A lot has changed since the first cochlear implant was performed more than 30 years ago. Successful in a wide range of patients, including the elderly, cochlear implantation is now the standard of care for treatment of severe to profound bilateral sensorineural hearing loss. And recent improvements in technology have made cochlear implants accessible to a new set of deserving patients—those with some residual hearing.
Cochlear implant candidacy has evolved dramatically since multichannel implants were first approved in 1985 for adults and in 1990 for the pediatric population. “Previously, individuals were required to have a profound sensorineural hearing loss in both ears—that is, minimal to no speech recognition—in order to be considered a candidate for cochlear implantation,” said Erin Blackburn, AuD, MS, co-director of the cochlear implant program at Duke University Medical Center in Durham, N.C. Over the past five to 10 years, the candidacy criteria have become less rigid and now include individuals with more residual hearing, Dr. Blackburn said.
“Now that we know that cochlear implants work and that the outcome is reliable for the vast majority of people, we are implanting people with moderate to profound hearing loss, not just profound hearing loss,” said Anil K. Lalwani, MD, professor and vice chair for research, director of the division of otology, neurology, and skull base surgery, and director of the Columbia Cochlear Implantation Program at Columbia University College of Physicians and Surgeons in New York City.
This is especially important for the aging population. “As we get older, we lose clarity of hearing. So, while the elderly can still hear sounds, the words are not clear. In more severe cases, they understand fewer than four out of 10 words in a sentence,” Dr. Lalwani said. “While a well-fitted hearing aid is excellent at enhancing signal-to-noise ratio, it can’t improve clarity. The cochlear implant is able to bypass the dead hair cells in the inner ear and stimulate the auditory nerve directly, thereby restoring clarity.”
Current Criteria and Controversy
Identification of candidates for cochlear implantation is a process that is still under debate. One problem is that there is not one set of criteria for candidacy. In fact, the criteria for implantation vary based on the individual manufacturers’ specifications (MED- EL, Cochlear Device, and Advanced Bionics), the Centers for Medicare and Medicaid Services (CMS) guidelines, and individual insurance carriers.
“I don’t think anyone who does cochlear implants believes that the guidelines are adequate,” said Debara L. Tucci, MD, professor of head and neck surgery and communication sciences at Duke University Medical Center and medical co-director of Duke’s cochlear implant program. “Those of us who work with these patients see a large number who fall in the middle—they are no longer benefiting from a well-fitted hearing aid, but they don’t quite meet the criteria for a cochlear implant,” she said.
In an attempt to improve the criteria for cochlear implants, a group of experts met in 2011 and modified the battery of tests used to determine implant candidacy to better reflect real-world experiences (J Acoust Soc Am. 1994;95:1085–1099; Arch Otolaryngol Head Neck Surg. 2004;130:624–628). The AzBio Sentence Test, which replaced the HINT test, uses both male and female voices speaking in normal cadence and is conducted with and without background noise. “These tests help clinicians quantify the candidates’ functional hearing before implantation, and are also important for measuring post-implant outcomes,” Dr. Blackburn explained.