April 18, 2008 To date the the options have been limited for hearing-impaired patients who do not stand to benefit from hearing aids, but for whom cochlear implants are unsuitable because they retain some natural hearing. Now a hybrid hearing device being tested in trials across the US offers a solution to this category of patients by combining the advantages of both hearing aids and implants.
Called the DUET Electric-Acoustic System, or EAS, it is specially designed for borderline cases for which hearing aids don’t adequately distinguish sounds, but for who some natural hearing remains. For these individuals, cochlear implants that entirely replace natural hearing aren’t recommended either. Most people with hearing difficulties have one or the other device, but not both. Now initial studies on the hybrid device suggest there is a synergistic effect achieved by maintaining the natural hearing and coupling it with the cochlear implant, particularly for distinguishing speech in noisy environments. The device both amplifies low frequencies and electronically stimulates middle and high frequencies.
The EAS implant is specifically designed with a thin electrode to occupy less space in the inner ear. It is implanted by special surgical techniques to preserve natural hearing. Dr. Peter Roland, chairman of otolaryngology-head and neck surgery at UT Southwestern Medical Center, who is leading the trial, says that patients can hope to get a significant improvement in the ability to understand speech from the device, especially in a noisy situation.
The device is being evaluated by UT Southwestern otolaryngologists as part of a multi-site, national study involving about a dozen participating sites. The hybrid is already used in Europe but not yet approved for use in the US.
There is still work to be done in identifying all of the potential risks of the device. All patients are carefully screened before being admitted to the trial with the most common serious complication being loss of what hearing is left in the ear that receives the implant. The opposite ear is unaffected. Significant hearing loss has occurred in 10 percent to 15 percent of recipients to date.