This chapter reports the audiological outcome of pediatric auditory brainstem implantation (ABI) in Hacettepe University. Our preliminary ABI outcome was reported in 2009 and minimum patient age was 2.5 years at that time. In that report six children gained basic audiological functions. In 2016, we reported long-term ABI outcome where the minimum age was lowered to 1 year. Majority of the children had Categories of Auditory Performance (CAP) score of 5. Children with better thresholds were in categories 6, 7, and 8. Speech intelligibility scores were also better in children with lower thresholds. Children with common cavity performed better when compared to other inner ear malformation groups. In a most recent outcome of 84 pediatric ABI users who used their device for more than 1 year, 52% demonstrated 100% pattern recognition in words (closed-set condition), 24% demonstrated 100% word identification (closed-set condition), and 15% of them repeated more than half of the open-set sentences correctly in auditory-only condition.
14 Outcomes in Pediatric ABI: The Hacettepe University Experience
14.1 Brief History of ABI Experience in Hacettepe University
The first auditory brainstem implant (ABI) in Turkey was performed in Hacettepe University in 2002 after removal of a vestibular schwannoma in a postlingually deafened NF2 patient. In 2005, another NF2 patient received an ABI in our department. In 2006, we started ABI in prelingually deafened children. In July 2006, we performed three cases and our team waited to see initial audiological outcome before continuing the procedure. At the initial programming, all three children demonstrated response to sound. After observing their performance, our team continued with ABI surgery in children. Between June 2006 and January 2018, our team performed 116 primary and 5 revision pediatric ABIs.
14.2 Preliminary Results of Pediatric ABI
In 2009, our team published preliminary results of pediatric ABI cases. 1 This paper reported the results of the first 11 children who received an ABI between 2006 and 2008. They were all operated via retrosigmoid approach, always together with a neurosurgeon. Their ages were between 2.5 and 5 years. During initial programming, all patients demonstrated some nonauditory side effects. Some of the nonauditory stimulation were due to high stimulation level, besides acoustic stimulation. In these patients, current level was decreased until the patient could hear without any nonauditory side effect. The second group did not have any acoustical stimulation, but had only nonauditory side effects in some channels. In the latter group, the channel producing the side effects was turned off.
Six children achieved basic audiologic functions and were able to recognize and discriminate sounds, and many could identify environmental sounds such as a doorbell and telephone ring by the third month of ABI use.
Six of the patients demonstrated increase in the number of active channels between initial and follow-up programming. Their dynamic range also increased. Dynamic range increase is also related to better stimulability of the cochlear nuclei over time. This was interpreted as a kind of adaptation over time in the surrounding neural structures related to side effects.
Two children had additional handicaps. Additional handicaps slowed the progress of these children compared to other patients with cochlear implantation. The patients with attention deficit hyperactivity disorder were among the worst in terms of subjective auditory performances. Despite lack of open-set scores in children with additional disabilities, their parents reported that they feel much more confident in their educational settings and in their family.
14.3 Long-Term Results of ABI
In 2016, we published long-term results of pediatric ABI in Hacettepe University. Between 2006 and 2014, 60 children received ABI in Hacettepe University. 2 There were 35 children who had used ABI for at least 1 year. Among the radiological indications, complete labyrinthine aplasia, cochlear aplasia, common cavity, incomplete partition I, cochlear hypoplasia, and cochlear nerve aplasia were present.
Size of the ABI electrode was suitable for lateral recess. Only in two cases, foramen of Luschka had to be enlarged slightly. They were very young children operated at 1 year of age. There was no serious complication. Three children had transient facial paresis, which recovered completely in 2 weeks.
Categories of Auditory Performance (CAP) scores were assessed according to hearing thresholds. Children were separated into three groups according to their hearing thresholds: Group I: 25–40 dB, Group II: 41–50 dB, and Group III: ≥50 dB. Majority of the children had CAP score of 5. This means that they could understand common phrases without lipreading. In Group I, with better thresholds, certain patients were in categories 6, 7, and 8. Patients with such high scores were not present in groups with higher thresholds (Groups II and III). Similar finding was also present in Speech Intelligibility Rating (SIR) scores. Group I had better SIR scores than Groups II and III. Therefore, hearing thresholds are very important in auditory performance and speech intelligibility, where better CAP and SIR scores were observed with lower thresholds.
Functional auditory performance of cochlear implant (FAPCI) scores revealed that children with an ABI were in the lowest 10 percentile. This shows that language outcomes of ABI in children with severe inner ear malformations in general are not as good as cochlear implant (CI) users with normal anatomy.
Relationship of hearing threshold with language acquisition was also assessed. With lower thresholds, it is possible to obtain better language development.
The relationship of the number of active electrodes and the hearing thresholds was also investigated. For standardization, the number of active electrodes was defined as a percentage of the total number of electrodes. No relationship between the number of active electrodes and the hearing thresholds or language outcome was present.
Interesting findings were present in the type of inner ear malformation. Among the radiological classification, best performance was in the group “common cavity.” In addition, the patients were separated into two groups according to the presence of cochlea vestibular nerve (CVN): “CVN present” (inner ear malformations such as common cavity) and “CVN absent” (complete labyrinthine aplasia etc.). Auditory performance was better in children with common cavity, or CVN present, and showed statistically significant difference. In common cavity, there is some cochlear neural tissue both in the cavity and in the CVN coming from the cavity. This may be the reason for better performance of this particular anomaly group in all test methods versus other etiologies.
