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Interview with Derald Brackmann M.D.

Derald Brackmann, MD

June 7, 2004
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Topic: Penetrating Auditory Brainstem Implant (PABI)
House Ear Clinic
www.hei.org
Los Angeles, California


BECK: Hi Dr. Brackmann. It is always a pleasure speaking with you. I should disclose that you were one of my personal mentors, some 18 years ago, when I was working at the House Ear Clinic.

BRACKMANN: Hi Doug. I can hardly believe it was that long ago! Nice to spend time with you too.

BECK: Dr. Brackmann, if you don't mind, before we get to the PABI, would you please give me a thumbnail sketch of your professional education and career?

BRACKMANN: Sure. I graduated from the University of Illinois School of Medicine in 1962 and I did two years of post graduate training in Chicago before going into the Air Force. I was in the Air Force between 1964 and 1966 and I did my residency at Los Angeles County Medical Center in Los Angeles and completed that in 1970. Between 1970 and 1971 I was a clinical fellow at the House Ear Institute and Clinic, and then I began practice at the House Ear Clinic (HEC) and have been there ever since. I've been here for 34 years.

BECK: So you're kind of getting use to the place?

BRACKMANN: Yes, I have settled in more or less!

BECK: I'd like to discuss the penetrating auditory brainstem implant, the PABI, and the House Ear Clinic's role in this new technology. Would you tell me a little of the history?

BRACKMANN: Sure thing Doug. Drs. William House and William Histelberger first implanted an electrode onto the brainstem surface of a patient in 1979. That was a single channel device interfaced with the early single channel cochlear implant. Interestingly, that patient still benefits from that device today, she's still using it. Between 1979 and the early ''90's we went through an evolution of technology and began a collaborative project with the Cochlear Corporation (www.cochlear.com) Eventually, we interfaced a surface-based multi-electrode system that they developed, with their multi-channel cochlear implant. After successful clinical trials at HEI, that device was approved by the FDA and was used at multiple centers worldwide, and there are nearly 200 of those that were implanted as a brainstem surface electrode. The performance achieved with those was somewhat better than single channel cochlear implants, but not as good as modern multi-channel cochlear implants.

BECK: And just to be clear, you're referring to the early version of the surface-based electrodes, which were placed directly on the cochlear nucleus at the brainstem - is that right?

BRACKMANN: That's correct. Yes. We started with surface-based electrodes placed on the surface of the brainstem. However, researchers and clinicians always felt that more specific stimulation of the cochlear nucleus could produce better performance. Doug McCreery, Ph.D, and his associates at the Huntington Memorial Research Institute (www.hmri.org) worked on a penetrating electrode and developed it over the course of several years. We applied for and received approval to interface the penetrating electrode with the Nucleus 24 stimulator from Cochlear Corporation and the House Ear Institute and House Ear Clinic received approval from the FDA for a trial with a device called the Penetrating Electrode Auditory Brainstem Implant (PABI), which features a combination of penetrating and surface electrodes.

BECK: Dr. Brackmann can you tell me who the most appropriate candidates are for this, it seems it would be primarily neurofibromatosis-type II (NF2) patients?

BRACKMANN: Yes. So far it's been used exclusively in NF2 patients in this country. There have been a few other applications in Europe, but in the United States and actually, in the majority of cases worldwide, selected patients have had NF2.

BECK: And of those people with NF2, the candidates would be patients with bilateral acoustic neuromas?

BRACKMANN: That's right Doug. I'm sure you recall from your days here at the House Ear Clinic, whenever we have patients with an acoustic neuroma, or patients with bilateral tumors as may occur with NF2, we want to manage the tumors as soon as possible because when the tumors are small, we can achieve a 75% success rate in preserving hearing. Unfortunately, most patients present with tumors that are just too large to achieve hearing conservation and so for most patients in this situation, hearing conservation is not a realistic goal. In those cases, we recommend tumor removal with placement of the auditory brainstem implant (ABI).

BECK: Are other centers involved with the House Ear Clinic and Cochlear Corp on this project, or is this pretty much a HEC project at this point?

BRACKMANN: The PABI project is currently in limited clinical trials only at the House Ear Institute, and involves our colleagues from HMRI and Cochlear Corporation. The ABI, which is the predecessor to the PABI, has involved other centers. I don't know the exact number, but about a dozen centers around the United States and in Europe have been involved and have inserted the auditory brainstem implant, or ABI, with equivalent results to the House Ear Clinic.

BECK: Can you tell me a little about the specific experiences of the patients you've implanted?

BRACKMANN: Doug, we've implanted three penetrating electrodes patients combined with the surface electrode and because these patients are each unique, they are difficult to divide into groups.

The first patient had only one active electrode with the penetrating array. She is a high performer for the surface array patients, and enjoys the benefits she receives from those, but doesn't have significant additional benefit from the penetrating array. We tried to analyze why that is and apparently the electrode was placed just a little bit off. The anatomic site where it needs to be inserted is so small and the landmarks were somewhat distorted, so as you can imagine, it's not an easy thing to have exact placement.

The second patient was implanted about two months ago, and she has a beneficial penetrating electrode array as well as a useful surface electrode array. At her initial post-op she performed better than most surface electrode patients did after many months of adaptation. She is now using five of the penetrating electrodes along with multiple surface electrodes and at her initial stimulation she had some open set discrimination. She too, is a unique patient in that she had had a cochlear implant in the same ear prior to being diagnosed with a tumor. So she has a long experience with a cochlear implant in that ear, and she compares the auditory perception she receives with the PABI to her multiple channel cochlear implant. So, we're very optimistic about her longterm results. The third patient in the clinical trial was just implanted about three weeks ago and has not been activated yet, so we don't have any data on the third patient.

BECK: That is amazing. It must be very encouraging to work with patients doing as well as the second patient. She must be very grateful. Do you expect that over the long term, PABI patients will have auditory perceptions that rival modern cochlear implant users?

BRACKMANN: We'll have to wait and see. I don't know that these patients will ever compete with high performing multiple channel cochlear implant patients, but we're hopeful that we can achieve significant and highly beneficial results. Our initial FDA approval for the clinical trial for the PABI device was for five patients, and depending on how that works out, perhaps we'll apply for an extension to evaluate a few more PABI patients.

BECK: Very good, and just to be sure I understand, are you typically implanting the deep penetrating microelectrode array in tandem with the surface electrode array?

BRACKMANN: Yes, that's exactly right. There are fourteen surface electrodes and eight penetrating electrodes, and they are all implanted together.

BECK: Dr. Brackmann, it's an honor to speak with you again. Thanks for your time.

BRACKMANN: You're welcome Doug. Thanks for helping us get the word out about the PABI and the opportunities available for these patients.

For More Information:

Please visit www.hei.org
Please visit www.hmri.org
Please visit www.cochlear.com
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Derald Brackmann, MD



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