Fifteen Years of Pediatric Auditory Brainstem Implantation

Objective: Children with cochlear nerve deficiency (CND) generally perform more poorly than average pediatric cochlear implant (CI) recipients, but exceptions exist. This raises the dilemma of selecting the procedure that might prove most beneficial. At present, CIs and not auditory brainstem implants (ABIs) are the first-line treatment for these children, even in the absence of any scientific evidence that CIs outperform ABIs and CIs. We experienced that children with CND show minimal hearing benefit from CI and most children do not show perceptual progress even with intensive rehabilitation sessions. For children with severe cochlear or cochlear nerve malformations ABIs were not considered a viable option and were left to their destiny without any hope of hearing.

In 2000 after experiencing excellent speech recognition in some non-neurofibromatosis type 2 (NF2) adults we decided to fit children with CND with ABIs. This was controversial and many otologists declared unethical to incur the risks of ABI surgery for a limited outcome, especially in children. Supported by our outcomes showing better outcomes in children with CND fitted with ABIs compared with CIs, we shifted to ABI as the first-line treatment. The acknowledgment that ABIs may provide auditory and cognitive development in children with CND induced a rapid expansion PediABI programs all over the world.

Methods: From 2000 to 2015, 103 children, ranging in age 8 months to 16 years, were implanted with ABIs, either Cochlear or Med-El, at our or outside Institution. Among these children 31 had previously been fitted elsewhere with a CI, 4 had bilateral sequential and 2 simultaneous ABIs. Etiologies included 79 cochlear nerve aplasia, 1 auditory neuropathy, 15 cochlear malformations, 3 bilateral cochlear post-meningitic ossification, 4 NF 2 and 1 bilateral cochlear fractures due to a head injury. The follow-up period ranged from 6 months to 12 years. Our protocol includes under general anesthesia, a single recording session with impedance audiometry, ABRs, RW EcoG with acoustic and electrical stimulation and if candidates for an ABI are submitted to CT and MRI studies to identify cochlear or cochlear nerves abnormalities and to neuropediatric and neuropsychological evaluation to define associate disabilities.

Parents are fully informed of the inherent risks involved, the potential perceptual and cognitive benefits of ABI surgery and of the wide range of possible outcomes. The retrosigmoid surgical approach was used in all children. The identification, correct positioning of the electrodes on the cochlear nuclei and monitoring of cranial nerves VII, IX, X, and XI are obtained with neurophysiologic intraoperative monitoring (NIM). Typical electric auditory brainstem response evoked from the implant (EABR) with 1, 2, or 3 positive peaks with latencies ranging from 0.6 to 1.6, 1.1 to 2, and 2.5 to 3.8 milliseconds are obtained from 30 to 80% of electrodes are observed. Six hours after surgery the child undergoes high-resolution CT to detect any surgical complications and remains in intensive care unit for 12 hours.

Before activation, performed 30 to 45 days after implantation, EABR under general anesthesia allows the selections of electrodes with auditory and no a myogenic activity. Gradually, over the first 3 to 6 months, the stimulation levels are increased allowing the child to gain experience with the auditory sensations and provide initial feedback. The number of electrodes observed at activation may increase at successive follow-up visits, and may be included in the maps. The main non-auditory side effects reported by the older children at ABI activation were ipsilateral body tingle in 2 (6.9%) children, facial nerve stimulation in 2 (6.9%), dizziness in 1 (3.4%), headache in 1 (3.4%), and throat tingle/tickle in 1 (3.4%) child

Results: We observed a wide range of performances across etiologies with the ABIs: (a) children who lost had hearing from cochlear fractures or ossification showed dramatic improvements, (b) children with severe genetic malformations or auditory neuropathy often with multiple handicaps obtained limited auditory benefit even after years of experience, (c) most children receiving limited auditory benefit with the ABI demonstrated significant improvements on tests of cognitive development, (d) children with cochlear nerve aplasia with no associated disabilities also showed high levels of auditory development with performances and rates of improvement similar to those observed with CIs, some with the ability to use telephone with family members over 2 years.

Conclusion: The interest on PediABI programs have rapidly spread all over the world with evidence from different institutions that PediABIs may provide auditory and cognitive development in deaf children not suitable for cochlear implants. In experienced Institutions the complications observed children fitted with ABIs are minimal and are comparable with those observed in CIs. It is now clear that the PediABI surgery risk/benefit ratio is in favor of the ABI with children.