Pediatric Auditory Brainstem Implantation: Surgical, Electrophysiologic, and Behavioral Outcomes

Abstract

Objectives: The objectives of this study were to demonstrate the safety of auditory brainstem implant (ABI) surgery and document the subsequent development of auditory and spoken language skills in children without neurofibromatosis type II (NFII).

Design: A prospective, single-subject observational study of ABI in children without NFII was undertaken at the University of North Carolina at Chapel Hill. Five children were enrolled under an investigational device exemption sponsored by the investigators. Over 3 years, patient demographics, medical/surgical findings, complications, device mapping, electrophysiologic measures, audiologic outcomes, and speech and language measures were collected.

Results: Five children without NFII have received ABIs to date without permanent medical sequelae, although 2 children required treatment after surgery for temporary complications. All children wear their device daily, and the benefits of sound awareness have developed slowly. Intra-and postoperative electrophysiologic measures augmented surgical placement and device programming. The slow development of audition skills precipitated limited changes in speech production but had little impact on growth in spoken language.

Conclusions: ABI surgery is safe in young children without NFII. Benefits from device use develop slowly and include sound awareness and the use of pattern and timing aspects of sound. These skills may augment progress in speech production but progress in language development is dependent upon visual communication. Further monitoring of this cohort is needed to better delineate the benefits of this intervention in this patient population.

Figure 1

Schematic of the Cochlear Nucleus ABI24M electrode pad. Orientation of the electrodes relative to the cochlear nucleus varies depending on right or left side placement. This illustrates the potential for other cranial nerve stimulation. Image courtesy of Cochlear Americas, ©2017.

Figure 2

Post-operative scans for each of the five pediatric ABI recipients. A) Subject 1. Post-operative CT scan was obtained showing ABI in good location on the left side and no evidence of intracranial hemorrhage B) Subject 2. Absent cochlea bilaterally. ABI paddle in expected position on left side. C) Subject 3. Cochleae appeared isolated from the internal auditory canal and thus cochlear implantation was not undertaken. ABI on right side. D) Subject 4. CI seen in cochlear on left ear, ABI placed on right side. E) Subject 5. ABI on right side, cochlear implant in left ear. Artifact from the ABI internal receiver obscures imaging.

Figure 3

Intra-operative eABRs recorded for the electrode pair of 8 and 3 in S3. Solid and dashed lines indicate replications recorded for the same stimulation condition. Black and dark grey lines indicate responses recorded using biphasic pulses with reversed polarity. Vertex positive peaks are labeled for these traces.

Figure 4

Objective and behavioral T Levels measured in four subjects. Each symbol represents results measured for one electrode. Results measured for different electrodes in the same subject are indicated using the same type of symbols. The dashed line presents result of linear regression.

Figure 5

Audiograms, active electrode configurations, ABI program parameters for 5 subjects. Subjects 4 and 5 continue to use a CI in the contralateral ear and CI responses are designated as CL. All children were programmed in a SPeak coding strategy with variable numbers of active electrodes, current levels and pulse width. Average charge per channel [nanoCoulombs (nC)] was calculated by converting clinical units used in the software using the formula (100^{(clinical level/255)}*17.5)*(pulse width/1,000).