Written by Professor Iain Bruce for Doctify
Conventional hearing aids just aren’t powerful enough anymore? Your child is not reaching speech, language & educational milestones despite wearing a powerful hearing aid? Powerful hearing aids help, but you’re exhausted at the end of the day because of the effort of listening?
Have your questions answered by Professor Iain Bruce of the Manchester Children’s Ear Nose & Throat Clinic – aspects of this article are based on the chapter Professor Iain Burce wrote with Ingo Todt (Berlin) on Hearing Preservation Cochlear Implant Surgery, in Advances in Hearing Rehabilitation. Karger Publisher (2018).
What is Hearing Preservation Cochlear Implantation?
It is no longer the case that Cochlear Implantation (CI) is only appropriate for children, young people & adults with little or no usable hearing. There is a widely held misconception that patients with profound high-frequency hearing loss and residual low-frequency hearing in the normal-to-moderate hearing loss range, would not be offered CI; with this decision being influenced by concern about losing the benefit from residual natural hearing after surgery, or a believe that residual hearing was too good or good enough to receive substantial benefit from modern conventional hearing aids.
The development of CI electrode arrays and surgical techniques (‘soft surgery’) aimed at minimising intra-cochlear trauma following array insertion, has been one of the most significant advances in the field of CI. Ultimately, the aim of hearing preservation (HP) CI being that patients can hear high-frequency sounds ‘electrically’ and low frequency sounds either ‘naturally’, or with the aid of ‘acoustic stimulation'( combined CI + hearing aid). Sometimes this is referred to as ‘electroacoustic stimulation’ (EAS). The potential benefits of EAS include improved listening in background noise (real-life listening), greater enjoyment of music, and a better appreciation of the meaning of intonation & stress in speech.
What Factors Influence Hearing Preservation After Cochlear Implants?
The factors influencing successful HP remain under investigation, but several factors are thought to be important: surgeon’s skill, electrode design (dimensions and stiffness), atraumatic insertion, steroid use, age and as yet unknown patient factors. Certainly, it is possible to perform an uneventful ‘textbook’surgery with resultant wide variability in the preservation of natural hearing. As such, patients should be counselled about the chance of successfully preserving residual hearing after CI ( varies between 50 -95+%). The strengthening evidence detailing successful hearing preservation using ‘standard’ length electrode arrays is such that I now avoid using the generation of ‘bespoke’ short electrode arrays designed specifically for hearing preservation. These short electrode arrays may have slightly higher hearing preservation rates, but the patient may be worse off if the residual hearing is lost at surgery, or in the years that follow. I believe that it is better to have electrodes switched-off and sequentially activated to match hearing deterioration over time than to be faced with a second surgery to insert a ‘standard’ length electrode array or accept a sub-optimal long-term outcome.
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