FDA Approves First Totally Implanted Hearing System

The U.S. Food and Drug Administration today announced the approval of the Esteem – an implanted hearing system used to treat moderate to severe sensorineural hearing loss, a type of permanent hearing loss.

Sensorineural hearing loss is usually caused by genetic factors or damage to the inner ear resulting from noise, viral infections, or aging. The results are reductions in perception of sounds and in the ability to understand speech.

This differs from conductive hearing loss, which occurs when sound waves cannot transmit well through the outer or middle ear or both. Medical or surgical treatment can often restore hearing in people with a conductive hearing loss, which can be caused by earwax, fluid in the middle ear space, or a punctured eardrum.

The Esteem system consists of external testing and programming instruments and three implantable components: a sound processor, sensor, and driver. The sensor senses vibrations from the eardrum and middle ear bones and converts these mechanical vibrations into electrical signals, which are then sent to the sound processor, which amplifies and filters the signal to compensate for the individual patient’s hearing loss. The driver converts the enhanced electrical signal back to vibrations, which are then transmitted into the inner ear where they are perceived as sound.

“The approval of Esteem provides patients with an option to alleviate their hearing loss by using a device with no readily visible external components,” said Jeffrey Shuren, M.D., J.D., director of the FDA’s Center for Devices and Radiological Health.

The system is designed to alleviate the effects of hearing loss in patients ages 18 years and older. Other criteria for the device include: stable bilateral sensorineural hearing loss, a normally functioning Eustachian tube, and normal middle ear anatomy. A patient’s ability to understand speech using Esteem should be similar to that of conventional hearing aids.

In a multicenter clinical study of Esteem versus pre-implant hearing aids, 93 percent of Esteem recipients scored equal to or better than their pre-implant hearing aids on a speech intelligibility test. Seven percent scored less than with their pre-implant hearing aids, and 56 percent scored better than with their pre-implant hearing aids.

Seven percent of participants experienced facial paralysis, and 42 percent experienced taste disturbance, both of which are results of the surgical procedure necessary to implant the device. The majority of these adverse events resolved during the one-year study period.

As a condition of FDA approval, Esteem manufacturer, Envoy Medical Corporation of St. Paul, Minn., must conduct two post-approval studies. In one study, Envoy must continue to follow-up on 61 subjects from the original study for five years to study safety and effectiveness. Another study of 120 newly enrolled subjects will include an evaluation of the incidence of facial paralysis at one month after implantation, and evaluate the effectiveness of Esteem five years after implantation.

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Surviving Dance Club Music (Noise) with Hearing Intact

By tweaking a system in the ear that limits how much sound is heard, a global team of researchers has discovered one alteration that shows that the ability of the ear to turn itself down contributes to protecting against permanent hearing loss. The report appears this week in PLoS Biology.

“There’s some uncertainty in the field about what this sound-limiting system is used for,” says Paul Fuchs, Ph.D., an author on the paper and professor of otolaryngology-head and neck surgery and co-director of the Center for Sensory Biology at the Institute for Basic Biomedical Sciences at Johns Hopkins. “Now we’ve definitively shown that this system functions in part to prevent acoustic trauma.”

To get a better handle on this sound-limiting system in the ear, the research team built on previous findings in the field and focused their efforts on the nAChR protein found on so-called sensory hair cells in the ear. Nerve cells from the brain release signals that are picked up by nAChR and turn down these sensory hair cells.

The team genetically altered a single building block in the nAChR protein and tested mice for their ability to hear. “This point mutation was designed to produce a so-called gain of function in which the inhibitory effect of ACh should be greater than normal,” says Fuchs.

The altered mice were less able to hear soft sounds than normal mice, showing that the genetic alteration made in the nAChR protein did indeed further “turn down” the ear. The team then asked if the alteration in nAChR, and therefore the improved sound-blocking ability of these altered mice, also could protect from sound damage.

The team blasted 100-decibel sound at mice and again measured their ability to hear. “One hundred decibels, for me, is painfully loud, and conversation is impossible,” says Fuchs. “But sound levels in night clubs or rock concerts can be that high, and extended exposure to sound at that volume can cause hearing loss.”

They found that mice with the altered, gain-of-function nAChR suffered less permanent hearing damage compared to normal mice. “We think this pathway could be a therapeutic target for protecting from sound damage,” says Fuchs. “So far, there is little or no specific pharmacology of hearing. We’re still learning how the inner ear works. The encouraging news is that molecular mechanisms like the hair cell’s nAChR frequently involve unique gene products, so there is a real chance of finding ear-specific drugs in the future.”

Until then, Fuchs suggests limiting time spent at rock concerts, and wearing earplugs, to protect your hearing.

This study was funded by the National Institutes of Deafness and other Communication Disorders, the Howard Hughes Medical Institute, the National Organization for Hearing Research, the Tinnitus Research Initiative, the Agencia Nacional de Promoción Científica y Tecnológica of Argentina, and the University of Buenos Aires.

Authors on the paper are Paul Fuchs of Johns Hopkins; Julian Taranda, Jimena Ballestero, Eleonora Katz, Jessica Savino and A. Belen Elgoyhen of Instituto de Investigaciones en Ingenieria Genetica y Biologia Molecular in Buenos Aires, Argentina; Stephane Maison and M. Charles Liberman of Harvard Medical School; Douglas Vetter of Tufts University School of Medicine; and Jim Boulter of University of California, Los Angeles.

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