Treating hearing loss with cochlear implants
The effects of hearing loss can be devastating, no matter what the individual's age is when it occurs. Congenital or early-onset hearing loss disrupts spoken language development, which, in turn, impairs social, emotional, psychological and even physical health. Adult-onset hearing loss results in depression, social isolation, loss of employment and overall decreased quality of life.
A cochlear implant (CI) is an auditory prosthetic device used to treat debilitating hearing loss. The system includes an implantable electronics package with a lead wire that feeds an electrode array that is placed in the inner ear. An external component worn on the head collects, processes and transmits sound to the internal portion.
Surgery and activation and rehabilitation
Surgery is performed under general anesthesia and takes approximately one to three hours. The surgeon makes an incision behind the ear and creates an opening to access the inner ear. The surgeon then threads the electrode array of the internal device through this hole. The incision is closed so that the internal device is beneath the skin. Most people are able to return home the day of surgery. Two to three weeks after surgery, the external components of the device can be programmed and activated. Patients typically undergo aural rehabilitation after activation, which may include listening exercises and speech therapy to help train the brain to understand sounds heard through the cochlear implant.
The outcomes associated with implantation among adults with hearing loss that develops after a person learns to speak (postlingual hearing loss) are impressive. In fact, patients with little to no ability to understand speech with their hearing aids often hear upward of 90 percent of sentences in quiet when tested with their CI and no visual cues. The success of implant systems has led to expanding candidacy to include adults with moderate to severe hearing loss.
The Mayo Clinic Cochlear Implant Program reported 12-month postoperative speech understanding scores for a cohort of 89 adult patients implanted between 2010 and 2012. Patients included in this study had postlingual hearing loss, had not been previously implanted and were free of cognitive deficits. The ability to understand speech was tested preoperatively and then at one year postoperatively. Speech understanding was assessed using a fixed presentation level that is similar to the loudness of conversational speech, in an auditory-only condition, and in a quiet setting using single words, then sentences. Average performance repeating a single word in quiet was 9 percent preoperatively and 70 percent postoperatively. Performance using sentences averaged 14 percent preoperatively and improved to 87 percent postoperatively.
Who is a candidate?
Recent dramatic improvements in the performance of CI technology mean that a broad group of adults and children with hearing impairment can now benefit from the use of an implant system. Whereas conventional hearing aids were previously the only treatment option for many people with moderate hearing loss, adults and children with mild to moderately severe hearing loss are now considered candidates for implantation.