(877) Relationship between electrode-modiolus distance and MAPping patterns on perimodiolar cochlear implant arrays

Introduction: Current clinical recommendations for programming a slim perimodiolar electrode entail using a “population mean” algorithm for threshold (T) and comfort (C) level setting (MAPping). Our institution identified a series of patient programs that exhibit patterns that may differ from the suggested population mean. These patients have a “checkmark” pattern in stimulation levels: average T levels at the apical electrodes, lower T levels at mid-apical electrodes (electrodes 15-17), and rising thereafter through the basal end of the array. The objective of this study was to determine whether electrode–modiolus distance (EMD) on postoperative CT correlates with “checkmark” patterns observed at our institution.

Methods: 25 post-operative temporal bone CT scans in patients implanted with slim perimodiolar arrays and their associated MAP’s were analyzed . Using CT-based measures, EMD was measured across intracochlear electrode contacts and correlated with electrical T levels extracted at the one-month post-implantation programming visit. T levels were also categorized by the presence of “checkmark” pattern observed in perimodiolar arrays. Secondary analyses evaluated whether associations vary by electrode position along the array and if T levels varied between pattern groups.

Results: Variations in EMD are associated with the observed checkmark T level patterns, supporting electrode position as a structural correlate of T and C level findings.

Conclusions: CT-derived EMD may provide an imaging biomarker of perimodiolar positioning and help explain variability in T levels during follow-up. Correlating T and C levels to EMD may inform surgical techniques in cochlear implantation to optimize electrode position and programming parameters.