April 6, 2015
In the summer of 2014, the Centers for Medicare and Medicaid Services (CMS) delivered a potentially devastating blow to thousands of patients with conductive and single-sided hearing loss: They issued a proposal that would classify osteointegrated auditory implants (OAIs) as hearing aids, which would make them ineligible for Medicare coverage.
But calling these devices hearing aids is an incredibly simplistic view, says Johns Hopkins otologist John Carey. Through surgery, Carey and other doctors who install these devices place a titanium prosthesis just behind patients’ nonhearing ears that picks up vibrations from a sound processor sitting on top. When the processor detects sounds from the environment, the prosthesis sends vibrations through a patient’s skull bones straight to the inner ear, bypassing the structures that don’t work.
“It’s a whole new way to hear,” Carey says.
Though he knew that these devices were indispensable to his patients who received them—making continued access to them so crucial—exactly why they’re so important to recipients’ daily lives was a mystery. Data collected by former Johns Hopkins otologist John Niparko suggested that while OAIs helped patients perform better on conventional audiologic tests, they didn’t provide a dramatic improvement.
Why do Osteointegrated Auditory Implants Work?
That’s why, several years ago, Niparko asked Johns Hopkins otolaryngology researcher Bradford May if he could find the answer. May, whose research focuses on how the brain processes information, has spent decades studying how ears can derive direction and other characteristics from sound.
Because the audiologic test results were so different from patients’ actual experiences with OAIs, May wondered whether there was an aspect of how the devices were working that wasn’t being captured by the usual testing. Maybe a new test, he reasoned, might explain why patients were so passionate about these devices.
“The focus in conventional audiology is what’s going on in the ear,” says May, “but the focus I wanted in the new test is what’s going on in the brain.”
Testing the Efficacy of OAIs
To examine how OAIs truly affected patients’ function, May and Johns Hopkins audiologist Stephen Bowditch developed a test based on old aviator call signs. After assigning participants a call sign, they used recordings available in the public domain that directed patients to colors and numbers on a grid (for example, “Charlie, go to blue 2”).
The researchers found that patients with single-sided deafness did just as well on the task as volunteers with normal hearing when there was only a single voice giving a command. But when they introduced even one other distracting voice with a command for a different call sign (like, “Arrow, go to red 7”), those with unaided single-sided deafness made errors about 50 percent of the time. But when those patients were fitted with OAIs on the deaf side, their performance improved significantly—and continued to improve over time as they gained experience with their OAIs.
The problem, May says, is that without access to two different channels for sound information, usually provided by two working ears, the brain easily gets confused. “OAIs seem to be truly performing the function of the missing ear,” May says.
Making the Case to the Centers for Medicare and Medicaid Services to Continue Implant Coverage
Armed with this new information and accompanied by David Parker from Johns Hopkins’ Office of Government and Community Affairs, Carey and May, along with Johns Hopkins audiologist Colleen Ryan-Bane, who routinely fits patients with OAIs and trains them on their use, met with key staff at CMS who were responsible for deciding on Medicare coverage for OAIs. In November 2014, CMS ultimately decided to continue coverage, keeping these devices readily available for those who need them.
“It’s a testament to the incredible value of these devices,” says Carey, “and of our rigorous research program here in the department.”
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