Management of Severe Facial Nerve Cross Stimulation by Cochlear Implant Replacement to Change Pulse Shape and Grounding Configuration: A Case-series

Abstract

§Guy's and St. Thomas' NHS Foundation Trust, London; and jjOticon Medical, UK Objectives: To investigate the combined effect of changing pulse shape and grounding configuration to manage facial nerve stimulation (FNS) in cochlear implant (CI) recipients. Patients: Three adult CI recipients with severe FNS were offered a replacement implant when standard stimulation strategies and programming adjustments did not resolve symptoms. Our hypothesis was that the facial nerve was less likely to be activated when using anodic pulses with ''mixed-mode'' intra-cochlear and extra-cochlear current return. Intervention: All patients were reimplanted with an implant that uses a pseudo-monophasic anodic pulse shape, with mixed-mode grounding (stimulus mixed-mode anodic)-the Neuro Zti CI (Oticon Medical). This device also allows measurements of neural function and loudness with monopolar, symmetric biphasic pulses (stimulus MB), the clinical standard used by most CIs as a comparison. Main Outcome Measures: The combined effect of pulse shape and grounding configuration on FNS was monitored during surgery. Following CI activation, FNS symptoms and performance with the Neuro Zti implant were compared with outcomes before reimplantation. Results: FNS could only be recorded using stimulus MB for all patients. In clinical use, all patients reported reduced FNS and showed an improvement in Bamford-Kowal-Bench sentences recognition compared with immediately before reimplantation. Bamford-Kowal-Bench scores with a male speaker were lower compared with measurements taken before the onset of severe FNS for patients 1 and 2. Conclusions: In patients where CI auditory performance was severely limited by FNS, charge-balanced pseudo-monophasic stimulation mode with a mixed-mode grounding configuration limited FNS and improved loudness percept compared with standard biphasic stimulation with monopolar grounding.

The Effects of Multi-Mode Monophasic Stimulation with Capacitive Discharge on the Facial Nerve Stimulation Reduction in Young Children with Cochlear Implants: Intraoperative Recordings

“…Thus, considering only the electrodes placed inside the cochlea and, therefore, excluding the extracochlear electrodes from the analysis, the FNS was not recorded with ST2 in any of the subjects included in this study. Our results reinforce those found by Eitutis et al [ 7 ] in adults and suggest that the stimulation pattern ST2 seems to have comparable effects on FNS reduction in the first CI implantation of young children.…”

“…To the best of our knowledge, this is the first study comparing intraoperative EMG action potentials between ST1 and ST2 electrical stimulation patterns in CI children recipients and providing electrophysiological evidence of ST2 on FNS reduction in this population. Similar results were recently reported by Eitutis et al [ 7 ] in three adult patients re-implanted with the Neuro Zti device due to severe FNS. Intraoperative FNS were recorded in all the three subjects with ST1, while no FNS was observed with ST2.…”

“…Some strategies have been adopted to manage FNS symptoms, including maximum comfort levels (MCL) reduction [ 7 ], pulse wide widening [ 8 ], the use of triphasic pulses [ 9 ], electrode deactivation [ 10 ] and cochlear re-implantation [ 11 ]. However, these strategies may result in auditory performance decline [ 7 ] and does not ensure to resolve FNS [ 8 ].…”

“…Recently, the use of the multi-mode monophasic stimulation was proposed as a promising strategy to manage FNS [ 7 , 12 , 13 ]. It resolved severe FNS in some adult CI recipients, after cochlear re-implantation with the Neuro Zti device (Oticon Medical, Smørum, Denmark).…”

Current distribution of distributed all-polar cochlear implant stimulation mode measured in-situ

“…However, a rising interest using DAP that shows to minimize cases of facial nerve stimulation (FNS) still occurring in about 5.6% of the CI population [ 37 ]. For instance, two studies evaluated re-implantations of patients issuing FNS with a CI system, replaced by a Neuro Zti CI and ended with a complete resolution of the problem [ 33 , 38 ]. The main contributor for this FNS occurrence reduction is still unclear and may be related to the stimulation mode, the pulse waveform, or another parameter of the electrical stimulation.…”