People with a certain type of hearing impairment now have a new treatment option. Today, the FDA announced the approval of the Nuclear Hybrid L24, an implant from Cochlear Ltd. The FDA has approved this device for adults age 18 and older with "severe or profound sensorineural hearing loss of high-frequency sounds in both ears," but who are able to hear low-frequency sounds either with or without a hearing aid.
According to Cochlear, the Hybrid L24 "delivers electrical stimulation directly to the high-frequency part of the cochlea." The cochlea is a snail-shaped, fluid-containing structure in the inner ear. When a person hears, vibrations move from the hammer, anvil, and stirrup bones of the middle ear to the cochlea, where they bend tiny "hair cells," which in turn bend and transmit electrical impulses along the auditory nerve to the brain, where they are interpreted as sound.
Broadly speaking, cochlear implants work by receiving sound through an external microphone, processing it, and transmitting it to a surgically implanted receiver-stimulator, through whose electrodes (threaded through the cochlea) the auditory nerve is stimulated. Cochlear explains that the Hybrid L24 uses a specialized electrode designed to "stimulate the high frequencies while preserving [...] existing low-frequency hearing." A study in the March-April 2014 issue of Ear and Hearing explains how hearing improvement from cochlear implants is measured.
Although the device has been approved by the FDA, it is not without risks. In the 50-person trial whose results were evaluated by the FDA, 68 percent of participants experienced at least one adverse event, including loss of low-frequency hearing. Generally speaking, cochlear devices implanted over the past 30 years have a revision rate of 8.3 percent and a device failure rate of 4.8 percent, with complications ranging from extrusion of the implant to infection. Regarding the Hybrid L24, the FDA states, "While the risk of low-frequency hearing loss is of concern, the FDA determined that the overall benefits of the device outweigh this risk for those who do not benefit from traditional hearing aids." The agency cautions, "Prospective patients should carefully discuss all benefits and risks of this new device with their physicians. The device is intended for use on one ear only."