Cochlear implantation is a surgical treatment for people with severe-to-profound hearing loss caused by permanent inner-ear damage. It does not completely restore hearing, but it can dramatically improve it.
The cochlea is a snail-shaped bony space filled with fluid. It sits at the inside end of the ear canal, encased in the skull bone. When sound vibrations reach the inner ear, they move the fluid inside the cochlea. Tiny hairs in the cochlear fluid then move and transmit electrical signals to the auditory nerve. However, when these hairs become damaged, the sound vibrations do not get transformed into nerve signals, and the patient experiences hearing loss. (Loud noise, drugs, viruses, family inheritance, trauma, and Meniere’s disease can all damage cochlear hairs.) A cochlear implant bypasses the damaged cochlea and delivers its own electrical signals directly to the auditory nerve.
The surgeon places the implant inside the skull behind the ear. Wires from the implant are placed near the auditory nerve, bypassing the damaged cochlea. To pick up sounds from the environment, the patient wears a device behind the ear (which looks similar to a hearing aid) consisting of a microphone, a processing device to filter the signal, and a transmitter. The transmitter sends its information through the skull to the implant device via an FM signal.
The surgery lasts about two hours and usually requires general anesthesia. The patient will stay overnight in the hospital. Usual daily activities may be resumed after two to three days. The patient will have sutures removed seven to 10 days after surgery. Most patients can return to work and resume full activities after the sutures are removed.
The patient takes oral medication for pain and antibiotics to prevent infection. Discomfort is usually minimal.
Cochlear implantation is a surgical procedure and should be undertaken only if conventional hearing aids do not work adequately. For adults, this usually means that the patient understands no more than half of the words spoken to him while wearing a hearing aid. Implantation may require months of follow-up therapy to help the recipient interpret the sounds he hears through the device. For this reason, implantation is most successful in adults who have recently lost their hearing (because they can use the implant’s signals to “remember” sounds) and in young children (because they adapt to the device more readily). Patients must also be highly motivated. Advanced age, however, does not preclude implantation. Patients well into their 90s can show great benefit.
Hearing through a cochlear implant is never as clear as hearing through a healthy ear. The implants allow most patients to understand speech without visual cues (for instance, talking on the telephone). For a few others, the implants make lip reading easier. In extremely rare cases, the implants have no effect.
Because a magnetic device will be implanted in your body, you may not be able to undergo MRI scans unless the magnet is removed, necessitating further surgery. As with any surgery, there is the low but finite risk of general anesthesia complications and infection, as well as device failure. The most serious risk of implantation is facial nerve injury, which occurs fewer than 1 in 1,000 cases. Recent reports also link a specific implant, one no longer on the market, with a substantially increased risk of meningitis, a life-threatening infection. With devices currently on the market, this complication is exceedingly rare, possibly no more frequent than in the un-implanted hearing-impaired population. However, vaccination for meningitis is recommended for all implant recipients.
Risks if not having this Treatments
For many patients, cochlear implantation is the only treatment that can alleviate their deafness.
It is important to perform the implantation while a child is still young, or, in an adult, as soon as possible after the patient becomes a candidate.