Faculty Bibliography

OBJECTIVES/UNASSIGNED:To better understand the implications of tumor size on auditory brainstem implant (ABI) categories of auditory performance (CAP) score to facilitate more precise patient counselling. DESIGN/UNASSIGNED:Single-center retrospective chart review. SETTING/UNASSIGNED:Tertiary referral center. PARTICIPANTS/UNASSIGNED:Patients > 18 years old with neurofibromatosis type 2 who underwent ABI placement between the years 2009 and 2023 were included. Patients with prior surgical resection were excluded to reduce the potential of previous cochlear nucleus trauma confounding results. MAIN OUTCOME MEASURES/UNASSIGNED:Ipsilateral tumor volume was measured from the preoperative MRI, and the primary endpoint was the 1-year CAP score. RESULTS/UNASSIGNED: = 0.010). CONCLUSION/UNASSIGNED:Increased tumor size has a negative correlation with ultimate ABI performance. There were patients in this study with larger tumor sizes who still benefited from ABI placement. While larger tumor size should not be a contraindication for ABI placement, understanding the role tumor size can have on performance variation can serve to improve tumor management strategies and preoperative counselling.

OBJECTIVES/UNASSIGNED:To develop and study a novel means of imaging auditory brainstem implant (ABI) paddle placement utilizing postoperative MRI images to determine correlation between ABI performance and ideal paddle placement properties. DESIGN/UNASSIGNED:Single-center retrospective review and image analysis. SETTING/UNASSIGNED:Tertiary referral center. PARTICIPANTS/UNASSIGNED:Patients >18 years old who received an ABI from 2009 to 2023 and had subsequent MRI and auditory performance testing completed. MAIN OUTCOME MEASURES/UNASSIGNED:ABI paddle angulation and insertion depth measure, in addition to categories of auditory performance (CAP) score. RESULTS/UNASSIGNED: = 0.049) once patients with large tumor burden were excluded. Insertion depth and axial angulation showed a negative correlation, in which higher insertion depth was associated with a decrease in axial angulation value, although not statistically significant. CONCLUSION/UNASSIGNED:We present a novel means of measuring ABI paddle placement utilizing MRI to improve the objectivity of paddle placements assessments. Multicenter collaboration to increase the number of patients studied with this new measurement scheme will be required before stronger measurement associations can be determined.

OBJECTIVE:We sought to apply a previously developed transimpedance (TIM) heatmap pattern classification scheme in patients with no known risk factors for cochlear anomalies, in addition to patients implanted in the revision setting, to better understand the incidence of pattern variants, and potential clinical implications. STUDY DESIGN/METHODS:Single-center retrospective review. SETTING/METHODS:Tertiary referral centre. PATIENTS/METHODS:Patients older than 6 months of age who underwent cochlear implantation between June 2020 and June 2024 with normal gross cochlear anatomy and no concern for fibrosis that had intraoperative TIM testing completed. Patients undergoing revision implantation were also included as a separate cohort. INTERVENTION/METHODS:None. MAIN OUTCOME MEASURES/METHODS:The number of patients with normal and variant TIM patterns was evaluated for each cohort. TIM patterns were subsequently compared with the electrode position found on intraoperative x-ray. RESULTS:There were 321 ears that underwent implantation and subsequent intraoperative TIM assessment meeting inclusion criteria. Of these, 310 (96.6%) were in the primary surgery setting, and 11 (3.4%) were in the revision surgical setting. In the primary surgical setting, 86.4% (n=268) of the implants demonstrated a normal TIM heatmap. Compared with the primary surgical setting, where only 45.5% (n=5) of revision surgery TIM heatmaps were interpreted as normal. One patient in the revision setting had a newly identified "double X" pattern corresponding to a normal electrode position on x-ray. CONCLUSIONS:There is a decreased incidence of previously developed TIM heatmap pattern variants in CI recipients with normal gross cochlear anatomy.

Cochlear implants are neuroprosthetic devices that restore hearing and speech comprehension to profoundly deaf humans, and represent an exemplar application of biomedical engineering and research to clinical conditions. However, the utility of these devices in many subjects is limited, largely due to lack of information about how neural circuits respond to implant stimulation. Recently we showed that deafened rats can use cochlear implants to recognize sounds, and that this training refined the responses of single neurons in the primary auditory cortex. Here we asked how local populations of cortical neurons represent acute implant stimuli, using electrode arrays we developed for cortical surface recordings for micro-electrocorticography (μECoG), a form of intracranial electroencephalography (iEEG). We found that there was a limited tonotopic organization across recording sites, relative to a clearer tonotopic spatial representation in normal-hearing rats. Single-trial iEEG responses to acoustic inputs were more reliable than responses to cochlear implant stimulation, although stimulus identity could be successfully decoded in both cases. However, the spatio-temporal response profiles to acoustic vs cochlear implant stimulation were substantially different. Decoders trained on acoustic responses showed essentially zero information transfer when tested on electrical stimulation responses in the same animals after deafening and cochlear implant stimulation. Thus while acute cochlear implant stimulation might activate the auditory cortex in a cochleotopic manner, the dynamics of network activity are quite distinct, suggesting that pitch percepts from acoustic and electrical stimulation are fundamentally different.

