According to the National Institutes of Health, about 15 percent of all adults in the United States suffer from some level of hearing loss. The prevalence increases dramatically with age, with nearly half of all people age 75 and older reporting hearing loss. Although the cause varies, treatment consists of amplifying the incoming sound.
Amplification devices have improved remarkably over the past century.
At first, amplifiers were simply funnels or cones that concentrated sound into the area around the ear. The first electronic hearing aid was developed in the 1950s, and there has been continuous improvement in both function and size because of advances in the capabilities and the miniaturization of electronics.
Digitization has allowed exquisite control and amplification of the incoming sound at the individual frequency level to accommodate individual differences in hearing loss.
In the 1970s, a revolutionary improvement occurred with the advent of the cochlear implant, which directly stimulates the auditory nerve within the cochlea.
In all hearing devices, at least one component is outside the body and subject to the external environment — at least until recently.
A few months ago, the FDA sent Envoy Medical in St. Paul a formal premarket approval letter for its device, Esteem, the first fully implanted inner ear stimulator approved to treat moderate-to-severe hearing loss. Note that Envoy does not call the device a hearing aid, but rather, a hearing system because it does not actually amplify sound; it amplifies movement of the ear drum.
The Esteem system includes three components: sensor, sound processor, and driver. These are placed under the skin behind the ear and in the middle ear, making this device independent of the external environment. The system also includes testing and programming devices that are not implanted.
How it works
The sensor picks up vibrations from the eardrum and middle ear bones, and a transducer converts them into electrical signals that go to the processor for amplification and filtering to customize the device for the individual patient’s hearing loss profile. The driver then converts the enhanced electrical signal into vibrations so the inner ear can perceive them as sound. This is a different process from the typical hearing aid that amplifies sound and basically uses a small speaker to then create the sound waves that hit the eardrum.
Because this device is surgically implanted, it faces challenges that a traditional hearing aid does not. Potential complications include scar tissue buildup and infections around the incision. Because of the unique nature of this device and the fact that it requires a surgeon’s order or prescription, Envoy and the FDA have created a list of indications and contraindications to help surgeons determine whether the product is right for a potential candidate (see Envoy Medical’s Web site, https://esteemhearing.com/important-safety-information/, for information about indications and contraindications.)
The clinical trial that led to approval was a multicenter, one-arm, non-randomized, non-blinded study that began in early 2008. The post-implant outcomes were compared to each subject’s pre-implant baseline “hearing aided” condition.
Note that the outcome was not compared to the patient’s hearing without the use of a traditional hearing aid.
Follow-up was scheduled for 4 months and 10 months post-op and then yearly.
There were two measured primary effectiveness endpoints: The Esteem system would provide at least a 5-decibel hearing advantage over the traditional hearing aid, and word recognition would improve.
In addition, secondary endpoints were pure tone average hearing, hearing of speech in a noisy environment, and quality of life. A detailed review of the improvements is beyond the scope of this article but suffice it to say that the device produced significant improvements toward both the primary and secondary endpoints.
In addition, the Esteem did not lead to a decrease in cochlear function.
That said, severe adverse effects occurred in 10.5 percent of patients and included severe pain and facial weakness (reported by one subject), infection at the incision site (reported by one subject), limited benefit (reported by three subjects) and incision breakdown (reported by one subject). All of these events were resolved with either medication, revision procedures with replacement of the device, or permanent removal of the implant.
All three patients with limited benefits had developed extensive fibrous adhesions that interfered with the ability of the device to increase the vibrations needed for hearing improvement.
There were 96 other mild and moderate adverse events. At the one-year reporting time, 70 percent of these had been resolved, with the remaining rated as unresolved.
The unresolved mild and moderate adverse effects included taste disturbance, facial weakness/paralysis, tinnitus, dizziness, middle ear effusion, and ear pain.
Managed care implications
Hearing benefits are not uniform among the many insurance plans in the United States. They tend to be rather basic and aimed at functional improvement.
Of course, cochlear implants are typically a covered benefit, but require prior authorization. Most plans do not attempt to direct members to a preferred device but allow the health care provider to direct the acquisition of a hearing aid.
What subgroup of patients would benefit from the Esteem? What attributes of the Esteem will compel payers to cover this device?
Obviously there are some patients who cannot tolerate a hearing aid mold because of deformities of the external ear and ear canal. Other patients may have a difficult time using an external device because of exposure to the elements; scuba divers come to mind. Many other considerations will need to be explored for answers.
One thing is for sure: The Esteem Hearing System again demonstrates how engineers, physicians, and researchers are continuously searching for Tomorrow’s Medicine!