The Hearing Assessment (Prior to Cochlear Implantation)
I will start our journey together with a discussion on the hearing assessment performed prior to cochlear implantation. Those of you who are currently going through this process are most welcome to join me as well as CI users who have already experienced the routine hearing follow-ups after implantation.
The cochlear implant candidacy process includes a medical examination, auditory assessment, and sometimes a psychological evaluation. The goal is to obtain information to provide reliable answers to two key questions:
(1) Is a cochlear implant the most appropriate hearing assistive device?
(2) Are there any medical restrictions for the surgery?
This step in the process requires the cochlear implant team to have broad theoretical knowledge and clinical experience. First the team must collect the relevant information concerning the hearing abilities of the candidate. The role of the audiologist and speech pathologist is to gather information regarding your current amplification and communication status in order to be able to compare it to your expected future outcomes using a cochlear implant.
The first step in the hearing evaluation is to have your pure-tone audiograms taken with and without your hearing aids. The audiogram determines the type and degree of the hearing loss. The audiogram can indicate the origin of your hearing loss and whether it originates in the inner ear or elsewhere. The severity of the hearing loss is reflected by the pure tone average hearing thresholds. This information serves as a key parameter in the decision regarding whether the candidate meets the audiological criteria for cochlear implantation. Information regarding which sounds are perceived best by the CI candidate is reflected by the shape of the audiogram. The audiogram also enables the audiologist to compare ears as well as aided and unaided outcomes. It is also helpful to have your past audiological records. Comparison of your audiograms over time can indicate whether the hearing loss is stable, fluctuating, or progressive.
Since the decision for implantation is based upon a comparison between the benefit you receive from hearing aids and the expected benefit from cochlear implantation, the hearing evaluation is performed with appropriately fit hearing aids.
The aided audiogram provides information regarding your current amplification. Other relevant information regarding your hearing aids includes the purchase date, recent tuning, and maintenance. Sometimes there is a need to return to the hearing aid audiologist for adjustments or overall maintenance. Occasionally, a trial period with different (better fit) hearing aids is recommended.
In order to minimize the steps to determine candidacy, my recommendation is to visit your hearing aid dispenser a month before your first visit to the CI center for any necessary refitting and maintenance. If the dispenser's recommendation is to purchase new hearing aids, you should wait until after you begin your evaluation process at the implant center to avoid wasting money if you are a good CI candidate. Sometimes, in borderline cases, candidates will be encouraged to try newer or stronger hearing aids and then be re-evaluated.
Speech Perception Evaluation
The next step of the hearing evaluation is speech perception testing. Understanding speech is a complex task; difficulty level depends on many variables. For example, when the speech stimuli provides context and verbal information (such as in tests using simple everyday sentences), a CI candidate can use this type of information to repeat sentences—even if (s)he had not understood every word. Tests that use single words are harder because they don’t provide context.
Single words perception tests can vary in their level of difficulty. The more familiar and longer the words, the easier they are to be understand. Short "nonsense” words are hardest to perceive.
Most cochlear implant teams base their evaluation on tests of both words in sentences and single words. Single word tests provide more information on the ability of the candidate to perceive the various components of speech. However, sentence tests are more reflective of the candidate's ability to manage a conversation. Since many conversations occur in noisy environments, speech perception testing is often completed in background noise to better replicate real life communication challenges.
Some candidates are unable to understand speech presented in an "open set" stimuli, as described above. For these individuals, it is common to use "closed set" tests. In "closed set" tests, the answers are presented as in a multiple-choice test.
Another communication aspect that may be evaluated is speech-reading ability (often referred as "lip reading"). This evaluates the benefit people derive from visual information such as the speaker’s lips and facial expressions combined with auditory information in order to understand speech. Gathering such data can show the positive contribution of cochlear implantation to speech reading performance. Enhancement in speech reading may also be reflected in the ease of communication reported by CI users.
Speech perception evaluation is performed for each ear separately and both ears together. The decision on whether to recommend cochlear implantation, as well as which ear should be implanted, are based upon these results.
Informal Assessment of Communication Status
Besides formal testing, there are other relevant data, usually collected through conversation or by using various self-reported questionnaires. Such data includes information on the history of the person’s hearing loss, auditory rehabilitation, lifestyle and communication challenges, and the communication modes used by the candidate.
Last but not least, a few words about expectations…
In one of the upcoming posts, I will discuss expectations about cochlear implantation. This issue continues to be relevant beyond the candidacy phase. You should feel free to discuss your expectations with your CI team. It is important that you have realistic expectations about your outcomes as well as the rehabilitation process (e.g., mapping, auditory training, and medical follow ups).
Do not hesitate to share rationale for pursuing CI as well as your dreams and future goals. Feel free to ask your team about any question you have on the process. After they have gathered all the above information, they will be able to give you reliable answers to many of your questions including examples of how the cochlear implant may affect your life. This discussion will provide you with important perspectives regarding the ongoing nature of the rehabilitation process. It will also clarify your future responsibilities to maximize your success with your new implant.