Developed by the Center for Robust Speech Systems at the University of Texas at Dallas, in collaboration with New York University and the University of Wisconsin-Madison, CCi-MOBILE addresses a critical challenge in optimizing cochlear implant (CI) fitting and enhancing sound coding strategies. Existing clinical CI processors and research tools often lack either the necessary computational power and flexibility or the portability required for real-world testing. CCi-MOBILE bridges this gap by enabling the implementation and evaluation of diverse real-time sound coding algorithms in both laboratory and real-world settings, including those requiring synchronized bilateral stimulation. Building upon previous publications, this paper provides new detailed discussion on parameter setting for stimulus generation with CCi-MOBILE and serves as a comprehensive resource for scientists and engineers developing novel real-time sound coding and signal processing strategies with this platform. As part of an ongoing development effort, future generations of CCi-MOBILE may offer additional functionalities beyond those described here.

OBJECTIVES/OBJECTIVE:To provide a level-adjusted correction to the current standard relating anatomical cochlear place to characteristic frequency (CF) in humans, and to re-evaluate anatomical frequency mismatch in cochlear implant (CI recipients considering this correction. It is proposed that a level-adjusted place-frequency function may represent a more relevant tonotopic benchmark for CIs in comparison to the current standard. DESIGN/METHODS:The present analytical study compiled data from 15 previous animal studies that reported isointensity responses from cochlear structures at different stimulation levels. Extracted outcome measures were CFs and centroid-based best frequencies at 70 dB SPL input from 47 specimens spanning a broad range of cochlear locations. A simple relationship was used to transform these measures to human estimates of characteristic and best frequencies, and nonlinear regression was applied to these estimates to determine how the standard human place-frequency function should be adjusted to reflect best frequency rather than CF. The proposed level-adjusted correction was then compared with average place-frequency positions of commonly used CI devices when programmed with clinical settings. RESULTS:The present study showed that the best frequency at 70 dB SPL (BF70) tends to shift away from CF. The amount of shift was statistically significant (signed-rank test z = 5.143, p < 0.001), but the amount and direction of shift depended on cochlear location. At cochlear locations up to 600° from the base, BF70 shifted downward in frequency relative to CF by about 4 semitones on average. Beyond 600° from the base, BF70 shifted upward in frequency relative to CF by about 6 semitones on average. In terms of spread (90% prediction interval), the amount of shift between CF and BF70 varied from relatively no shift to nearly an octave of shift. With the new level-adjusted place-frequency function, the amount of anatomical frequency mismatch for devices programmed with standard-of-care settings is less extreme than originally thought and may be nonexistent for all but the most apical electrodes. CONCLUSIONS:The present study validates the current standard for relating cochlear place to CF, and introduces a level-adjusted correction for how best frequency shifts away from CF at moderately loud stimulation levels. This correction may represent a more relevant tonotopic reference for CIs. To the extent that it does, its implementation may potentially enhance perceptual accommodation and speech understanding in CI users, thereby improving CI outcomes and contributing to advancements in the programming and clinical management of CIs.

OBJECTIVES/UNASSIGNED:This study aims to synthesize current knowledge and outcomes related to pediatric auditory brainstem implantation (ABI) in children with severe inner ear malformations (IEMs). It highlights the clinical management practices, challenges, and potential future directions for consensus development in this field. METHODS/UNASSIGNED:A systematic review of findings presented at the Third International Pediatric ABI Symposium organized by the Hacettepe Cochlear Implant team between 3 and 5 September 2020 was conducted, incorporating data from 41 departments across 19 countries. Relevant clinical outcomes, imaging techniques, surgical approaches, and rehabilitation strategies were analyzed to identify key trends and variability in practices. RESULTS/UNASSIGNED:The review indicates that children receiving ABIs exhibit diverse auditory outcomes influenced by individual anatomical variations and developmental factors. Early implantation, particularly before the age of three, positively correlates with better auditory and language development. Multicenter experiences underscore the necessity of tailored decision-making, which considers both surgical candidacy and comprehensive rehabilitation resources. DISCUSSION:/UNASSIGNED:The variability in outcomes emphasizes the need for improved consensus and guidelines regarding eligibility, surgical techniques, and multidisciplinary rehabilitation approaches. Notable complications and the necessity for thorough imaging assessments were also identified as critical components affecting clinical decisions. CONCLUSION/UNASSIGNED:A formal consensus statement is warranted to standardize best practices in ABI management. This will not only enhance patient outcomes but also guide future research efforts to address the remaining challenges in the treatment of children with severe IEMs. Enhanced collaboration among team members will be pivotal in achieving these objectives.

Although cochlear implants (CI) successfully replace the sense of hearing, they do not restore natural hearing. Still, CI users adapt to this novel signal, reaching meaningful levels of speech recognition in clinical tests that focus on repetition of words and short sentences. However, many patients who score above average in clinical speech perception tests complain that everyday speech interactions are both difficult and cognitively draining. In part this difficulty may be due to the naturally rapid pace of everyday discourse. We report a study in which 12 CI users aged 23 to 77, recalled multi-sentence discourse presented without interruption, or in the condition of interest, when passages were paused at major linguistic boundaries, with participants given control of when to initiate the next segment. Comprehension of the discourse structure was based on a formalized representational system that organizes discourse elements hierarchically to index the relative importance of different elements to the overall understanding of the discourse. Results showed (a) better recall when CI users were allowed to control the discourse pace, (b) an overall effect of aging, with older CI users recalling discourse less accurately, (c) better recall for passages with higher average inter-word predictability, (d) a "semantic hierarchy effect" reflected by better recall of main ideas versus minor details, (e) an attenuation of the semantic hierarchy effect for low predictability passages. Results underscore the benefits of extra processing time in addressing CI listening challenges and highlight the limited ecological validity of single-word or single-sentence speech recognition tests.