Auditory Brainstem Implant Market Poised for Growth

by James Cavuoto, editor
March 2014 issue

The market for auditory brainstem implants has seen a number of positive developments in recent years and the neuroprosthetic technology may prove to be a viable adjunct for vendors of cochlear implants. While the implantation procedure for ABIs is more complicated than for cochlear implants, and functional restoration not as great, the device delivers important benefits to a patient population with unmet needs.

In 2000, the FDA approved Cochlear Ltd.’s Nucleus 24 ABI for teenagers and adults. The system consists of a receiver/stimulator, a pocket sized speech processor worn on the body, and the microphone/headset. During surgery, the receiver/stimulator is implanted behind the ear. A wire leads from the receiver/stimulator to a series of electrodes that are implanted into the brainstem. The speech processor and microphone/headset pick up sound and change it into electrical impulses that are sent to the implanted receiver/stimulator. In clinical studies, 82 percent of implanted patients were able to detect certain familiar sounds, such as honking horns and ringing doorbells; 85 percent were able to hear and understand conversation with the aid of lipreading; 12 percent were able to hear well enough to use the phone.

MED-EL’s ABI is targeted at individuals with hearing loss due to a non-functioning auditory nerve. Bypassing both the inner ear and the auditory nerve, the device stimulates the cochlear nucleus and provides users with a variety of hearing sensations to assist with sound awareness and communication. The implant consists of an electronics housing and an implantable soft silicone matrix with a 12-contact electrode array. The 5.5 × 3.0 mm matrix is the active interface between the stimulation electronics and the neural tissue. An additional reference electrode is used for advanced telemetry measurements providing added functional reliability and control.

Last year, House Research Institute and Children’s Hospital Los Angeles announced that the FDA approved a clinical trial of an ABI procedure for children. The ABI was developed at the House Research Institute. It stimulates neurons directly at the human brainstem, bypassing the inner ear and auditory entirely. Since the procedure began, more than 1,000 adults worldwide have received the ABI.

The clinical trial is part of a unique international consortium with the University of Verona for teaching and research to advance the use of the ABI in children worldwide. The ABI is already a successful treatment with the pediatric population in Italy, and the goal of the partnership is to bring the hearing implants to deaf children in the U.S.

Earlier this year, surgeons at University Hospitals Case Medical Center completed the first ABI operation in northeast Ohio on a woman who has lost most of her hearing due to benign tumors on her auditory nerves. The procedure was performed by ear, nose and throat surgeons Cliff Megerian and Maroun Semaan, and neurosurgeon Nicholas Bambakidis.

The patient has a relatively rare genetic condition known as Neurofibromatosis Type 2. The incidence is estimated to be one in 40,000. Individuals with NF2 develop usually benign tumors on the auditory nerves of both ears. These tumors gradually compress and destroy the auditory nerves and result in bilateral hearing loss and deafness. The patient noted gradual difficulty in hearing since 2002. She had surgery and later radiation for her tumors, and was then treated with a cancer medication and a cochlear implant, but her hearing continued to decline. She has lost all hearing in her left ear and has partial hearing in her right ear.

There is great variability in terms of what and how much ABI recipients can hear. “While the effectiveness of ABI is limited, for someone who has lost most of her hearing, even having a partial return of sound is extremely helpful,” said Semaan, associate director, otology, neurotology, and balance disorders at UH and assistant professor at CWRU School of Medicine.

“The role of the audiology and intraoperative neurosurgical monitoring team is to confirm the presence of an auditory response once the ABI is placed. However, only when the ABI is fully activated 6 to 8 weeks after surgery will we be able to appreciate precisely how the patient is able to hear with the implant. An intensive auditory rehabilitation process will then begin to help the patient learn how to make use of the new sound,” said Gail Murray, director of audiology and cochlear implants at UH and associate professor at CWRU School of Medicine.

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