When cognitive skills were taken into consideration, this also had a significant impact on the outcome. Group with impaired intelligence showed worse outcome in auditory performance, speech intelligibility, and language acquisition. As mentioned in preliminary results, attention deficit hyperactivity disorder, visual impairment, and mental retardation, combined as a group of handicap, negatively influenced SIR, CAP, and Manchester test scores.
Eighteen children had 100% pattern discrimination and the remaining 11 patients had scores between 33 and 96%. In multisyllabic words, 11 patients scored 100% and 8 patients scored between 25 and 92%. Among 35 children, 12 had open-set scores above 50%, 2 had 100%, and 10 patients scored above 50%. There was no correlation between number of active electrodes and closed- and open-set perception scores. On the other hand, hearing thresholds were inversely moderately correlated with closed- and open-set scores. In general, children demonstrated very good progress in the first 2 years but then the progress slowed down but continued at a slower pace.
14.3.1 Most Recent Audiological and Language Outcome of 84 Patients with ABI
Between June 2006 and January 2018, 116 children with complex inner ear malformations received an ABI by Hacettepe Implant team. Five of these were revision due to device failure. The results of 84 primary pediatric ABI patients who have been using their ABI for more than a year were analyzed and recently presented at European Pediatric Cochlear Implantation Meeting in Lisbon. 3 Of the total number of patients, 64% were female and 36% were male. Auditory verbal communication mode is used by 70% of these children and the rest have chosen total communication.
Auditory perception skills were evaluated by using Meaningful Auditory Integration Scale (MAIS) 4 and Categories of Auditory Performance (CAP-II). 5 Closed-set pattern perception subtest, closed-set word identification subtest, and open-set sentence recognition subtest were used from Children Auditory Perception Test Battery in Turkish. 6 Language performance was assessed with Test of Early Language Development (TELD-3) 7 and SIR. 8
When we examined the relationship between duration of ABI use and progress of CAP scores, at the end of 6 months, it was observed that detection of environmental sounds obviously developed. By the first year of ABI use, they were able recognize most of the environmental sounds and their sources. One year later, most of the children were able to reach the “Discrimination of speech sounds without lipreading” (CAP-II) and “Understanding of common phrases without lipreading” (CAP-III) levels (Fig. 14.1). It was noted that patients usually stayed at this level for a long period as it is more difficult to move to the next level. This is because the next level requires complex linguistic and cognitive skills, more than identifying daily words and sentences. By the end of third year of ABI use, they achieved their best performance on auditory perception skills. However, we should always keep in mind that their auditory perception skills continue to develop in different rates. It was also noted that in our study, children who were implanted at younger age (< 3 years old) showed faster progress and achieved higher scores in terms of auditory perception skills (Fig. 14.2). As a final comment, substantial number of patients (25/30) were able to follow the conversation without lipreading or speech reading cues. Despite the small number of children (only 5/30 children) who could reach the final stage, it was promising that some of them were able to carry out conversation even by telephone.
We also used CIAT (Test for Auditory Perception Skills for Children in Turkish) battery in order to evaluate their speech perception skills. 2 In closed-set condition, 52% demonstrated 100% pattern recognition in words, while 24% showed pattern recognition of 50 to 100% (Fig. 14.3). In word identification in closed-set condition using ABI only, 24% demonstrated 100% identification, while 36% identified 50 to 100% of the words presented (Fig. 14.4). Approximately 15% of them repeated more than half of the open-set sentences correctly in auditory-only condition. Sentence recognition of 20 to 50% was demonstrated by 21%.
We have also evaluated the language performance of the children by considering their receptive and expressive language skills. Although we collect the data by observing their communication performance in daily situations, we also rely on language performance test scores. However, comparing the gap between their chronological ages and language equivalent scores do not provide realistic scores as their hearing ages starts with ABI activation. So considering the gap only may not provide the correct results. Depending on the duration of the auditory deprivation, language development was estimated to be delayed. For this reason, we determined a linear increase considering the duration of implant use (Fig. 14.5). We also encounter similar process in expressive language development (Fig. 14.6). However, in expressive language development, the contents of the cues become more complicated and the words expected to be used are shifted to the plateau after a while due to the increase of the lengths of the speech sounds. Depending on the variables such as the enriched environmental stimulus surrounding the child, cognitive skills, educational status of the parents and/or caregiver, and the quality of rehabilitation program, the expressive language development may move to the next stage faster.
On the other hand, no statistical difference was obtained between the duration of ABI use and speech intelligibility according to the SIR classification. 8 However, as shown in Fig. 14.7, it can be observed that children who start using ABI at an early age were able to make faster progress and achieve higher scores in speech understanding than the ones who were implanted in older ages (< 3 years old). However, comprehension skills that also require the phonological resolution of vocalizations were observed as the most difficult task for children. Generally, they were in categories 2 and 3 in SIR. Their speech production can be defined as either “Connected speech is unintelligible” or “Connected speech is intelligible to a listener who concentrates and lip reads.”
In our patient population, 24% had at least one additional difficulty such as CHARGE, cerebral palsy, Goldenhar, or mental motor retardation. When cognitive performance was taken into consideration, it was determined that there was a significant difference between their speech comprehension skills, auditory perception scores, and language skills. Children who were good performers in terms of cognitive skills were also able to use auditory perception skills in daily circumstances (FAPCI), 9 and develop better language skills (Manchester language test) with a more intelligible speech interaction (SIR) (Table 14.1).