University of Wisconsin–Madison

How improved cochlear implant technology benefits more patients

By Joseph P Roche, MD

According to recent estimates, hearing loss affects up to 50 million people in the United States. Learn about the different kinds of hearing loss and how recent advances in cochlear implant technology have made this option available to more patients.

Types of hearing loss

Hearing loss can be defined as the lack or loss of the ability to detect and/or understand sound. The ability to hear involves the multiple structures including the external ear, inner ear, and brain. The external ear, including the ear canal, eardrum and hearing bones, transmits sound energy to the inner ear. Diseases affecting these structures are known as conductive hearing losses. The inner ear (cochlea) and its special detector cells (hair cells) transform this sound energy into electrical signals. The hearing nerve (auditory nerve) transmits these signals to the brain, which then processes the signals and turns them into perceptions such as speech or music. Deficits affecting the inner ear and nervous system are known as sensorineural hearing losses.

The most common type of hearing losses in children are conductive losses, commonly occurring with ear infections. In adults, the most frequent type of loss is sensorineural in nature, due to loss of the inner ear hair cells and, to a lesser extent, of the auditory nerve fibers. The loss of inner ear hair cells and auditory nerves can occur from a number of pathologies including exposure to loud sounds, infections, benign tumors and familial tendencies.

Treatment options

Treatments for hearing loss depend on the location of the hearing deficit and its severity, and can range from close follow-up to hearing aids to surgical treatments. For mild to moderate hearing losses, there are a variety of devices that can help amplify sounds. For more severe losses, conventional hearing aids are commonly utilized and can be effective at allowing patients better communication and listening experiences. For profound hearing losses, special implants can be placed in the inner ear (cochlea) to stimulate the auditory nerve fibers directly. These implants can significantly improve patients’ communication abilities.

Cochlear implants vs. hearing aids

Cochlear implants have been used to restore communication abilities for the past 40 years and significant advances have been made in the last ten years. For patients with profound hearing loss, hearing aids are often not able to provide meaningful benefit. Research has shown that patients with these hearing losses may perform better with a cochlear implant than with traditional hearing aids. Additionally, new implant designs have improved these devices to allow an increasing number of people to benefit. Previously, only those with profound hearing loss were considered for implantation. Contemporary electrode designs allow for the preservation of residual hearing such that if some hearing is present (a previous exclusion criterion), the implant can still be beneficial.

For patients who elect to undergo treatment with a cochlear implant, a device is placed under the skin and a small electrode is carefully placed into the inner ear. Once healed from surgery, the patient wears a small, external speech processor that picks up sound, turns it into electrical signals, and then transmits these signals using radio waves to the implanted device. Although it has key differences, this external device resembles a hearing aid. The implant then sends the signals to the auditory nerve through the electrode. Though these signals are similar to the signals of normal hearing, they different enough that patients work with their implant team to rehabilitate their hearing. This process typically takes a number of months, but most patients begin seeing benefit within a few weeks of using the implant. Once the rehabilitation process is complete, most patients show substantially improved communication abilities. In order to determine if a person may benefit from a cochlear implant, specialized hearing assessments are required to carefully define each person’s residual hearing abilities.

For more information or treatment:

For interested individuals, the first step in the implantation process is an appointment with a hearing professional to undergo a hearing assessment. The University of Wisconsin Division of Otolaryngology in the Department of Surgery offers comprehensive hearing evaluations and treatment options, including conventional hearing aids and cochlear implantation. Interested individuals can learn more about cochlear implantation at the UW Cochlear Implant Program website or by contacting the program at (608) 263-6190.