This collection of papers provides the reader with a contemporary summary of topics relating to the clinical application of cochlear implants (CIs). We have tried to make sure that the conclusions are based on sound evidence and that the resulting recommendations combine this evidence with clinical experience and practical considerations. The field has moved so rapidly that it is hard to be sure that recommendations will remain relevant for more than a few years. We have, however, attempted to look to the medium-term future with recommendations for both adults and children which should provide a high probability of benefit to auditory skills.
Much of the evidence collected here confirms the accepted clinical wisdom of cochlear implantation. For instance, earlier implantation in congenitally deaf children (see Leigh et al (a) and Dettman et al) was the accepted mantra well before there was solid evidence of the long-term benefits. There would be little surprise that the quality of speech production and language development in prelingually deaf adults would be somewhat predictive of their outcomes with a cochlear implant (Rousset et al). The evidence does, however, take us in directions that are at odds with accepted clinical wisdom and practice. For instance, Boisvert et al (b) summarize a number of studies that challenge the long held belief that the duration of deafness in the implanted ear is a strong predictor of outcomes. These studies, which included participants with more than 15 years of profound deafness in one or both ears, drawn from the patient populations of a number of clinics, showed no significant predictive value for the duration of deafness in the implanted ear. A better predictor appears to be the duration of bilateral profound deafness, and these studies suggest that it is mainly the loss of function in the central auditory nervous system that can have a negative impact on CI outcomes.
Three papers from the collection (Boisvert et al (a), English et al, and Plant et al) deal with the use of CIs and/or amplification in two ears, and this remains a difficult clinical area for developing prescriptive guidelines. The additional issues involved in binaural and bimodal evaluation are well covered and the need for assessments that address localization, spatially separated speech in noise, and aspects of sound quality are introduced as a necessary part of a thorough test battery. Moran et al provide some unexpected results in terms of music appreciation for CI adults, showing that sophisticated musical perception is limited for all users, but that appreciation is equally important to patient groups with very different hearing histories. Finally we have included a summary of some of the key medical and surgical issues related to CIs in children, as it is crucial for case managers to have a working knowledge of those factors and the way they may affect progress.
It is becoming somewhat of a cliché to push the need for an evidence base in making health-care decisions, but there are still many clinical fields, including audiology, where patient care is perhaps over-influenced by history, opinion, and commercial considerations. We have tried to ensure that all recommendations and guidelines in this supplement are based on good scientific evidence, but it must be said that some clinical questions cannot be easily answered from the available evidence. There is still a crucial role for the clinician to use his/her experience and knowledge, along with the evidence, to make suitable recommendations for each individual case.
Richard C Dowell