Spread of excitation measurements for the detection of electrode array foldovers: a prospective study comparing 3-dimensional rotational x-ray and intraoperative spread of excitation measurements

The optimal positioning of electrode arrays in the cochlea is extremely important. Our standard approach is to use a 3-dimensional rotational x-ray for the intraoperative determination of the position of the electrode array. We wanted to see if spread of excitation (SOE) is useful for determining the electrode array position within the cochlea. Prospective blind study design. Tertiary University Referral Center (Cochlear Implantation Center Amsterdam-Academic Medical Center, University of Amsterdam). Seventy-two implanted ears with a Cochlear Freedom device. After cochlear implantation, we compared the 3-dimensional rotational x-ray imaging and SOE measurements. The investigators were blinded for the intraoperative surgeon findings and also for the imaging findings. Electrode array foldovers within the cochlea and the reliability of the SOE measurements. We placed implants in 72 ears in this study, and all procedures seemed to be surgically uneventful. To our surprise, we discovered 4 electrode foldovers in this group. Of the 4 foldovers, 3 were corrected intraoperatively. We found that intraoperative imaging and/or electrophysiologic measurements such as the SOE provide very useful information regarding electrode position within the cochlea. Spread of excitation is effective in detecting electrode array foldovers if the audiologist is experienced. Some software modifications are suggested.