New research at http://www.jneurosci.org/cgi/content/abstract/27/29/7838, paper accessible only by individual or institutional subscription.
Guiraud published a paper in the Journal of Neuroscience, with results indicating that the brain reorganises its auditory pathways, and may even activate out-of-service ones upon sound stimuli, even after years of deafness. Notably, she says, “Altogether, our results strongly suggest that, after at least 3 months of cochlear implant use, the recipient’s auditory cortex presents a tonotopic organization that resembles the frequency maps of normal-hearing subjects.”
In simple terms, after 3 months of cochlear implant use, implantees’ brains look similar to normal-hearing people’s brains, at least, from an auditory perspective.
The study was supported by Advanced Bionics.
Cochlear Clinical Night
April 4, 2007
I have just come back from a Cochlear Clinical Night hosted in Singapore – the speaker was Brendan Murray, a cochlear implant specialist from Sydney. Some of you might be aware that he’s Lina Lim’s predecessor (Lina Lim is the area manager for South-East Asia), and was the first one to help set up Cochlear’s operations here in Singapore.
The talk was primarily for medical professionals and clinicians – but I found out and requested admission which was granted readily (thank you, you know who you are!) There were two main parts of the talk – clinical outcomes for Freedom, and the future of their implantable devices. Please take note scores provided below might not be accurate – they are from memory.
Cochlear did a Freedom trial on 71 postlingually deafened adults in North America. I think you should be able to know that results were fantastic according to them. Let’s go straight to the more exciting part- the implantable devices.
There are now apparently 3 new or upcoming implantable devices by Cochlear other than Freedom on the market – the Hybrid S, Hybrid L, and Auditory Brainstem Implant (ABI). The Hybrid implant is an alternative option for those who are worried about losing their residual hearing - it combines the benefits of both acoustic and electrical processing – in other words, it tries to combine the functions of a hearing aid and a cochlear implant.
The Hybrid S measures about 10mm, and is jointly developed by the University of Iowa and Cochlear. Research results on Hybrid S have shown that pitch perception scores of trial recipients can be quite close to that of normal hearing (90% in some cases, as compared to 60-70% for Long Electrode/the traditional CI).
The Hybrid L measures about 16mm, and word recognition scores have apparently created a new industry benchmark – word recognition scores hit above 50% for 3 months postoperative implantees from just around 2-6% preoperative.
The Auditory Brainstem Implant (ABI) section was very interesting. It’s an alternative for people with cochlear implant failures, or are found to be unsuitable for cochlear implants – NF2 (Neurofibromatosis Type 2), cochlear asplasia, cochlear nerve agenesis, ossified cochleas etc. It’s implanted directly at the cochlear nucleus at the right side of the brain at the bottom (if I’m not wrong), allowing direct stimulation. However, trials found that there was stimulation of other parts of the brain that was not auditory in nature, causing side effects – dizziness, aches and pain in other parts of the body ie. eyes, chest, legs.
Personally, I felt that Cochlear needs to integrate pitch perception tests as part of their testing. Not only that, I was wondering about how a bilateral and a Hybrid would compare against each other on word recognition scores (although I’m sure a Hybrid wins hands down on pitch perception). I also felt that the ABI was a kind of dead end – it had many reported side effects, and there was no complete open set recognition of words for the postlingually deafened individuals – which says a lot. Not many benefited, and those who benefited still had to use lip-reading cues to aid listening. Nevertheless, some form of listening is better than none at all – only without side effects, however!
Nevertheless, the Hybrid represents a new advancement in cochlear implants for individuals with severe hearing loss. It is much better than the long-electrode traditional cochlear implant, judging from independent research and anecdotal experiences. Individuals with such hearing loss, and are worried about their residual hearing not being utilised need not worry further with this new CI.
Hopefully, for the rest of us who are already implanted, a fully implantable device or cochlear regeneration is not too far off in the future.
In 2002, the U.S. Food and Drug Administration began investigating reports that showed a possible link between cochlear implants and a higher risk of meningitis, causing a CI manufacturer, MED-EL, to voluntarily take an implant model off the market. This link was confirmed in 2004 by a further study, that showed cochlear implants with a positioner did somehow increase the risk of bacterial meningitis. Cochlear implants without a positioner still carried a higher risk of bacterial meningitis, but not as high as those with positioners. Advanced Bionics had stopped implanting models with positioners after July 2002, and MED-EL voluntarily took their model off the market.
There is now evidence to show an association between severe hearing loss and meningitis, giving parents more to worry about. Severe hearing loss may indicate an onset of meningitis, as the incidence of bacterial meningitis has been shown to be 5 times higher in children with severe hearing loss.
So parents, if your children have hearing loss, do get them vaccinated against meningitis today. The efficacy of the vaccine is between 85-100%, and the duration of the efficacy is approximately between 3 to 5 years.
Nucleus Hybrid Acoustic + Electrical Speech Processor
March 31, 2007
Thinking of doing a cochlear implant, but worried about the side effects of losing your residual hearing?
Here is a new Nucleus processor that tries to combine the benefits of both acoustic and electrical speech processing. Developed by both the University of Iowa and Cochlear for people with good low frequency hearing but very poor high frequency hearing, this cochlear implant is different from the traditional ‘electric-only’ cochlear implant in the sense that it tries to preserve some form of low frequency acoustic hearing in the ear. It tries to do this by having a reduced diameter and length (10 mm) to limit damage to the ear
The first recipient of this new implant was Arthur Gardner who wore a hearing aid together with this CI on the same ear!
Research results on the benefits of this new implant has been promising; they report improvement in speech perception and music recognition in this group of implant users as compared to traditional long-electrode cochlear implantees. There are even reports that the pure tone recognition scores of these implant users are close to that of the control group of normal hearing people. Here are a few excerpts:
Standard CI recipients report difficulty recognizing music and familiar melodies.This group of short electrode implant users is substantially more accurate than recipients of standard CIs in melody recognition, pure tone frequency discrimination, and timbre ratings for the low frequencies.
A + E processing improved speech perception in noise by a 9 dB S/N ratio (compared with long electrode subjects).
Going out to get one already? Not yet, clinicial trials on it are still underway and it has yet to receive official sanction. But judging from results, it promises to be the next big thing in cochlear implants.
More news on it: http://seattlepi.nwsource.com/health/301568_auditory29.html
