Triphasic Pulses in Cochlear Implant Patients With Facial Nerve Stimulation

Abstract

Objective: Evaluation of triphasic pulse stimulation in comparison to the traditional biphasic pulse stimulation in cochlear implant (CI) patients with unintended facial nerve costimulation. Study Design: Retrospective case review. Setting: Cochlear Implant Center of a University Department of Otolaryngology, Head and Neck Surgery. Patients: Fifteen CI patients (MED-EL, Innsbruck, Austria) received a triphasic fitting map instead of a biphasic fitting map due to a previous diagnosis of facial nerve stimulation or stimulus induced pain during the years 2014 to 2017. Intervention(s): Application of a triphasic stimulation strategy. Main Outcome Measure(s): Reduction of facial nerve costimulation and speech understanding. Biphasic and triphasic fitting maps were compared to accurately assess the effects of the switch, and hearing tests (monosyllables and sentences in noise tests) were analyzed. Results: Triphasic pulse stimulation showed a significant reduction of unintended side effects and resulted in an observed improved quality of life in most cases. Although there was no significant change in the understanding of speech with CI in all test situations, in many cases, improvement was observed. Conclusions: Triphasic pulse stimulation had a beneficial effect for CI patients with severe, unintended costimulation and should be considered a valuable tool during CI fitting.

Investigating Facial Nerve Stimulation After Cochlear Implantation in Adult and Pediatric Recipients

“…FNS was either completely or partially eliminated during this study using various programming techniques during fitting, such as deactivating channels, changing the phase duration, changing the coding strategy, or using triphasic pulses. Previous studies have reported good results with the use of triphasic pulses instead of biphasic pulses, 2,15–17 and they proved effective in our study for reducing FNS, particularly for higher‐grade FNS. Triphasic pulses reduce the effects of FNS by distributing the charge across two negative phases of the same duration and one positive phase with a double duration time 2 .…”

“…Previous studies have reported good results with the use of triphasic pulses instead of biphasic pulses, 2,15–17 and they proved effective in our study for reducing FNS, particularly for higher‐grade FNS. Triphasic pulses reduce the effects of FNS by distributing the charge across two negative phases of the same duration and one positive phase with a double duration time 2 . However, it is important to note that deactivating channels, changing phase duration, or changing the coding strategy can reduce FNS with the consequence of a reduction in hearing abilities due to the use of a less‐than‐optimal fitting map.…”

“…The onset of FNS can be difficult to determine, because it often increases over time or develops as a result of a new fitting map. Diagnosis of FNS often relies on the CI recipients to self‐report it to the clinic 2 . This can prove difficult for pediatric CI recipients, where FNS often remains unidentified, misdiagnosed, or unreported 3 …”

“…Regardless of the cause, between 1% and 15% of CI recipients have been reported as experiencing FNS postactivation 6–12 . Higher levels have been reported in recipients with cochlear malformation, ossification, temporal bone fractures, or other etiologies, with levels as high as 75% reported in CI recipients with otosclerosis 2,7,8,11,13,14 …”

“…Several methods have been applied to reduce the effects of FNS. These include changing the mapping program, turning off the electrode contacts that are causing FNS, changing the current levels, or using triphasic pulses instead of biphasic pulses 2,15–17 . However, these strategies can sometimes result in a less than ideal fitting map for the CI recipient 12 .…”