Travis Isaacs highlights what makes auditory brainstem implants different from other forms of treatment for impaired hearing
There is a long history of people using technology to make the most of their hearing, but it’s only relatively recently that such solutions have proved truly effective for large numbers of people. Modern micro-technologies are currently enabling the creation of discreet and reliable solutions for hearing impaired people – something that for many, will represent a dream come true.
Among them is a group of people that are only now beginning to experience any sort of auditory sensation at all. A small proportion of children are born every year without a cochlea – a delicate mechanism of the inner ear that picks up sound vibrations and transmits corresponding signals to the brain. Some simply don’t possess the nervous circuitry required to transmit those stimuli, while others may have lost theirs due to infections such as meningitis.
Children in whom such mechanisms are absent simply don’t have the means to experience any kind sound at all, no matter how loud it may be. It will also mean that standard cochlear implants will be useless, since these devices rely on the presence of the cochlea and associated nervous pathways in order to function.
However, there is now a revolutionary solution known as an auditory brainstem implant (ABI), which more or less does what its name suggests. Rather than using electrodes to connect sound vibrations to the inner ear, as with a cochlear implant, ABI electrodes are instead connected directly to the brainstem, in effect bypassing the body’s standard hearing system altogether.
The procedure involved in fitting an ABI is extremely delicate and considerably more invasive than that needed for a cochlear implant but, the results are proving to be profoundly life-changing for those people who have undergone the operation.
World of speech
It’s important to note that an ABI cannot fully replicate the fine-grained frequency separation of the natural cochlea. Thanks to the way in which the cochlea is formed, it is able to detect and identify very fine distinctions between sound frequencies. It’s what allows us to distinguish between different speech sounds – the perceptual difference between ‘s’ and ‘sh’ speech sounds, for instance, is merely a matter of sound frequencies.
An ABI does not quite allow for that level of distinction, but it can enable the user to tell the difference between stressed and unstressed speech and gauge its rhythm and speed. When allied to lip-reading abilities, an ABI can open up the world of speech to people who might otherwise never register it at all. It can also make a host of environmental sounds audible to someone for the first time, with obvious benefits.
The technology has been available to children in Europe for some time, but has only recently been sanctioned by health authorities in the US. For the parents of children born deaf and children themselves, the solutions now made possible by digital technologies are something they could once only have dreamed of.
Anyone concerned for their own hearing or that of a family member at any stage of life can receive comprehensive audiology tests and find a range of solutions at Hidden Hearing, one of the UK’s largest audiology providers – for more information, contact 0800 740 8706 or visit the Hidden Hearing website.