Abstract

Rehabilitation for any cochlear implant (CI) recipient is a process having the aim of taking the necessary steps to enable users to achieve their best possible auditory outcome. It involves all stages of interaction including evaluations for candidacy, device selection, preoperative counseling, surgical intervention, device activation, post-implant support, evaluations of progress, and hearing training. Since rehabilitation is an ongoing process, it becomes critical to determine what is sufficient, that is, how intense the follow-up program must be, especially since there is substantial variability for results on outcome measures that assess progress in hearing function and abilities after implantation.

Keywords: rehabilitation, cochlear implant

#### 1. Introduction

Rehabilitation for any cochlear implant (CI) recipient is a process having the aim of taking the necessary steps to enable users to achieve their best possible auditory outcome. It involves all stages of interaction including evaluations for candidacy, device selection, preoperative counseling, surgical intervention, device activation, post-implant support, evaluations of progress, and hearing training. Since rehabilitation is an ongoing process, it becomes critical to determine what is sufficient, that is, how intense the follow-up program must be, especially since there is substantial variability for results on outcome measures that assess progress in hearing function and abilities after implantation [4].

A primary aspect of our rehabilitation approach is early identification of the challenges associated with the remediation of adult cochlear implant users who demonstrate poor results on objective measures. A poor performer may be described as one who achieves " … limited performance after taking in account the preoperative biographic factors during counselling the patient and anatomical factors electrode insertion" [1].

The approach we present in this chapter is based on years of experience and research in our facility and in cooperation with other multicenter studies. Nearly 50% of our patient population will be managed, postoperatively, through conventional (passive) auditory rehabilitation, which means managing all aspects related to device use and counseling and encouraging patient-driven practices. Patientdriven practices take advantage of everyday life encounters, whether it be through exposure to TV and videos/movies without captioning, audiobooks, telephone use, social media communication applications (Skype, FaceTime, WhatsApp, etc.), family encounters at group get-togethers, one-on-one with co-workers or friends and family, etc. [2]. The remaining patients will require further, detailed investigations and personalized active rehabilitation. Experience shows that the early identification of those requiring more active rehabilitation training leads to better outcomes. It results in a reduction in the number of visits for those requiring less direct intervention and allows our clinical specialists to concentrate on improving the outcomes of poorer performers.

## 2. Preoperative counseling

Although candidates receive comprehensive counseling throughout their rehabilitation program, the pre-implant sessions lay the foundation for establishing realistic expectations. This goal is supported by employing a predictive model from which the basis for expectations can be established. The model predicts the sentence recognition score of CI users 1 month after activation. It was derived and simplified from the analysis by [1]. The model takes into consideration only the duration of severe-to-profound hearing loss (HL) and one key etiology, congenital hearing loss, which produced significantly lower scores than other etiologies (including "unknown" causes). The formula is easily applied:

$$\text{Predicted score} = \text{90} - \text{0.5} \times \text{years } \text{H} \text{L} - \text{50 (if } \text{congenital } \text{H} \text{L)} \tag{1}$$

score at 70. If the result of the prediction is less than 70, the expectation is that the new user will require active rehabilitation in addition to the conventional recom-

Distribution of sentence recognition scores assuming correct electrode array position (raw scores) and, in addition, removing the effects of duration of deafness and etiology (corrected scores). Number labels represent percentiles for the population. The raw score distribution helps us in preoperative counseling; the corrected scores

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

The information gained from the model helps in setting realistic expectations during pre-implant counseling and in early planning by clinical specialists for potential rehabilitation needs. One could be advised that the challenges of adapting to the new sensations may be slow, requiring many visits not only for device fitting but also for direct practice. On the other hand, others might be advised that they may experience a rapid adaptation and likely understand most of what people say if listening in quiet circumstances. Early advice about whether to expect slow or rapid progress can also serve as a motivational tool. If new CI listeners understand how involved they will need to be once their CI is activated, they can be motivated to engage in listening activities as opposed to simply expecting to be fixed. Motivation has a significant impact on adult learning [3]. It may first be established by setting

During pre-implant counseling, patients are advised that there are many factors that influence results and that these will be discovered systematically beginning at the first activation of the device and at the first-month evaluations. Indeed,

although patient outcomes may turn out quite differently than expected, given that not all influencing factors can be known and that each CI user is unique, early, realistic expectations establish the foundation for accepting new sound sensations. Our research has shown that the main factors that influence performance are related to circumstances of etiology and duration of deafness, outcomes of surgical intervention of insertion depth and dislocation, and central aspects of linguistic and neurocognitive skills [1]. The variability seen in speech recognition scores are

mendations of patient-directed listening activities.

help us in remediation 1-month post-activation.

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

appropriate expectations.

Figure 1.

described in Tables 1 and 2.

