4. Device activation

It is our practice to provide two initial programs. The first is a standard, default program recommended by the manufacturer's specifications, and the second has frequency-to-electrode allocation, as indicated above, based on the surgical outcome indicated by X-ray findings for the particular patient. We ask the new user to switch between the two programs in order to experience whether one is more pleasing and/or effective than the other. We speculate that postlinguistically deafened adults will have difficulty adjusting to the sound quality for the standard program and choose the second that was derived from the intraoperative findings and one that avoids a "boomy" sound indicative of a mixing up of low-frequency sensations produced by apical cross-turn stimulation.

The second program will usually take into consideration the possible frequencyplace mismatches relative to insertion depth, that is, the physical position of the electrode contacts. The default frequency allocations provided in the programs of the sound processor may need adaptation [1], as discussed above.

All new users are sent home for a month after receiving counseling about ways in which they can direct their own rehabilitation through practice at home and in different environments in which they commonly find themselves. They are also reminded of expectations, and family members and/or significant others are provided counseling in ways to support the new CI user. It is an option to test the subject for sentence understanding in quiet during the first days of activation. We have found that if a new user scores >60% at day 1, they will obtain scores >80% by the 1-month follow-up (Figure 2). These CI users will likely need little active rehabilitation and already appear to be on a good course. Thus, early performance is indicative of later, long-term performance.

Figure 2 Sentences in quiet evaluated at 1 day and at 1 month, post-implant.

Prognostics Factors of Cochlear Implant in Adults: How Can We Improve Poorer Performers? DOI: http://dx.doi.org/10.5772/intechopen.89577

In fact, the development of speech understanding with a CI does not follow a linear function with time. High sentence recognition scores can be obtained at only 1 day after activation, and the first 2 weeks are as important as the next 6 months and the following 2–3 years. It is not fully understood why CI user's individual performance progress at different rates. In James et al. [1], they observed different patterns of growth in scores, both in quiet and in noise, from the first month, but always following a logarithmic growth curve, such that each additional increment in performance took twice as long as the preceding increase.

### 5. Optimizing maps and initial evaluations: 1-month follow-up

Significant improvement will usually take place from activation to 1 month; thereafter increases continue but at a much slower pace. Increases in understanding will be about the same after 6 months of experience for sentences in quiet. Adapting to any new sensation requires time; an auditory signal presented through a CI will always first be perceived as very different. It is unclear why some new users immediately accept the new input and others reject it as sounding too foreign. In any case, we believe a month of exposure to the new signals is the minimum time to allow all patients for the initial accommodation to the input. Thus, all CI users are re-evaluated at 1 month.

By the first month, there already is access to data logging to confirm speech processor program usage, the users are usually aware of which program they might prefer, and the speech recognition scores in quiet will have been tested. The outcome of sentence recognition testing and CI user reports may indicate a need for alternative device programming. Looking at Tables 1 and 2, approximately 40–50% of the variance is not explained by the patient-related and surgical factors. There are dynamics in play that may never be known such as the impact of certain disadvantages (insertion depth, dislocation, cochlear condition at surgery) and others. Alternative programs (differing mapping parameters) may also take into consideration speed of stimulation (refractory period) as demonstrated through different stimulation rates or spread of excitation via channel selectivity (perhaps deactivating particular electrodes). These more advanced aspects of programing, however, are taken into consideration at every programming session, as indicated. Optimizing sound processor programs is the most direct way to compensate for the degraded speech signals delivered through a cochlear implant.

The one aspect to be evaluated may be behavioral responses to changes in stimulation rate. Postoperative NRT testing may be indicated to assess neural recovery functions to gain information about beneficial stimulation rates. From their studies on the temporal characteristics of auditory nerve stimulation via CIs, [16] suggest that the programmed stimulation rate relates to the refractory period of the nerve. CI user performance may be addressed, in some cases, by reducing the stimulation rate. It is not possible to define when the so-called aging process begins, but it is clear that neural transmission times slow as one ages [17, 18]. Older CI users may be more susceptible to stimulation rate effects. Any means of enhancing auditory signals that occur in the presence of poor temporal processing will provide a better foundation for learning to overcome perceptual difficulties.

