The importance of intra-operative imaging during cochlear implant surgery

Abstract

Two unusual cases of cochlear implant (CI) surgery complication are reported: introduction of the electrode array into the superior semicircular canal with normal morphology and a growing amplitude of neural potential (neural response imaging, NRI) during intra‐operative monitoring control. In the first case, a two‐year‐old patient affected by congenital sensorineural profound deafness was bilaterally implanted with two Clarion 90 k devices and intra‐operative electrophysiological and radiological controls were performed. After introduction of the array in the right side NRI was performed and a neural potential was found only on two apical electrodes. Radiological intra‐operative control with antero‐posterior trans‐orbital plain films was performed to assess the position of the electrodes inside the cochlea. Radiography showed the electrode array in the superior semicircular canal in the right ear. The electrode array was removed and reinserted correctly. In the second case, a 72‐year‐old man underwent left cochlear implantation for sensorineural profound deafness of unknown origin. Intra‐operative electrophysiological testing (NRI) showed the presence of neural potential on three tested channels. In this case, as routinely employed since 2006, an intra‐operative static fluoroscopy control was performed, this showed the electrode array in the superior semicircular canal. The electrode array was removed and reinserted correctly. In conclusion, intra‐operative monitoring tests during CI surgery play different roles: measurement of impedances and NRI can evaluate the integrity of implant electrodes and the status of the electrode cochlea interface, but they cannot be the only way to confirm correct positioning of the array. In our opinion the intra‐operative radiological check is helpful during CI surgery, especially when there is any doubt about correct electrode insertion. Copyright © 2009 John Wiley & Sons, Ltd.

Value of Routine Plain X-Ray Position Checks after Cochlear Implantation

“…The findings of our study argue for routine radiographic position checks because intraoperative findings only have a limited predictive value. This conclusion is in accordance to surgeons who rank radiographic position checks as so important that they perform intraoperative position checks, for example, (9,10), which have the added advantage that instant corrections of electrode position can be performed.…”

Cochlear implant electrode misplacement: Incidence, evaluation, and management

“…In another two cases presented by Viccaro et al,17 where the electrode array was misplaced into the superior semicircular canal, stimulated channels gave a response with normal morphology and a growing amplitude at increasing stimulation intensity. It was hypothesized that the near‐normal neural responses obtained were probably due to a spread of the current secondary to the high stimulation intensity, similar to the response observed when the electrode array is placed in the cochlea.…”

“…In all cases there was either absent or abnormal intraoperative neural response telemetry that lead to intraoperative imaging. In all revision cases, the cochleostomy was widened antero‐inferiorly to allow correct insertion of the electrode array 13, 17, 18…”

Utility of intraoperative imaging in cochlear implantation: A systematic review

“…Both studies cited the risk of cataracts due to radiation exposure and discussed the potential for the preoperative CT scan and possible multiple intraoperative radiographs culminating in a harmful amount of radiation, especially in the pediatric population. However, the other five studies examining intraoperative X‐ray in this systematic review concluded that intraoperative X‐ray was useful . The rate of electrode misplacement across these studies, 2.2%, is low but not negligible, which is considered to be a major complication because accurate placement is critical for successful auditory rehabilitation .…”

“…However, the other five studies examining intraoperative X-ray in this systematic review concluded that intraoperative X-ray was useful. 9,12,[22][23][24] The rate of electrode misplacement across these studies, 2.2%, is low but not negligible, which is considered to be a major complication because accurate placement is critical for successful auditory rehabilitation. 19 Revision surgery in these patients incurs additional cost and may cause increased morbidity.…”