1 Supplemental Methods
2 Inclusion criteria for our study include both pre- and post-lingually deafened children
3 with severe to profound hearing loss (1, 3). Pre-lingually deafened children include those under
4 age five with deafness from cochlear nerve deficiency, cochlear aplasia or severe hypoplasia,
5 severe inner ear malformations, or post-meningitis ossification. In pre-lingually deafened
6 candidates with a cochlea that is present and patent with a normally appearing cochlear nerve,
7 our protocol requires lack of a significant benefit despite consistent use of a cochlear implant for
8
≥ 6 months (3). Post-lingually deafened candidates included in our study but not reported here
9 are those who demonstrate a lack of benefit from appropriate cochlear implantation without the
10 possibility for revision or contralateral implantation and previously have developed open set
11 speech perception and auditory-oral language skills. Major exclusion criteria include pre- or
12 post-linguistic children making progress with CI, MRI with normal cochlea/cochlear nerves,
13 NF2, surgical contraindications, intractable seizures or neurological disorders, inability to
14 participate in device programing, and lack of potential for spoken language (1, 3).
15 Pre-operative imaging in all enrolled patients includes MRI with axial and sagittal
16 unenhanced T1-weight images, axial T2-weighted images, and axial FLAIR images through the
17 entire brain as well as high resolution 3D CISS images through the temporal bone (3). High
18 resolution temporal bone CT scans are also performed to generate contiguous axial and coronal
19 images where were acquired through the temporal bones at a thickness of 0.6 or 0.75 mm (3).
20 Post-operatively, patients are seen 1-2 weeks after surgery to confirm adequate healing.
21 At 4-6 weeks post-operatively, the ABI device is activated and programmed (3). For younger
22 patients, activation takes place over two days with a dedicated pediatric anesthesiologist present
23 within the audiologic test booth. On the initial day of activation, Precedex (dexmedetomidine
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24 hydrochloride) is administered to induce general anesthesia and carefully titrated throughout the
25 activation process. After the successful induction of anesthesia, each electrode is tested
26 individually with current increased in a step-wise manner. Higher currents may be associated
27 with a gag reflex, and these current limits are noted during testing. In addition, activation of
28 certain electrodes may trigger bradycardia, which is carefully monitored and corrected. These
29 electrodes are subsequently turned off to ensure there is no aberrant stimulation of the vagus
30 nerve with device use. After this initial programming, the patient returns the following day for
31 formal activation of the device while awake. Again, a pediatric anesthesiologist is present for the
32 procedure. A programming algorithm is utilized to optimize electrode activation. In particular,
33 each electrode is tested for audiologic response and any aberrant stimulation of other cranial
34 nerves or non-auditory sensations is noted. Both bipolar and monopolar stimulation are tested to
35 provide optimal auditory responses.
36 Follow-up thereafter occurs at regular 3 month intervals (3). In addition to regular clinical
37 follow-up, the ABI device is tested and reprogrammed as necessary. Post-operative evaluation
38 includes behavioral and audiometric testing with developmentally appropriate measures of
39 speech perception and language. Several age-appropriate questionnaires including the PedsQL
40 and a study-specific complications questionnaire are also administered.
41
42 Supplemental Discussion
43 Traditionally, ABI surgery is performed using a translabyrinthine craniotomy, which
44 provides access to the lateral recess of the fourth ventricle and the cochlear nucleus. This
45 approach provides a wide field view of the cochlear nerve and lateral recess, thereby minimizing
46 the risk of unintended facial nerve injury (4). However, insertion of the ABI electrode occurs in a
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47 blind manner, with intraoperative evoked potentials used to confirm positioning. In addition, this
48 approach is irreversible because the cochlea is destroyed. As a result of these limitations, the vast
49 majority of pediatric ABIs have been done using a retrosigmoid craniotomy. This approach
50 provides more direct access to the lateral recess with better visualization of lower cranial nerves.
51 In addition, the retrosigmoid approach reduces bleeding and operative time, avoids the need for
52 abdominal fat harvest, and reduces the risk of contaminating the wound with microorganisms
53 from the mastoid cavity (4). Consistent with these theoretical advantages, the most recent
54 European consensus statement on ABI surgery in non-NF2 pediatric patients calls for placement
55 of ABI devices using the retrosigmoid approach (5). Indeed, several groups internationally have
56 reported on their success with ABI surgery using a retrosigmoid craniotomy in non-NF2
57 pediatric patients (6-7). In our case, we successfully placed the ABI electrode array using a
58 retrosigmoid craniotomy with no complications such as CSF leak, wound infection, or device
59 extrusion, suggesting that this technique is effective for ABI placement in young children.
60 However, additional studies on a broad range of patients, especially infants, are needed to more
61 completely reinforce this conclusion.
62 Although international experience is more variable, our FDA approved clinical trial has
63 strict inclusion criteria which limit the participation of many potential pediatric candidates in our
64 study (1, 3). In the group of children below the age of five, the vast majority are pre-lingually
65 deafened patients who suffer from cochlear nerve deficiency, cochlear aplasia or severe
66
67 hypoplasia, severe inner ear malformations, or post-meningitis ossification. Our inclusion criteria call for attempted CI with no significant benefit for ≥ 6 months in patients with a cochlea that is
68 present and patent with a normally appearing cochlear nerve. This latter criterion is somewhat
69 controversial. Internationally, many centers are proceeding with ABI surgery in the absence of
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70 attempted CI if there is a well-defined congenital indication such as complete labyrinthine
71 aplasia, cochlear aplasia, cochlear nerve aplasia, or cochlear aperture aplasia, with attempted CI
72 reserved for patients with partial or incomplete cochlear or cochlear nerve malformations (5).
