Audiologic Management of CI Patients has become Increasingly Complex
Over the past 3 years, the Institute for Cochlear Implant Training (ICIT) Advanced Surgeons’ Training Course has provided in-depth education for over 60 CI surgeons from the US and around the world, which could improve outcomes of thousands of CI recipients. Similar training and education needs to exist for audiologists. This blog describes some of the areas that are covered in the Advanced Audiology CI Course (AAC), which was developed by ICIT to meet this educational need.
It is the responsibility of the cochlear implant (CI) team, which typically includes the implant surgeon, audiologist, and speech-language pathologist, as well as other professionals, to determine who is an appropriate candidate to receive a CI. It is also their responsibility to ensure the device is adequately placed, appropriately programmed, and to monitor device function to ensure the patient is receiving optimal benefit from its use. In recent years, the responsibilities of CI audiologists have expanded considerably and become increasingly complex as technological advances with external and internal devices have accelerated at fast rates.
Early on, many CI teams declined to implant patients with cochlear anomalies such as cochlear malformations or ossification. Today, it is estimated that approximately 20-30% of children who receive a CI have some type of cochlear abnormality.(1) This increase in access is the result of several factors, including improvements in preoperative radiographic and electrophysiologic tests(2), technological advances in internal devices (such as split and compressed arrays), and improved surgical device placement. This makes it necessary for audiologists to understand the anatomy and physiology of the ear, particularly as it relates to hearing and electrical current. For example, a patient with an ossified cochlea may receive a split electrode array. The audiologist must understand the reason for choosing such a device and be able to counsel the patient regarding expected outcomes. Mapping the device necessitates understanding the physiology of both the normal and abnormal inner ear in order to manage the flow of current that will be delivered to the electrodes located in various areas of the cochlea. This includes a basic understanding of mapping parameters that can be changed or tried when difficult situations, such as stimulation of the facial nerve, occur.
Over the years, advances in speech processing have resulted in great increases in speech recognition scores obtained by CI recipients. In early trials, adults with CIs obtained scores of approximately 15% on CNC Monosyllabic Words and approximately 35% on simple CID Sentences.(3) More recently, these scores have increased to approximately 58% for CNC Words and over 80% for the more challenging AzBio Sentences.(4) In order to optimize performance and have their patients attain such scores, CI audiologists need to have a basic understanding of sound processing strategies, as well as understand the parameters that can be manipulated or changed to optimize the patient’s ability to hear with the device. Mapping a CI comes with great responsibility; provision of an inappropriate map can result in months or years of less than optimal hearing and may lead to greatly reduced outcomes for both children and adults. Conversely, provision of an optimized map can lead to life-changing results.
Recent advances in electrophysiologic tests have increased their use in clinical care. Electric auditory brainstem response (EABR) testing has been used for several years to verify electric stimulability of the ear prior to implantation.(5) Intraoperatively, electrically evoked compound action potentials (ECAPS) have been used to determine a baseline reference for future audibility measurements when mapping the speech processor(6) while more recently, researchers have described the use of electrocochleography during surgery to help predict postoperative hearing preservation(7), and to modify surgical procedure, reduce trauma, and increase preservation of residual hearing.(8) Post-implant, ECAPS are successfully used with all 3 of the currently available devices to confirm that mapping measures of threshold, comfort level, or M level are falling within an area of audibility.
Recent approval of the Nucleus Hybrid and the MedEl EAS have increased the complexity of decisions regarding candidacy for a cochlear implant. Previously, determination of candidacy for a CI was rather straightforward: patients were only considered to be candidates for a CI if they demonstrated little or no benefit from amplification. Today, patients are being evaluated for a CI even though they demonstrate word or sentence recognition scores in the high 70s (percent correct). This is appropriate, as the results of recent clinical trials indicate that hearing preservation is possible for many patients and that such patients hear best when they are fit with devices that utilize acoustic stimulation for low frequency hearing combined with electrical stimulation for enhanced high frequency hearing. Recent studies also indicate that many patients demonstrate bimodal benefit when the hearing received with a cochlear implant is combined with the acoustic hearing in the contralateral/non-implanted ear.(9) These advances have not only changed how we look at candidacy, but have also impacted the tests being used to determine candidacy and evaluate performance. Tests are becoming increasingly complex, with greater use of more difficult sentences and increased use of test materials in noise.
Another recent change in CI management includes continued increase in the provision of CIs to pediatric patients with disabilities in addition to hearing loss.(10-11) Unfortunately, adult patients are not immune from this phenomenon; Lin and colleagues found that adults with hearing loss demonstrated a 30-40% increase in rate of cognitive decline when compared to adults with normal hearing. They also found that adults with severe hearing loss were at five times the risk of developing dementia than adults with normal hearing. Such patients can be challenging to manage and often require modifications to mapping and testing procedures in order to optimize outcomes.
Lastly, one aspect of patient management that is frequently overlooked is clinic efficiency. Recent changes in reimbursement make it necessary for audiologists to not only consider the quality of care they provide, but to also consider the sustainability of their program and the services they provide.(12) This includes designing programs that are efficient, cost-effective and will last over time to serve the life-long needs of patients with CIs.
Audiological management of CI patients has become increasingly complex. It is the responsibility of the CI team to remain current in regards to recent advances and improvements in all aspects of care. For the CI audiologist, this includes preoperative determination of candidacy, optimization of CI mapping, post-operative monitoring of device function and patient performance, and knowledge of various cochlear anomalies and disabilities and how they will impact outcomes with both children and adults. The Institute for Cochlear Implant Training (ICIT), with its introduction of the Advanced Audiology CI Course (AAC), is one option for facilitating continued learning and expansion of knowledge by CI audiologists.
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12. Huddle M, Tirabassi A, Turner L, Lee E, Ries K, Lin S. Application of Lean Sigma to the Audiology Clinic at a Large Academic Center. Otolaryng-Head and Neck Surgery 2016 Vol 154(4) 715-719.