Cochlear Implants

Bypassing damaged hair cells with direct nerve stimulation

Overview

A cochlear implant is a surgically implanted device that provides a sense of sound to people with severe to profound sensorineural hearing loss who gain limited benefit from hearing aids. An external processor captures sound, converts it into a coded signal, and transmits it across the skin to an internal receiver, which drives an electrode array inserted into the cochlea to stimulate the auditory nerve directly, bypassing damaged hair cells. Early single channel devices were developed by William House in the 1960s and 1970s, and Graeme Clark in Australia led development of the multichannel implant, first implanted in 1978. Candidacy criteria have broadened over time and now include many adults and children, and in some countries single sided deafness. The device is typically activated a few weeks after surgery, and initial sound is often described as artificial before the brain adapts over months. Outcomes depend on factors such as the duration of deafness and age at implantation, and children implanted early often develop spoken language.