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Evaluation for pediatric auditory brainstem implant (ABI) candidacy includes a thorough neurotologic and neurosurgical consultation, audiologic evaluation including both behavioral and electrophysiologic testing, speech and language consultation, high-resolution temporal bone computed tomography and MRI imaging, and neuropsychological assessment of developmental milestones.
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Indications for an ABI in infants and children include bilateral cochlea aplasia/hypoplasia, cochlear nerve
Pediatric Auditory Brainstem Implant Surgery
Section snippets
Key points
Treatment goals and outcomes
The treatment goals for pediatric ABI surgery are (1) safe and successful placement of ABI electrode array through the foramen of Luschka (to bring electrode in close proximity to cochlear nucleus), (2) measurable electrically-evoked auditory brainstem responses (EABR) seen intraoperatively, (3) minimizing surgical complications such as CSF leak and facial nerve injury, (4) habilitation/rehabilitation of deafness with meaningful sound detection on behavioral testing, and (5) avoidance of side
Implant Systems
The ABI system is modular, with both external and internal components that capture, transduce, process, and propagate auditory stimuli into electrical signals to the electrode array, similar to that of the CI. The external components include a microphone, battery, speech processor, and transmitter coil. Acoustic stimuli are processed and transmitted as electronic signals to a receiver-stimulator via an induction coil. The surgically implanted receiver-stimulator then carries these signals to
Surgical approach
Choosing which side to implant is primarily based on anatomic considerations and evidence of any detectable thresholds on behavioral or electrophysiologic testing. If both ears demonstrate no functional hearing, then the side with the most accessible lateral recess and radiographic evidence of a cochlear nerve should be implanted. If both sides are similar audiologically and on radiology, the right ear is chosen based on the hypothesis that speech perception abilities rely more on left-brain
Postoperative management
All pediatric patients are monitored in a dedicated pediatric surgical intensive care unit after ABI surgery with hourly neurologic checks for the first 24 hours. A head CT is ordered on the evening of surgery to confirm stable electrode placement and absence of intracranial bleed or midline shift. Perioperative steroids can reduce edema and can be tapered over the patients’ inpatient admission. In our initial experience with 5 retrosigmoid craniotomies for ABI placement in children, the
Complications associated with pediatric abi surgery
Most of the studies looking at complication rates in ABI surgery have been completed in adults and in the context of vestibular schwannoma excision. Thus, we review these data here as dedicated studies of complications following pediatric surgery are limited. The translabyrinthine approach has been the primary approach for ABI surgery historically. Among 258 patients who underwent vestibular schwannoma resection over a 14-year period, perioperative complications included CSF leak (7.8%),
Recovery and auditory habilitation
As CSF leak is the most common complication seen following retrosigmoid craniotomy for ABI in children, a meticulous multilayer closure and use of firm pressure dressing for 5 to 7 days are crucial. Soft splints over the upper extremities are used to reduce displacement of the pressure dressing in the vigorous child. A formal face-lift wrap can be used to provide durable and stable placement of the mastoid dressing. Hospital stay following ABI surgery has ranged from 2 to 4 days for our first
Outcomes and clinical results in the literature
Dedicated pediatric ABI outcomes are not well described in the literature. Thus, we focus on ABI outcomes in both adults and children, which includes a summary of the few pediatric studies completed to date. ABI outcomes vary depending on the patient population, with nontumor patients typically achieving better outcomes than patients with NF2. ABI users with NF2 can expect auditory sensation, environmental sound awareness, and, occasionally, closed-set word recognition. Rarely, these patients
Future of auditory brainstem implant technology
As described in previous sections, the ABI provides meaningful auditory benefits to patients with severe to profound hearing loss; however, outcomes are highly variable across similar cohorts of patients.2, 27, 35 Further, many ABI users experience side effects, such as facial pain, involuntary motor movement, as well as dizziness, caused by activation of nonauditory neurons.6 A possible explanation for the wide range of audiometric outcomes and side effects may be the nonspecific spread of
Summary
Over the past several decades, there has been tremendous evolution in our understanding of auditory physiology and a deeper appreciation for the measures needed to improve hearing habilitation outcomes in deaf pediatric patients. Although CIs have become a mainstream option to improve hearing, this technology does not provide substantial benefits to individuals with profound hearing loss and small or absent inner ear anatomy. The ABI offers an alternative means of stimulating and activating
Acknowledgments
The authors would like to thank Elliott Kozin, MD and Aaron Remenschneider, MD, MPH at the Massachusetts Eye and Ear for their contributions to this article on pediatric ABI surgery.
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Disclosures/conflict of interest: The authors have nothing to disclose.