#### 5.1 Initial performance evaluations

During this test interval, it is possible to identify, with more clarity, the individuals who might be classified as potentially having poor performance. By definition, on average, approximately 50% of recipients will demonstrate "normal" performance, i.e., 70% or greater scores for sentence understanding in quiet. However, if

close enough to activate auditory nerves. Those outside, mislocated into the scala

It is our practice to provide two initial programs. The first is a standard, default program recommended by the manufacturer's specifications, and the second has frequency-to-electrode allocation, as indicated above, based on the surgical outcome indicated by X-ray findings for the particular patient. We ask the new user to switch between the two programs in order to experience whether one is more pleasing and/or effective than the other. We speculate that postlinguistically deafened adults will have difficulty adjusting to the sound quality for the standard program and choose the second that was derived from the intraoperative findings and one that avoids a "boomy" sound indicative of a mixing up of low-frequency

The second program will usually take into consideration the possible frequencyplace mismatches relative to insertion depth, that is, the physical position of the electrode contacts. The default frequency allocations provided in the programs of

All new users are sent home for a month after receiving counseling about ways in which they can direct their own rehabilitation through practice at home and in different environments in which they commonly find themselves. They are also reminded of expectations, and family members and/or significant others are provided counseling in ways to support the new CI user. It is an option to test the subject for sentence understanding in quiet during the first days of activation. We have found that if a new user scores >60% at day 1, they will obtain scores >80% by the 1-month follow-up (Figure 2). These CI users will likely need little active rehabilitation and already appear to be on a good course. Thus, early performance is

vestibuli, may yield no NRT response [13].

Advances in Rehabilitation of Hearing Loss

sensations produced by apical cross-turn stimulation.

indicative of later, long-term performance.

Sentences in quiet evaluated at 1 day and at 1 month, post-implant.

Figure 2

146

the sound processor may need adaptation [1], as discussed above.

4. Device activation

we consider individuals who present with no negative patient-related factors, they should perform better than 70% and on average around 90%. This is, then, the second use of the model. The prediction of the model is compared with the actual score at 1-month post-activation; if the actual score is lower than the prediction, it points to a need for remedial action. Thus, two groups are identified who will undergo further evaluation: those individuals who are overall "poor" performers and achieve less than 70% and those whose actual scores are below their predicted scores from the model. The others with satisfactory performance will be advised to continue their own patient-directed practices (passive rehabilitation). Complete remediation of the effects of duration of deafness and congenital hearing loss would result in a "corrected" distribution as shown in Figure 1, with an overall average (median) performance at about 90% and only 25% of cases performing less than 70%. Such an improvement is the aim of the remedial actions described in the following sections.

Figure 3 illustrates the further needs of the less-than-satisfactory poor user or overall poor performer. The results of intraoperative NRT findings are compared, and mapping considerations are applied to create alternative programs, as described above. This is considered part of the bottom-up approach. Other, more specific analytic psychophysics may also be included in a rehabilitation program, if indicated [5].

demonstrating poor working memory lead to applying auditory cognitive training; however, if the results of the evaluations point to an abnormal working memory

Prognostics Factors of Cochlear Implant in Adults: How Can We Improve Poorer Performers?

It is beyond the scope of this chapter to supply specific evaluation and training materials. Methods should be consistent with culture and the available materials in a particular language and according to the consensus within the country. A review of rehabilitation methods that can be applied to cochlear implant users can be found in [19] and in [20]. In common, however, is that counseling will focus on the CI user gaining confidence in associating the digitally coded sounds that are presented through a CI with meaningful speech. It is advisable to remember that a CI user needs adequate time to experience modifications; even poorer users do not require constant reprogramming. In general, poorer users are seen at the clinic in 3-month intervals, and better performers are seen in 6-month to annual intervals. Interactions with local speech-language therapists are the main support for poorer performers with frequent liaison between the therapist and specialists within our clinic.

