Auditory Brainstem Implantation in Children

Abstract

Until last decade, use of auditory brainstem implant (ABI) was restricted to adults and children with severe inner ear malformations and cochlear nerve aplasia did not have any option for hearing rehabilitation. Use of ABI opened a new era for this group of patients. In this review article, definite and probable indications of ABI for children are stated. Among probable indications, children with hypoplastic nerves constitute the most challenging group in decision making between cochlear implant (CI) and ABI. In these patients, radiological findings should be utilized together with preoperative and intraoperative audiological evaluation. However, none of these assessment methods offer enough data to enable correct choice between CI and ABI. Intracochlear electrical ABR (eABR) seems to a better indicator compared to preoperative electrophysiological tests. Commonly, CI is the first choice in these patients; if benefit with CI is not satisfactory during follow up, then ABI is utilized. Further definitive diagnostic tools are require in order to overcome this uncertainty. The ABI team must be experienced on pediatric CI patients, also an experienced pediatric neurosurgeon is indispensable to achieve success and to avoid complications. Age limit for ABI is similar to CI candidate children. Better language outcome is expected at younger ages, i.e., between 1 and 2 years. Preoperative radiological work up involves both high resolution computed tomography and magnetic resonance imaging. The side with less severe inner ear malformation or with more developed neural structures can be preferred. In preoperative audiological evaluation, subjective tests should always be included in test battery as well as objective ones. Rehabilitative assessment is focused on auditory perception skills, language and speech skills and learning abilities. Surgical method of choice is retrosigmoid approach in children. Intraoperative eABR measurements are important to determine correct position of electrode. Interindividual variability in language development and audiological outcome is prominent. Overall complication rate is in an acceptable range when surgery is performed with an experienced team. In conclusion, ABI can provide satisfactory audiological outcomes and language development to a certain extent is possible when every aspect of whole process is applied properly.

Bimodal stimulation in children with inner ear malformation: One side cochlear implant and contralateral auditory brainstem implant

“…Cochlear hypoplasia with hypoplastic cochlear aperture, the presence of an unbranched CVN and hypoplastic CN constitute a dilemma for decision‐making for CI and ABI selection . Previous studies report poor outcomes for IEMs with CN deficiency with CI .…”

“…Patients with hypoplastic CNs or thin, unbranched CVNs constitute the most controversial group in the CI and ABI decision . Even in patients with confirmed CN hypoplasia or aplasia on magnetic resonance imaging (MRI), some auditory responses could be observed on certain frequencies during audiological evaluation in one or both ears, which is compatible with severe hearing loss . Cochlear implant users with hypoplastic CN or CVN have only a limited benefit and lag behind the cochlear implant users with normal CN or CVN .…”

“…Even in patients with confirmed CN hypoplasia or aplasia on magnetic resonance imaging (MRI), some auditory responses could be observed on certain frequencies during audiological evaluation in one or both ears, which is compatible with severe hearing loss . Cochlear implant users with hypoplastic CN or CVN have only a limited benefit and lag behind the cochlear implant users with normal CN or CVN . Another amplification option for these types of patients is the ABI, which improves environmental sound awareness, speech detection and language skills .…”

Recent Rehabilitation Experience with Pediatric ABI Users

“…Auditory spoken language development was categorized with MSLDS and focused on charting their progress over time [7] . Also, we evaluated the speech intelligibility of children with speech intelligibility rating (SIR) [8] . It has five performance categories ranging from "pre-recognizable words in spoken language" to "connected speech are intelligible to all listeners.…”

Regulatory and Funding Strategies to Develop a Safety Study of an Auditory Brainstem Implant in Young Children Who Are Deaf

“…Worldwide, with nearly 15 years of experience with the ABI in pediatric patients, the ABI is an accepted treatment option [8, 14–17]. A path forward for US FDA approval is less clear.…”