The patient journey and when to consider a cochlear implant
As hearing decline is usually a slow process, the patient journey to cochlear implanting spans several decades (Figure 7). Initially, modifying listening environments or simply increasing the volume of phones, TV and other assistive listening device may compensate for mild hearing loss. Further progression of hearing loss impacts on the patient's family and work associates, prompting testing and the use of hearing aids. This might be all that is needed if the hearing loss stabilises; however, further decline in hearing will render the hearing aids ineffective, particularly when there is background noise or with higher frequency sounds such as children’s voices. Difficulty with phone usage follows.
When a patient's hearing loss is severe-to-profound, the efficacy of hearing aids fails, phone usage is severely limited and, unless lip-reading skills are developed and maintained, general day-to-day aural communication becomes difficult. A cochlear implant should be considered at this point.
Many adult patients have had severe hearing loss for at least 10 years before receiving a cochlear implant. The opportunity cost of hearing disability, effect on cognition and impact on socialising is measurable. It is also notable that only one in 10 adult patients with hearing loss severe enough to qualify for a cochlear implant presents for assessment. The barriers to assessment are multiple, and measures to address these are being developed. The GP has an important role in recognising suitable candidates and prompting a referral to an ENT surgeon with an interest in cochlear implantation.
Indications for cochlear implantation
The fundamental indication for cochlear implantation is bilateral severe-to-profound hearing loss for which well-adjusted hearing aids have given little or no benefit. Establishing these criteria requires a detailed and rigorous assessment of aidable residual hearing. Specially designed tests of speech perception presented to each aided ear in isolation and both ears together, under a variety of controlled quiet and noisy conditions, provide quantification of residual hearing capacity. This preimplantation data can help predict the hearing outcomes after implantation.
All patients are carefully evaluated with CT and MRI to demonstrate normal cochlear anatomy and identify any factors that may preclude accurate placement of the stimulation electrodes before undergoing cochlear implantation. Potential sources of infection should also be evaluated. Any health factors that might interfere with the anaesthesia or surgery should be identified and managed beforehand. Prospective candidates for cochlear implantation should be well motivated and supported. They need to understand the commitment required for rehabilitation and auditory training once the implant is placed. Advanced age is rarely a limiting factor for cochlear implantation.