Harris et al. [2] point out that no standardized rehabilitation approach exists despite decades of CI use in individuals of all ages. Agreement is found in the concept of tailoring post-implant rehabilitation to the needs of the individual user [21, 22]. The challenge is that long-term rehabilitation may be indicated but that limitations in funding through reimbursement are available mainly due to a lack of evidence for demonstrable effects [2, 18]. Our experience, and that of [21], indicates that rehabilitation may be required for as long as 2 years to reach a so-called

Conceptually, rehabilitation can be divided into two approaches, top-down or bottom-up [23]. Methods that focus on bottom-up procedures utilize materials relating specifically to the input signals possible via a CI, that is, how a signal is processed. The elements of sound serve as building blocks, starting with the smallest unit (i.e., a phoneme). Relative to a CI, acquiring responses to the psychophysical tasks (temporal, spectral, and amplitude cues) during the mapping process entails a bottom-up approach, which is an analytic method. Some of these tasks may

Top-down methods represent a synthetic approach and have the aim of enhanc-

ing communication strategies through cognitive processing. As mentioned,

and phonological sensitivity, neurocognitive evaluations are pursued.

Indications for rehabilitation training in poorer performers.

DOI: http://dx.doi.org/10.5772/intechopen.89577

5.2 Rehabilitation approach

Figure 4.

performance plateau.

149

be adapted for auditory training purposes [5].

5.2.1 Synthetic-cognitive training (top-down)

A poor performer will require thorough auditory evaluations and cognitive testing. Given that the predictive model accounts for approximately 63% of the variance in performance, the contribution of cognitive factors must be considered. If poor performance is identified or suspected, steps are taken to investigate the factors that may be affecting the user's ability to process the sound information they are receiving through the CI including the central aspects of linguistic and neurocognitive skills influencing communication strategies as outlined in Figure 4.

Evaluations that yield scores within normal limits for phonological sensitivity and working memory point to motivation issues and, therefore, intense counseling are provided without the need for active rehabilitation support. If poor linguistic skills are revealed, training in phonological aspects is indicated. Evaluations

Figure 3. Flow diagram illustrating the development of patient-specific rehabilitation strategies.

Prognostics Factors of Cochlear Implant in Adults: How Can We Improve Poorer Performers? DOI: http://dx.doi.org/10.5772/intechopen.89577

Figure 4.

we consider individuals who present with no negative patient-related factors, they should perform better than 70% and on average around 90%. This is, then, the second use of the model. The prediction of the model is compared with the actual score at 1-month post-activation; if the actual score is lower than the prediction, it points to a need for remedial action. Thus, two groups are identified who will undergo further evaluation: those individuals who are overall "poor" performers and achieve less than 70% and those whose actual scores are below their predicted scores from the model. The others with satisfactory performance will be advised to continue their own patient-directed practices (passive rehabilitation). Complete remediation of the effects of duration of deafness and congenital hearing loss would result in a "corrected" distribution as shown in Figure 1, with an overall average (median) performance at about 90% and only 25% of cases performing less than 70%. Such an improvement is the aim of the remedial actions described in the

Figure 3 illustrates the further needs of the less-than-satisfactory poor user or overall poor performer. The results of intraoperative NRT findings are compared, and mapping considerations are applied to create alternative programs, as described above. This is considered part of the bottom-up approach. Other, more specific analytic psychophysics may also be included in a rehabilitation program, if indi-

A poor performer will require thorough auditory evaluations and cognitive testing. Given that the predictive model accounts for approximately 63% of the variance in performance, the contribution of cognitive factors must be considered. If poor performance is identified or suspected, steps are taken to investigate the factors that may be affecting the user's ability to process the sound information they

neurocognitive skills influencing communication strategies as outlined in Figure 4. Evaluations that yield scores within normal limits for phonological sensitivity and working memory point to motivation issues and, therefore, intense counseling are provided without the need for active rehabilitation support. If poor linguistic skills are revealed, training in phonological aspects is indicated. Evaluations

are receiving through the CI including the central aspects of linguistic and

Flow diagram illustrating the development of patient-specific rehabilitation strategies.

following sections.

