You may have heard of an auditory brainstem implant (ABI), which is used for people whose auditory nerves are no not functional. Here’s an introduction to the ABI.
January 2004 – Here’s some information on the first major upgrade we’ve seen to the ABI.
April 2004 – And here’s a followup on the first two patients implanted with the Penetrating ABI.
May 2006 – ABI Sends Sound Signals Directly to Brain
December 2008 – University of Illinois Physicians Perform Auditory Brainstem Implant
May 2009 – First Auditory Brain Stem Implant in New England
July 2009 – Auditory Brainstem Implant “Solves” Missing or Damaged Auditory Nerve
March 2010 – Karen Lichtefeld and the Auditory Brainstem Implant
May 2010 – Neuron research could improve auditory brainstem implants
March 2011 – Auditory Brainstem Implants
Most readers are familiar with the cochlear implant (CI), but how many have heard of a related device called the auditory brainstem implant (ABI)? The ABI, like the CI, replaces part of the hearing mechanism that is not working properly. Whereas the CI is implanted in the cochlea and replaces the function of defective hair cells, the ABI is implanted in the brainstem, and replaces the function of a defective auditory nerve.
The ABI may be an appropriate treatment regardless of the cause of the auditory nerve problem. It may be used most often in patients who become deaf due to neurofibromatosis Type II (NF2). This disease causes tumors on the cranial and spinal nerves. Removing those tumors often requires severing the auditory nerve, which destroys the hearing in the affected ear. Bilateral surgeries can destroy the hearing in both ears.
Traditional CIs are ineffective in these cases, because they rely on the auditory nerve to transmit signals from the cochlea to the brain. But the ABI bypasses the auditory nerve to inject acoustic information directly into the brain.
The recently approved device is the Nucleus 24 Multichannel Auditory Brainstem Implant from Cochlear Corporation. It is approved for use in teens and adults with NF2. An evaluation of the device in 60 patients revealed that 82 percent were able to detect environmental noise. The majority of these patients reported that the ABI assisted their lipreading, and a few were able to use a voice telephone. Eighteen percent of the patients derived no benefit from the ABI.
For additional information, point your browser to www.cochlear.com.
New ABI is inserted INTO the Brain Stem
We recently published an article about auditory brainstem implants (ABIs) and explained that they are used by people who have had their acoustic nerve severed, usually as treatment for neurofibromatosis, type 2 (NF2), a disease which causes tumors on various nervous tissue throughout the body. We reported that ABIs recipients are generally unable to understand speech without lipreading, and one of our readers responded that she is somewhat capable of doing so.
Doctor Bob Shannon of the House Ear Institute has recently implanted new ABIs into two patients. These ABIs differ from previous ones, in that they are inserted into the brainstem, rather than just lying alongside it. While this technique offers the possibility of improved performance, it is carries significantly more risk than the older ABIs. Because the brainstem carries nerve signals from throughout the body, damage to any portion of it can have serious and irreversible effects.
The new ABI has eight electrodes of varying lengths, intended to provide eight channels of acoustic information (vice only one channel from a traditional ABI). Dr. Shannon believes that the additional acoustic information may result in much better speech understanding than with a traditional ABI.
PABI Progress Report
Editor: In Volume 18 Issue 3 we reported on the Penetrating Auditory Brainstem Implant (PABI), a new device similar to a cochlear implant, but designed for people whose auditory nerve is not intact. Here’s an update on the progress of the recent implantees. We were unable to get permission to republish this article, so here are the first couple of paragraphs. If your interest is piqued, the article is available here.
Researchers at the House Ear Institute in Los Angeles recently reported success with two patients who were implanted with the new penetrating electrode auditory brainstem implant (PABI) as part of a clinical trial.
Molly Brown, one of the recent implantees, received the PABI in November 2003. In mid-January this year, House Ear staff turned the device on, and she was learning how to understand speech again with the technology, reported David Lim, MD, head of House Ear’s Department of Cellular and Molecular Biology, during a recent press conference. [Editor’s note: At press time, House Ear staff reported that Brown was progressing well with her PABI and hearing more sounds every day as she becomes more accustomed to the device.]
“I’m very happy to be here to talk about my implant,” said Brown at the press conference. “I am happy to participate in the clinical trial.”
When hearing aids lose their effectiveness in providing effective communications, many people turn to the cochlear implant for improved understanding. Cochlear implants are great for those who have intact auditory nerves. But what about people whose auditory nerves are not intact? They can use an auditory brainstem implant (ABI)!
Auditory Brainstem Implant “Solves” Missing or Damaged Auditory Nerve
An auditory brainstem implant (ABI) treats deafness caused by damage to the vestibulocochlear nerve due to tumors or surgery. Specifically, an ABI involves the placement of electrodes in the cochlear nucleus, which is responsible for processing sound signals received from the ears and is located in the lower part of the brain called the brainstem. The ABI provides a sensation of hearing to deaf people by directly stimulating the brainstem. Because it bypasses the cochlear nerves, the device is most useful for people whose cochlear nerves are absent or do not function properly.
Karen Lichtefeld and the Auditory Brainstem Implant
Neurofibromatosis Type II (NF2) is a life-threatening, genetic disease of the nervous system characterized by bilateral, non-cancerous fibrous tumors-also referred to as vestibular schwannomas or acoustic neuromas- that grow on the vestibular nerves. Current treatment options include surgery that usually requires severing the hearing or auditory nerve. If the auditory nerve is cut, a cochlear implant cannot be used to treat an individual with NF2 because the auditory nerve is then not able to carry signals from the cochlea to the cochlear nucleus in the brainstem. In such cases, an NF2 patient may benefit from an auditory brainstem implant (ABI), designed to stimulate the auditory portion of the cochlear nucleus in the brainstem and send sound signals directly to the brain.
Auditory Brainstem Implants
by Robert V. Shannon
Although cochlear implants (CIs) are highly successful at restoring functional hearing, some people have no remaining auditory nerve and cannot benefit from a CI. These patients have lost their auditory nerve (VIIIn) from a variety of causes, most commonly neurofibromatosis type 2 (NF2). NF2, a genetic defect on chromosome 22, causes tumors originating in the Schwann cells that insulate the auditory nerve where it exits the internal auditory meatus. When the tumors are removed the auditory nerve is usually cut and no connection exists between the still-functioning cochlea and the brain. Other causes of VIII nerve loss are temporal bone fracture, congenital aplasia of the cochlea and/or nerve, and severe ossification from congenital or post-meningitic growth. The auditory brainstem implant (ABI) is similar in design and function to a CI, except that the electrode is placed on the first auditory relay station in the brainstem, the cochlear nucleus (CN).