Extrusion of straight cochlear implant electrodes May be diminished by proximal fixation

To determine if proximal fixation of the cochlear implant helps reduce the rate of straight electrode array extrusion/migration.

Records of 278 children implanted with a straight electrode at a tertiary pediatric hospital from 1990 to 2017 were reviewed. Demographics, operative reports, electrode type, radiological studies and audiological assessments including impedance and stimulation parameters were collected. Significant abnormalities were defined by >75% change in impedance relative to 1 month post-implant values. The main outcome is the incidence of electrode extrusion based on significant changes in impedance and comparative radiological imaging looking for electrode extrusion.

During this period, straight electrodes were chosen infrequently (298/1781 devices implanted (16.73%) in 278 children). They were used prior to the introduction of pre-curved electrodes (153/298) and subsequently for hearing preservation (33/298) and in anomalous cochleae (48/298). Most recently they were used in a comparative study of children receiving one perimodiolar and one straight array (64/298). All electrodes were proximally fixated with a suture around the incus buttress (Ned's knot). None of the 298 electrodes required repositioning. Comparative radiographs after long duration implant use were available in 72 of 298 devices (24.2%) revealing no changes in electrode position. Significant impedance changes (>75%), indicative of open circuits, were noted in 6/298 devices (2%); ≤2 electrodes at various array positions were affected in each child. In one case, repositioning of the receiver/stimulator may have damaged the electrodes as they exited the device body but no changes in electrode position were evident on the post-repositioning radiograph.

Extrusion of straight electrodes is a recognized complication of cochlear implant surgery but was not observed in our cohort with proximal electrode fixation.