Brain Implant for Deafness -- In-Depth Doctor's Interview

What is this new implant that you’re using?

Dr. Daniel Lee: This implant that we recently placed is called the Auditory Brainstem Implant. In fact, it’s not even a new implant; it was approved by the FDA about ten years ago. We are the first center to place this ABI, as it’s also known as, here in New England. The Auditory Brainstem Implant, unlike other types of hearing implants, bypasses the outer, middle, inner ears, and the auditory nerve, to actually directly stimulate or activate the parts of the brain that are responsible for hearing. We thank the generosity of Grant and Helene Wilson for supporting the development of our ABI program at Harvard/Massachusetts Eye and Ear Infirmary.

How does it compare to what a traditional implant would be like?

Dr. Lee: The traditional cochlear implant is an implant that’s placed in children and adults who have deafness, and they have a normal, or functional auditory nerve – that is, the connection between the inner ear and the brain is intact. That nerve can then carry the information from the ear to the brain. The cochlear implant is placed into the inner ear whose hair cells are not working. Those hair cells are those special cells that convert sound to a signal that the brain can understand. The implant works very well in that way, however, there are some patients who do not have a nerve that’s functional, and for that reason, these patients are candidates for this particular implant, the Auditory Brainstem Implant.

In cases of using this device, it’s the auditory nerve that’s damaged, and you need to bypass that?

Dr. Lee: Exactly. The other scenario would be if the inner ear itself was abnormal to such a degree that a conventional cochlear implant would not be able to be placed in any meaningful way.

In the patient that we’re talking about, it’s this auditory nerve that’s been damaged?

Dr. Lee: Yes, the patient that we’re talking about, on both sides, has severely damaged auditory nerves from his condition called NF2.

Right now, what can he hear without the implant being turned on?

Dr. Lee: This patient that we are referring to is an adult patient who has lost hearing over his young adult life due to a condition called neurofibromatosis type 2 or NF2. As a result, he has complete deafness now in both ears. About a decade ago, he had both tumors from both sides of his skull removed as a result of the condition and unfortunately, with the growth of the tumors and the surgical removal of the tumors, the auditory nerve was sacrificed in order to safely remove the tumors and to completely remove the tumors, so unfortunately, he has no hearing at all.

How does the surgery work?

Dr. Lee: The surgery is a combined approach. It’s a team approach involving a neuro-otologic surgeon, myself, as well as a neurosurgeon. In this case, it was Dr. Fred Barker at Mass General Hospital. We perform a craniotomy – we make a hole in the skull and we examine the area to make sure there is no more tumor left behind. We then find the brainstem to localize the cochlear nucleus – this is a very specific location where all sound originating in the ear converges upon in the brain. Once we identify that location, we then place the implant electrode into a special space, and place the electrode directly onto the surface of the brain stem itself.

What does the electrode do?

Dr. Lee: The electrode provides electrical current – it stimulates those nerves in the brainstem that are responsible for continuing to carry the signal of sound to the rest of the brain. We are bypassing the auditory nerve to directly stimulate the next level of sound processing in the brain.

Once you turn it on, what might the patient be able to hear?

Dr. Lee: We hope to give the ABI patient the ability to enhance sound awareness and improve lip reading skills. We predict performance during surgery with the expertise of our Audiology team. We monitor the electrical activity of the auditory pathways with the implant during the actual surgery itself. That way, we can predict that the location of the electrodes was accurate, that we were able to at least get some of the electrodes in the area that we need to be on, called the cochlear nucleus. We are able to actually see, by observing the waveforms generated electrical activation of the central auditory system, that in fact we are in the right location and by that, we can then predict that this patient will hopefully have some level of sound awareness with the Auditory Brainstem Implant.

What are examples of sounds he might be able to hear once you turn it on?

Dr. Lee: We would expect that he might actually have very good sensitivity to background noise or to sounds like a fire alarm, the barking of a dog, or he honking of a horn – basic sounds and tones that we hear in our environment every day are the kinds of things that we hope that he’ll be able to hear with his ABI.

There are a few patients with NF2 and the ABI that have some word understanding. Other patients actually have other conditions for which this Brainstem Implant might be helpful – other conditions that cause the nerve to be damaged or to be destroyed, but they do not have tumors otherwise, and those patients actually can do extremely well based on early clinical data from abroad.

The vast majority of patients enjoy the use of their Brainstem Implant because it really helps them to communicate through lip reading, so they can use those sound cues during conversation to help augment or improve their ability to understand through lip reading. For them, it’s a really important way to reduce the effort to communicate day to day.

When it comes to speech, what’s the hope of that when he hears people speaking?

Dr. Lee: I think there is a reasonable chance that, with time, he will be able to hear the pattern of the sound associated with the sentences or the words that are being spoken, and he can use that information to be able to help him lip read in a much more effective way. I would say that approximately 80 percent or more of these patients with NF2, with bilateral tumors who get the ABI, are able to enjoy sound perception and enhanced lip reading communication, which for them, is a tremendous improvement.

How can this technology help different kinds of patients?

Dr. Lee: In the United States, this surgery is FDA approved for use in patients with NF2 only. There are a few new studies that are just beginning here in the U.S. to try to look at other patient populations that might benefit – patients who, for example, have been in a severe car accident and where the auditory nerves are both sometimes severed. Other patients in whom the scarring from a condition like otosclerosis, a bony growth inside the inner ear, or scarring from meningitis, which would result in the inability to actually place a conventional cochlear implant – those patients might actually do very well with these. We know that from studying patients that have had the surgery in other countries and those patients have done remarkably well.

In the past, we always thought that the ABI had some limited benefits, but not as good as a cochlear implant. In fact, we’ve learned that this ABI technology may be good enough to provide speech understanding to some patients. Our work here is not only clinical. We have research efforts here – we’re trying to figure out why it is that some patients do better and others don’t, and whether we can bring that same level of performance to our tumor patients, the ones who need it the most.

END OF INTERVIEW

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