“An Introduction to Cochlear Implants” – update This note is intended to be read in conjunction with the 2002 (3rd revised) edition of this publication. Preamble The manufacturers of Cochlear Implants operate in a worldwide competitive market. The good news is that this ensures the regular introduction to the market of improved devices, offering better performance and a wider range of features for users. The bad news is that it is very difficult to keep track of all these changes within this publication! At present the Association feels that the broad picture of implant technology provided by the 2002 edition is still valid, and does not consider it appropriate to commission a full revision of our booklet. However we suggest that readers also consider the following supplementary material. Waiting Lists and Funding – page 14. This area has been impacted not only by changes in device technology and availability, but also by repeated re-organisations within the NHS. The provision of implants is regarded by the NHS as being a “Specialised Service”, which means that from 1 st April 2007 the responsibility for funding implants has been transferred to a series of Regional Specialised Commissioning Groups, one for each of the standard Local Government Regions. It is hoped that this will lead to better informed decision making on implant cases than was the case when the budgets were held at PCT level. In parallel with this the Department of Health has asked the National Institute for Clinical Excellence [NICE] to examine cochlear implant technology and recommend commissioning guidelines for use across the NHS. Unfortunately NICE do not expect to publish these guidelines until the second half of 2008, and until this happens the Regional Specialised Commissioning Groups will have to continue to use locally based decision rules. You can follow the progress of NICE’s study at: http://guidance.nice.org.uk/page.aspx?o=350200 Bilateral Implantation – not covered in 2002 edition. Most people would subscribe to the concept that two ears are better than one, and in some other European countries Bilateral Implantation – i.e. the provision of independently functioning implants on both ears - is rapidly becoming the norm, especially in paediatric cases. Unfortunately the more constrained funding environment within which most of the UK CI programmes operate means that the merits of bilateral implantation are still a matter of debate within the NHS. They are being considered as part of the NICE study discussed above. Until a considered judgement is available from NICE it is unlikely that many areas of the NHS will be willing to fund bilateral implantation, especially in adult cases. Various studies in the UK and elsewhere have shown that many patients do derive some additional benefit from the second implant, especially in terms of [i] improved ability to discriminate between speech and background noise, and [ii] some ability to identify the direction from which the sound is coming. However when these benefit are assessed using the health service’s standard cost/benefit analysis methods they do not appear to offer anything like such good value to the health service as does the provision of the first implant. In paediatric cases it can be argued that the improved speech perception in a noisy background is of particular help to children who are acquiring their basic language skills, but it is unlikely that many Regional Specialised Commissioning Groups will be willing to routinely fund bilateral implantation until the evidence being gathered by NICE is available. Combined electro-acoustic stimulation - not covered in 2002 edition. Historically there has been a group of patients who have serious hearing problems, but have retained a small element of residual hearing, and have been unwilling to take the risk implicit in having this residual hearing destroyed by the provision of a conventional implant with a full length electrode array. Typically these patients have a small amount of low frequency hearing but little or no high frequency response. Over the last 2 years or so some trials have been undertaken – mainly using devices offered by Med-El – of a technique called Combined Electro-Acoustic Stimulation, which seeks to provide an optimal solution for this group of patients. The patient is fitted with an implant which has a shorter electrode array than usual, and thence doesn’t penetrate into the inner turn of the cochlear [see the ear diagram on page 7] which provides the low frequency hearing. The patient is then given a processor which combines an implant with a conventional acoustic hearing aid in a single package, and receives high frequency information through the implant and low frequency information through the conventional hearing aid. The initial results suggest that these systems could be of considerable value to patients with this specific form of hearing loss. Choosing an Implant – page 20 All of the manufacturers have introduced upgraded models over the last few years, often featuring higher stimulation rates and a wider range of speech processing strategies. Many models include a telemetry function which allows the surgeon to confirm that the implanted part is working satisfactorily before closing the wound. Several of them now include an inductive pick up coil [for use with suitable telephones, and with hearing loops in lecture theatres etc] as a standard facility. Several models are now approved for use with low-medium power MRI scans [see page 22], and some of them also allow for the temporary removal of the internal magnet under local anaesthetic to allow the user to undergo higher powered MRI scans. Several of the manufacturers now claim a degree of water resistance for their latest processor models. A detailed analysis of the latest model ranges would date very quickly, it would be best if readers consulted the manufacturers’ web sites and the extensive literature they can supply. Speech Coding Strategy – page 23 All of the manufacturers continue to research improved Speech Coding Strategies, in many cases this work is undertaken in conjunction with major universities. A key objective is to improve speech perception in the presence of background noise, which continues to be a major concern of most implant users. The search for better Speech Coding rules is aided by the steady improvements in the technology of the implant itself. This allows the patient to be offered a choice of coding rules, and to be offered the ability to have two or more different “maps” loaded into their processor. For example one map might be optimised to pick out speech in a relatively noisy background, and another might be optimised for listening to music. Address information – inside front cover, and pages 30/31 Please note the following revised contact information:
MXM have a web site which can be found at: http://www.neurelec.com/ |