-to-modiolus distance is correlated with clinically programmed stimulation levels.
Conventional wisdom has long supposed a significant relationship between cochlear implant
(CI) stimulation levels and electrode
-to-modiolus distance; however, to date, no such formal investigation has been completed. Thus, the purpose of this project was to investigate the relationship between stimulation levels and electrode
-to-modiolus distance. A strong correlation between the two would suggest that stimulation levels might be used to estimate electrode
-to-modiolus distance was determined via CT imaging using validated CI position analysis software in 137 implanted ears from the three manufacturers holding FDA approval in the United States. Analysis included 2,365 total electrodes, with 1,472 from precurved arrays. Distances were compared to clinically programmed C/M levels that were converted to charge units.
Mean modiolar distance
with perimodiolar and lateral wall electrodes was 0.47 and 1.15 mm, respectively. Mean suprathreshold charge values were significantly different between each manufacturer. When combining all data, we found a moderate positive correlation (r
< 0.01) that was driven both by the different charge values across companies, and that the company with the highest mean charge values only offers straight electrode
arrays. When grouped by electrode
type, however, we found a weak correlation (r
< 0.01) for perimodiolar array electrodes only. When considering a single array type from any one manufacturer, only one was observed where distance mildly predicted charge.
Our results suggest that electrode
distance minimally contributes to the current level required for suprathreshold stimulation.