Cochlear implant
Neuroprosthesis that restores sound perception via direct auditory nerve stimulation.
A cochlear implant is a device surgically placed inside the body to help people with moderate-to-profound sensorineural hearing loss perceive sound. Instead of relying on the ear’s natural acoustic pathway, it works by sending electrical signals directly to the auditory nerve. With auditory training and therapy, both children and adults can learn to interpret these signals as speech and other sounds, often improving their ability to understand speech in quiet and noisy settings.
The system has two main parts. The external component, called the sound processor, sits behind the ear or, in some designs, as a pebble-shaped unit attached magnetically to the head over the implant site. It contains microphones, digital signal processing chips, a battery, and a coil that sends signals through the skin. Some processors can also be clipped to clothing, which is common for young children. The internal component is the implant itself, which includes a receiving coil, electronics, and an electrode array that is placed inside the cochlea to stimulate the cochlear nerve.
Surgery is done under general anesthesia, usually as an outpatient procedure. Risks are generally low, though some people may experience dizziness, and rarely, tinnitus or bruising of the facial nerve.
Early implants from the 1970s and 1980s offered limited speech perception, but improvements came quickly. Progress has leveled off since modern sound-coding strategies were introduced in the 1990s. By 2019, over 200,000 people in the United States had received a cochlear implant. Many users today achieve reasonable to good hearing and speech understanding, especially when combined with lipreading. However, outcomes vary widely from person to person. Factors that influence this variation include the age at implantation, parental involvement and education level, the duration and cause of hearing loss, how the implant sits in the cochlea, the health of the cochlear nerve, and the individual’s ability to relearn.
The first cochlear implant was invented in 1957 by André Djourno and Charles Eyriès, using a single channel to deliver stimulation. William House created his own version in 1961, and in 1964, Blair Simmons and Robert L. White implanted a single-channel electrode at Stanford University. These early single-channel devices were limited because they could not stimulate different parts of the cochlea at
- inventors
- André Djourno and Charles Eyriès (1957); William House (1961); Graeme Clark and Ingeborg Hochmair with Erwin Hochmair (multi-channel, late 1970s)
- first_implant_year
- 1957
- field
- Neuroprosthetics, otology
- key_components
- External sound processor and internal electrode array
- number_of_recipients_in_US_by_2019
- More than 200,000
Lore & Background
The original cochlear implant was invented in 1957 by André Djourno and Charles Eyriès, using a single-channel design. William House independently invented a cochlear implant in 1961, and Blair Simmons and Robert L. White implanted a single-channel electrode in 1964 at Stanford University. However, single-channel implants were of limited usefulness because they could not stimulate different areas of the cochlea to differentiate frequencies needed for speech detection. In the late 1960s, Robin Michelson and Melvin Bartz constructed a device with biocompatible materials, implanting it in four patients; the results were a watershed for clinically applicable implants. Michelson, Robert Schindler, and Michael Merzenich at UCSF conducted experiments in 1970 and 1971, including implanting a single-channel device in a congenitally deaf woman who demonstrated auditory sensations and pitch perception below 600 Hz but no word recognition. This work was presented at the 1971 American Otological Society meeting but was not well received. NASA engineer Adam Kissiah began designing a cochlear implant in the mid-1970s, using his electronics knowledge, and obtained a patent in 1977 with NASA's help; the commercial product by BIOSTIM Inc. failed to reach the marketplace. The modern multi-channel cochlear implant was independently developed by Graeme Clark in Australia and by Ingeborg Hochmair and Erwin Hochmair in Austria, with the Hochmairs' device first implanted in December 1977 and Clark's in August 1978. The Hochmairs' original 8-channel form did not produce open speech understanding, leading them to change their approach. Clark's multi-channel design, commercialized as the Nucleus device by Cochlear Limited, became the first multi-channel cochlear implant to receive FDA approval in 1985 and the most widely used worldwide.
Reader's Guide
Cochlear implants represent a major advance in treating profound hearing loss, evolving from single-channel devices of limited utility to multi-channel systems that enable speech perception. The surgical procedure is performed under general anesthesia, typically as outpatient surgery, with minimal risks though occasional dizziness, tinnitus, or facial nerve bruising. The implant has two main components: an external sound processor (worn behind the ear or as a pebble-shaped unit) and an internal electrode array placed in the cochlea. Speech perception improved greatly from the 1970s and 1980s but plateaued after modern sound coding strategies in the 1990s. By 2019, over 200,000 people in the United States had received a CI. Many users gain reasonable to good hearing and speech perception, especially with lipreading, but outcomes vary widely due to factors like age at implantation, duration and cause of hearing loss, implant placement, cochlear nerve health, and individual relearning capabilities. Totally implantable cochlear implants (TICIs) are in development, incorporating all external components internally, with initial trials showing safety and comparable performance, though challenges with microphone sensitivity remain. Most modern CIs can be used with assistive listening devices (ALDs) that stream sound directly from Bluetooth devices, improving hearing in challenging situations.
Did You Know?
- The original cochlear implant was invented in 1957 by André Djourno and Charles Eyriès using a single-channel design.
- NASA engineer Adam Kissiah designed a cochlear implant during his lunch breaks and evenings at the Kennedy Space Center technical library, obtaining a patent in 1977.
- The modern multi-channel cochlear implant was independently developed by Graeme Clark in Australia and by Ingeborg Hochmair and Erwin Hochmair in Austria, with first implantations in December 1977 and August 1978 respect
- More than 200,000 people in the United States had received a cochlear implant through 2019.
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