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.

Effects of Electrode Array Length on Frequency-Place Mismatch and Speech Perception with Cochlear Implants

“…These aspects appeared even more crucial in our study since we used much longer electrode arrays than those used in these two studies. As yet, however, it is difficult to control the insertion depth of the electrode during surgery despite the use of preoperative imaging [Viccaro et al, 2009]. Thus, another adjustment will consist in adapting the stimulation frequency map to the postoperatively assessed electrode position.…”

Acute Meningitis by Streptococcus suis

“…In our case, these values were normal, which indicates the correct insertion of the electrode and the indemnity of the cochlea. 13 We point out the importance of history taking to alert about the suspicion of the existence of this agent, mainly in meningitis and bacteraemia; because, even if it may not have any therapeutic implication, it is of great epidemiological importance due to the increase in different countries of documented cases associated to raising or manipulating porcine livestock. 14 The rarity of the meningitis caused by S. suis should not make us forget about the importance of recording the occupational hazard in the medical history.…”

“…In surgery, there are three ways of ensuring that the insertion has been correct: the first is the nonresistance to electrode insertion through cochleostomy, the second is Neural Response Imaging (NRI) and the third is radioscopy. 13 NRI is a method that allows measuring cochlear impedance and the responses of the auditive nerve through cochlear stimulation, once the electrodes have been inserted. In our case, these values were normal, which indicates the correct insertion of the electrode and the indemnity of the cochlea.…”

Necesidad de la radiología intraoperatoria para confirmar la correcta colocación del electrodo en la implantación coclear

“…Aproximadamente en 4,39% requieren revisión quirúrgica por estos motivos 6 . Sólo el control intraoperatorio radiológico puede describir exactamente la inserción correcta en la rampa timpánica, por lo tanto, es imprescindible la realización de una radiológica intraoperatoria para confirmar la perfecta colocación intracoclear del electrodo, o en su defecto, poder proceder a su recolocación en el mismo acto quirúrgico 7,8 situación de este caso clínico. Independientemente del sistema de imagen intraoperatorio utilizado 9 , la radiografía intraoperatoria del implante coclear, asequible para la mayoría de los hospitales, es una herramienta fundamental y obligada, ya que permite al cirujano no sólo evaluar la posición, sino también la integridad del electrodo, y permitir la intervención inmediata, cuando ésta sea necesaria la sustitución o recolocación del mismo.…”