Advances in Rehabilitation of Hearing Loss

cated [5].

Figure 3.

148

Indications for rehabilitation training in poorer performers.

demonstrating poor working memory lead to applying auditory cognitive training; however, if the results of the evaluations point to an abnormal working memory and phonological sensitivity, neurocognitive evaluations are pursued.

It is beyond the scope of this chapter to supply specific evaluation and training materials. Methods should be consistent with culture and the available materials in a particular language and according to the consensus within the country. A review of rehabilitation methods that can be applied to cochlear implant users can be found in [19] and in [20]. In common, however, is that counseling will focus on the CI user gaining confidence in associating the digitally coded sounds that are presented through a CI with meaningful speech. It is advisable to remember that a CI user needs adequate time to experience modifications; even poorer users do not require constant reprogramming. In general, poorer users are seen at the clinic in 3-month intervals, and better performers are seen in 6-month to annual intervals. Interactions with local speech-language therapists are the main support for poorer performers with frequent liaison between the therapist and specialists within our clinic.

#### 5.2 Rehabilitation approach

Harris et al. [2] point out that no standardized rehabilitation approach exists despite decades of CI use in individuals of all ages. Agreement is found in the concept of tailoring post-implant rehabilitation to the needs of the individual user [21, 22]. The challenge is that long-term rehabilitation may be indicated but that limitations in funding through reimbursement are available mainly due to a lack of evidence for demonstrable effects [2, 18]. Our experience, and that of [21], indicates that rehabilitation may be required for as long as 2 years to reach a so-called performance plateau.

Conceptually, rehabilitation can be divided into two approaches, top-down or bottom-up [23]. Methods that focus on bottom-up procedures utilize materials relating specifically to the input signals possible via a CI, that is, how a signal is processed. The elements of sound serve as building blocks, starting with the smallest unit (i.e., a phoneme). Relative to a CI, acquiring responses to the psychophysical tasks (temporal, spectral, and amplitude cues) during the mapping process entails a bottom-up approach, which is an analytic method. Some of these tasks may be adapted for auditory training purposes [5].

#### 5.2.1 Synthetic-cognitive training (top-down)

Top-down methods represent a synthetic approach and have the aim of enhancing communication strategies through cognitive processing. As mentioned,

outcomes of the predictive model accounted for more than 60% of the variance in quiet and 50% of the variance in noise for sentence recognition scores obtained at 1 month after CI activation [1]. Thus, cognitive factors play a large role in the wide variance seen in performance scores obtained by the adult CI population. Optimizing a personalized rehabilitation strategy must take into consideration the cognitive dynamics of speed of processing, working memory, and attention and executive function [23].

Increases continue even up to 3 years, but the incremental gain is much less that

Prognostics Factors of Cochlear Implant in Adults: How Can We Improve Poorer Performers?

We summarize the complete rehabilitation process in Figure 5. Pre-implant counseling based on the results of the predictive modeling; surgical planning focusing on considerations to the size of cochlea and type of electrode; and intraoperative testing using X-ray findings to confirm placement and depth of insertion along with NRT to confirm neural interface via electrostimulation all take place before initial activation. This includes counseling that may need to modify expectations based on surgical outcomes and intraoperative evaluations. Two MAPs are developed at first fitting where one is based on intraoperative findings. At 1 month, observations gathered from data logging, along with comparing sentence scores in quiet to the predictive model, provide an indication as to whether a new CI user will need specialized rehabilitation. Again, counseling may need to guide and modify expectations. The type of rehabilitation is determined, usually a combination of both bottom-up and top-down approaches. At the 6-month interval, testing in noise is applied, and further adaptations to the MAPs are made. In the future, we hope to extend the predictive model to include factors for analysis of performance in noise for the long term. Continued appropriate rehabilitation after 6 months ensues, and continued counseling insures that the CI user understands the need to support