143

where 90 represents the expected score (out of one hundred) for a good performer, which is reduced by 0.5 points per year of severe-to-profound hearing loss and further reduced by 50 points if the etiology was congenital HL. If the etiology is not congenital, then the formula is only 90 minus half the number of years of HL. The predictive model is not valid for cases of labyrinthitis (e.g., chronic otitis and autoimmune disease), where the findings of [1] indicated considerable variability and generally poor outcomes. Our evidence from adults suggests a priori that those with congenital HL are expected to yield poor performance scores. As an example, for deafness acquired in adulthood for a duration of 40 years, the prediction would be a score of 70; however, if the deafness had been congenital, the score would be 20. Another example for a person with short-term deafness of 6 years would yield a higher score (90 � 3 = 87). The predictions are valid assuming that the best surgical outcome is obtained in terms of electrode array position and insertion depth (see below).

As will be discussed later, outcome scores could be worse than expected for any CI user and would indicate the need for ongoing rehabilitation intervention. Individuals with poorer than expected scores would be considered poor users. In other words, additional factors may intervene with the duration of deafness and etiology to affect the results, many of which can be investigated and evaluated only after implantation.

Based on the population data from [1], we generated a distribution of scores assuming ideal electrode position before activation, that is, no dislocation and insertion depth within the recommended limits. The resultant median score was at approximately 70/100 (Figure 1, raw scores, left).

If there is to be some effect on the overall population performance, we need to choose a relatively high threshold below which we will apply active rehabilitation. The rationale is that bringing up the performance of the lowest half of the population is a worthy, and likely, achievable aim, and, therefore, we set the threshold

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

Figure 1.

exposure to TV and videos/movies without captioning, audiobooks, telephone use, social media communication applications (Skype, FaceTime, WhatsApp, etc.), family encounters at group get-togethers, one-on-one with co-workers or friends and family, etc. [2]. The remaining patients will require further, detailed investigations and personalized active rehabilitation. Experience shows that the early identi-

Although candidates receive comprehensive counseling throughout their rehabilitation program, the pre-implant sessions lay the foundation for establishing realistic expectations. This goal is supported by employing a predictive model from which the basis for expectations can be established. The model predicts the sentence recognition score of CI users 1 month after activation. It was derived and simplified from the analysis by [1]. The model takes into consideration only the duration of severe-to-profound hearing loss (HL) and one key etiology, congenital hearing loss,

Predicted score ¼ 90 � 0:5 � years HL � 50 if congenital HL ð Þ (1)

As will be discussed later, outcome scores could be worse than expected for any CI user and would indicate the need for ongoing rehabilitation intervention. Individuals with poorer than expected scores would be considered poor users. In other words, additional factors may intervene with the duration of deafness and etiology to affect the results, many of which can be investigated and evaluated only after

Based on the population data from [1], we generated a distribution of scores assuming ideal electrode position before activation, that is, no dislocation and insertion depth within the recommended limits. The resultant median score was at

If there is to be some effect on the overall population performance, we need to choose a relatively high threshold below which we will apply active rehabilitation. The rationale is that bringing up the performance of the lowest half of the population is a worthy, and likely, achievable aim, and, therefore, we set the threshold

fication of those requiring more active rehabilitation training leads to better outcomes. It results in a reduction in the number of visits for those requiring less direct intervention and allows our clinical specialists to concentrate on improving

which produced significantly lower scores than other etiologies (including

where 90 represents the expected score (out of one hundred) for a good performer, which is reduced by 0.5 points per year of severe-to-profound hearing loss and further reduced by 50 points if the etiology was congenital HL. If the etiology is not congenital, then the formula is only 90 minus half the number of years of HL. The predictive model is not valid for cases of labyrinthitis (e.g., chronic otitis and autoimmune disease), where the findings of [1] indicated considerable variability and generally poor outcomes. Our evidence from adults suggests a priori that those with congenital HL are expected to yield poor performance scores. As an example, for deafness acquired in adulthood for a duration of 40 years, the prediction would be a score of 70; however, if the deafness had been congenital, the score would be 20. Another example for a person with short-term deafness of 6 years would yield a higher score (90 � 3 = 87). The predictions are valid assuming that the best surgical outcome is obtained in terms of electrode array position and insertion

"unknown" causes). The formula is easily applied:

approximately 70/100 (Figure 1, raw scores, left).

the outcomes of poorer performers.

Advances in Rehabilitation of Hearing Loss

2. Preoperative counseling

depth (see below).

implantation.

142

Distribution of sentence recognition scores assuming correct electrode array position (raw scores) and, in addition, removing the effects of duration of deafness and etiology (corrected scores). Number labels represent percentiles for the population. The raw score distribution helps us in preoperative counseling; the corrected scores help us in remediation 1-month post-activation.

score at 70. If the result of the prediction is less than 70, the expectation is that the new user will require active rehabilitation in addition to the conventional recommendations of patient-directed listening activities.

The information gained from the model helps in setting realistic expectations during pre-implant counseling and in early planning by clinical specialists for potential rehabilitation needs. One could be advised that the challenges of adapting to the new sensations may be slow, requiring many visits not only for device fitting but also for direct practice. On the other hand, others might be advised that they may experience a rapid adaptation and likely understand most of what people say if listening in quiet circumstances. Early advice about whether to expect slow or rapid progress can also serve as a motivational tool. If new CI listeners understand how involved they will need to be once their CI is activated, they can be motivated to engage in listening activities as opposed to simply expecting to be fixed. Motivation has a significant impact on adult learning [3]. It may first be established by setting appropriate expectations.

