Biological Mechanism of Cochlear Implant Technology in Humans
The World Health Organization reports that hearing loss was the most common form of sensory impairment in humans, affecting 360 million persons worldwide, with a prevalence of 183 million adult males and 145 million adult females. The most common source of hearing loss is sensorineural hearing loss, characterized by disfunctions of the sensory organ: the cochlea and its associated structures. These dysfunctions may be genetic or acquired. In the latter case, it can be due to environmental factors such as chemical agents or noise exposure, or to age related senescence. In patients with sensorineural hearing loss, the functions of the cochlear cells and tissues are lost. Nevertheless, some auditory neurons survive, and the role of the cochlear implants is to stimulate them directly by shunting the cochlea. In this case, the hearing of patients with profound hearing loss can be successfully rehabilitated with cochlear implants capable of encoding and delivering the spectral and the temporal information of sound to the surviving auditory neurons. In this review, we summarize the physiological mechanisms involved in hearing loss and hair cell apoptosis, the role of cochlear implants in cochlear neuron stimulation, and the clinical advantages and disadvantages related to this cochlear device implantation.