectancy of the population, the quality of life of the elderly has been more concerned by the society and families. Restoring the auditory speech ability of the elderly can enhance their speech communication ability, improve their psychological state, make them gain self-confidence and greatly improve their quality of life. Elderly deaf patients who receive cochlear implants can achieve excellent hearing and speech results. For example, at the Cochlear Implant Center at the University of Iowa Hospital, a significant number of cochlear implant recipients are elderly deaf patients, and the ability of these elderly cochlear implant recipients to care for themselves and communicate is greatly improved. For example, before the cochlear implant, they were afraid to drive, but after receiving the cochlear implant, they can drive to the supermarket, hospital, etc.