73 This urge to perform early ABI surgery and forego attempted CI is driven by a desire to leverage
74 greater cortical plasticity at a younger age, while avoiding the added challenges and risks of
75 surgery in a smaller child. Based on these cost/benefit analyses, most centers have identified the
76 optimal age for ABI surgery as 18 to 24 months, although implantation as early as 12 months of
77 age may be appropriate (1, 5). However, several recent studies suggest that attempted cochlear
78 implantation in the absence of radiologic evidence of a cochlear nerve may still be effective. For
79 example, a recent retrospective analysis of ten children with radiographic evidence of cochlear
80 nerve hypoplasia or aplasia revealed that imaging findings did not correlate with outcomes and
81 were a poor predictor of cochlear implant success (8). This controversy emphasizes a need for
82 better defining criteria for CI prior to ABI surgery versus proceeding directly to ABI in
83 circumstances where the benefit from CI may be limited.
84 International outcomes with pediatric ABI surgery are promising. For example, based on
85 the experience of the University of Verona with 24 children who underwent ABI surgery, all
86 children regularly used their devices, with many showing eventual improved communication and
87 attention at school and home (9-10). While open set speech recognition was rare, nearly all
88 patients achieved environmental sound awareness and lip-reading enhancement with some
89 obtaining multi-syllabic word recognition (9-10). Similar results were reported at Hacettepe
90 University where two of 11 implanted children achieved open set speech perception (6). Perhaps
91 the most impressive outcome involves a child with cochlear nerve aplasia who was implanted at
92 the University of Verona and subsequently followed at the House Ear Institute and the University
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93 of North Carolina (1, 11). By age three, this child was able to identify speech patterns
94 consistently with the emergence of closed-set word (11). He scored 100% on an ESP
95 monosyllabic word test and an evaluation by speech pathology suggested the use of functional
96 spoken language (1).
97 The importance of hearing rehabilitation extends beyond functional benefits to also
98 influence quality of life. For example, retrospective population studies have suggested that the
99 cost of hearing loss may be over $1 million dollars per child over their lifetime, while other
100 analyses indicate that hearing loss may be associated with depression and anxiety (1, 11-13).
101 Thus, the financial and personal costs of severe to profound hearing loss are substantial.
102 Fortunately, hearing rehabilitation may help to mitigate gaps related to hearing loss. In our
103 patient, for example, there were improvements in physical symptoms as well as emotional
104 functioning following ABI surgery based on the PedsQL, a validated inventory of health-related
105 quality of life measures in the pediatric population (15). Although other categories of physical
106 and psychosocial function were largely unchanged following ABI surgery, improvement in these
107 other areas may be better appreciated with more long-term use of the ABI device. Future studies
108 of ABI surgery should focus on improvements in quality of life alongside the benefits of hearing
109 rehabilitation, with more substantial analyses to help validate our initial observations.
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Supplemental References
1.
Buchman CA, Ewend MG, Teagle HFB, et al. “An early feasibility study of the safety and efficacy of the Nucleus 24 auditory brainstem implant in children with cochlear or cochlear nerve disorders not resulting from neurofibromatosis type II.” ClinicalTrials.gov Identifier:
NCT01904448, FDA approval August 10, 2012.
2.
Buchman CA, Ewend MG, Teagle HFB, et al. “Auditory brainstem implantation in young children.” 13th international conference on cochlear implants and other implantable auditory technologies, Munich, Germany, June 18-21, 2014.
3.
Puram SV, Herrmann BS, Lee DJ. “Auditory brainstem implant (ABI) in pediatric nonneurofibromatosis type 2 subjects.” ClinicalTrials.gov Identifier: NCT01864291, FDA approval May 2013.
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Lin HW, Herrmann BS, Lee DJ. Cochlear Implants and Other Implantable Hearing Devices.
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Sennaroglu L, Colletti V, Manrique M, et al. Auditory brainstem implantation in children and non-neurofibromatosis type 2 patients: a consensus statement. Otol Neurotol.
2011;
32(2):187-91.
6.
Sennaroglu L, Ziyal I, Atas A, et al. Preliminary results of auditory brainstem implantation in prelingually deaf children with inner ear malformations including severe stenosis of the cochlear aperture and aplasia of the cochlear nerve. Otol Neurotol.
2009; 30(6):708-15.
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Colletti L, Wilkinson EP, Colletti V. Auditory brainstem implantation after unsuccessful cochlear implantation of children with clinical diagnosis of cochlear nerve deficiency. Ann
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8.
Young NM, Kim FM, Ryan ME, et al. Pediatric cochlear implantation of children with eighth nerve deficiency. Int J Pediatr Otorhinolaryngol.
2012; 76(10):1442-8.
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9.
Colletti L, Zoccante L. Nonverbal cognitive abilities and auditory performance in children fitted with auditory brainstem implants: preliminary report. Laryngoscope 2008;
118(8):1443-8.
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Colletti L. Beneficial auditory and cognitive effects of auditory brainstem implantation in children. Acta Otolaryngol . 2007; 127(9):943-6.
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Eisenberg LS, Johnson KC, Martinez AS, et al. Comprehensive evaluation of a child with an auditory brainstem implant. Otol Neurotol.
2008; 29(2):251-7.
12.
Garland MH. Depression and dementia. Hospital Update 1978; 313-319.
13.
Herbst KG, Humphrey C. Hearing impairment and mental state in the elderly living at home.
British Medical Journal 1980; 281:903-905.
14.
Wolman J. Refunded CSEF to conduct new national study of special education expenditures.
The CSEF resource 1999.
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Varni JW, Seid M, Rode CA. The PedsQL: measurement model for the pediatric quality of life inventory. Med Care.
1999; 37(2):126-39.
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