During pre-implant counseling, patients are advised that there are many factors that influence results and that these will be discovered systematically beginning at the first activation of the device and at the first-month evaluations. Indeed, although patient outcomes may turn out quite differently than expected, given that not all influencing factors can be known and that each CI user is unique, early, realistic expectations establish the foundation for accepting new sound sensations.

Our research has shown that the main factors that influence performance are related to circumstances of etiology and duration of deafness, outcomes of surgical intervention of insertion depth and dislocation, and central aspects of linguistic and neurocognitive skills [1]. The variability seen in speech recognition scores are described in Tables 1 and 2.


surgical intervention each play a role in performance outcomes and account for

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

Preoperatively, it is essential to choose the appropriate electrode type and to target an insertion depth of one cochlear turn (i.e., 360°) as proposed by [1]. This aim is also supported by [9], who indicated a negative correlation between word scores and electrode insertion depth measures. The study by Lazard et al. [6] also found poorer outcomes for the most deeply inserted electrodes. These results need to be tempered against the potential of having larger frequency-place mismatches for shallower electrode insertion depths as discussed in the following

Any information that contributes to the first activation and mapping for listening programs is useful. The insertion depth provides a reference for better accessing appropriate frequency allocations relative to cochlear tonotopic organization [8]. Electrode design also plays a role not only because of its insertion characteristics, straight or curved, but also because of the spacing between contact electrodes. Our studies have shown that an insertion depth of 300–360° yielded optimal performance. Moderate shifts in frequency-to-place may easily be accommodated by the listener, but larger shifts >1.5 octave may affect auditory performance, and adaptation may take longer [10]. Electrode placement can be detected by routine intraoperative X-ray. Shifts were approximately one octave for Nucleus Implants with 360° insertion depth, with shifts still <1.5 octaves for 300°, for the default frequency allocation table. For other devices, the shifts appeared greater for the same insertion depths due to the specific default frequency-to-electrode allocation used in the device. Thus, these devices may work most effectively with greater insertion depths or, alternatively, with the use of customized frequency allocation

Avoiding a frequency-place shift of greater than 1.5 octaves will probably produce the best result for a given insertion depth. However, further optimization may be achieved by limiting insertion depth at surgery or deactivating the most apical electrodes (e.g., [11]). If electrode arrays are found to be inserted greater than one turn, we may consider deactivating the most apical electrode contacts to simulate the ideal insertion depth. This is consistent with the work of [8] whose temporal bone studies found correlations between specific insertion depth angles and tonotopic frequency locations. Deeper insertion, greater than 360°, was associated with frequencies lower than 900 Hz; however, one needs to consider that the spatial density of spiral ganglion cells increases considerably past this point, such that cross-turn stimulation can easily occur. As mentioned, depending on the device type, if the active insertion depth is limited to 360°, then it may be necessary to modify the frequency-to-electrode allocation through programming to avoid exces-

After the electrode has successfully been placed into the cochlea, monitoring its position is accomplished through intraoperative X-ray [7]. The neural activity of device-activated electrical stimulation is evaluated with neural response telemetry (NRT), which replicates electrically evoked compound action potentials (ECAP). The NRT responses provide an objective measure of the integrity of auditory nerve function when stimulated through a CI [12, 13]. It can be administered intra- and postoperatively; a thorough description of the method is described by [14], and the newer application of auto-NRT is described by [15]. Intraoperatively, the focus is on gaining details relating to whether the device is operational and whether the responses per electrode indicate that electrodes are within the scala tympani and

tables that can be adjusted in the specific programming software.

8–13% of the variance in performance scores at 1 year.

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

section.

sive frequency-place shifts.

3.1 Intraoperative tests

145

Table 1.

Patient history factors explaining significant variance (\*) at 1-month post-activation with respect to outcomes of sentence recognition.


Table 2.

Surgical factors explaining significant variance (\*) at 1-month post-activation with respect to outcomes of sentence recognition.

#### 2.1 Main factors influencing performance

A thorough patient history is needed to gain details of etiology and duration of hearing loss. Our studies indicate that 6–12% of the total variance for speech understanding in quiet is related to the duration of deafness and approximately 30% is related to the etiology [1]. For instance, congenital HL produces significantly poorer scores in the short term and chronic otitis media in the long term [1, 4]. Certain diseases may produce greater damage to the cochlea resulting in poorer signal transmission after implantation such as bony tissue growth induced by meningitis or trauma. Speech signals may be distorted more than expected by poor neural representation of speech features due to anatomical distortions from diseases that affected the hearing [5]. The challenge is that characteristics of even a known etiology may not be clear.

Details concerning the duration of deafness may be elusive; for instance, defining the specific onset of significant hearing loss may be difficult to determine and impacted by hearing aid use (i.e., how much was one or two hearing aids actually used (e.g., [6]), was the loss progressive, how rapid did the loss develop, and so forth). The impact of unanswered questions may be seen in later performance, especially in cases of unexpected poor performance. Applying the predictive model helps estimate potential outcomes.
