Localization and Performance of Auditory Brainstem Implants Based on MRI Measures of Paddle Placement

Objectives To develop and study a novel means of imaging auditory brainstem implant (ABI) paddle placement utilizing post-operative MRI images to determine correlation with ABI performance, and ideal paddle placement properties. Design Single centre retrospective review and image analysis. Setting Tertiary referral centre Participants Patients from 2009 to 2023 >18yo that received an ABI and had subsequent MRI imaging and auditory performance testing completed. Main Outcome Measures ABI paddle angulation and insertion depth measure, in addition to categories of auditory performance (CAP) score. Results Twenty-one patients with neurofibromatosis type 2 (NF2) that underwent ABI placement met inclusion criteria. The average insertional depth into the Foramen of Luschka was 1.0cm (Stdev 0.4), with average axial paddle angulation of 62.7o(Stdev 29.7o), average sagittal paddle angulation of 108.7o (Stdev 44.4o), and average coronal paddle angulation of -14.5o(Stdev 62.4o). Single variable linear regression showed a statistically significant negative relationship between insertion depth and CAP score (p=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. Conclusions 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.