Providing viable rehabilitation to adult poor performers lies within the realm of

As CI specialists, we provide access to direct rehabilitation and rehabilitation support. Specialized rehabilitation, given the wide variability in patient outcomes,

detective work. In the early stages, it provides affirmative counseling based on predictive modeling and effective surgical planning and its implementation. Counseling patients with realistic expectations, however, takes place throughout the entire rehabilitation process. There will always be differences in outcomes, but having a full array of options based on objective measures and individual case history will guide the specialist to advise for optimal use of their hearing abilities. Motivation is a very important component of success, and this needs to be reinforced especially for this population who, often, have unrealistic expectations

what is usually seen during the first 6 months of use.

DOI: http://dx.doi.org/10.5772/intechopen.89577

hearing progress with ongoing rehabilitation, if needed.

(this includes the family and supporting individuals).

7. Summary

Figure 5.

151

Stages of the rehabilitation process.

The input from any CI is inherently degraded compared to that available in normal-hearing individuals or, indeed, to those able to utilize a hearing aid effectively. Aging may play a role, slowing the process of learning [18] to accommodate to speech sounds presented as a new, seemingly unusual, set of sounds. Cognitive training should take into consideration the age of the CI user. In fact, it has been suggested that older CI users (>80 years) may benefit more from rehabilitation than younger users. A top-down approach may be the most appropriate approach for the older population [18].

#### 5.3 Role of plasticity

It is unknown to what degree the brain reorganizes speech when confronted with hearing loss [24]. We studied the dynamics of reversed cross-modal plasticity by TEP brain imaging during speech tracking before and after CI at two time points [25]. Essentially, as a result of auditory sensory deprivation, regions in the brain associated with perceiving visual input are activated during speech communication. After implantation, neuroplasticity is demonstrated as the brain recruits more auditory networks during tests of speech recognition. Olds et al. [26] confirmed these findings using the functional near-infrared spectroscopy (fNIRS) imaging technique. They observed cortical reorganization and suggested that listening effort may be involved in the cortically activated regions. They used several speech recognition tests, including sentences, with the CI turned off and on. This may account for the activated regions seen in our study, although neither of the test intervals utilized direct auditory input. We speculate that during hearing deprivation, sensitivity to voice progressively decreases. Anderson and Kraus [20] refer to this as "deprivation-induced changes in auditory mapping." Once sound is reintroduced, the more visually focused cortical regions reassert into the voice-sensitive regions. This cross-modal reactivation shows the cooperation between visual and auditory cortex. Thus, a profound aim of active rehabilitation is to take advantage, and encourage, reverse plasticity to aid in restoring cortical preference to meaningful auditory signals. This need is also recognized by other authors [27].

## 6. Ongoing post-implant support, evaluations of progress, and hearing training: 6-month follow-up

Testing speech in noise takes place at 6 months. We have seen that the relationship between performance in quiet and in noise is highly correlated. The early performance in quiet is manifested in the 6-month scores (see Figure 1). Testing at a signal-to-noise ratio (SNR) of 10 dB creates a reasonable challenge and serves as a further indicator of who requires continued rehabilitation. We have observed that it is possible to identify CI users who have demonstrated early success or a steep learning curve. The remaining patients continue as poor users needing support and ongoing counseling to maintain their motivation. With continued exposure to auditory stimulation, they can be advised that still more progress is possible for them.

Increases continue even up to 3 years, but the incremental gain is much less that what is usually seen during the first 6 months of use.
