Performance of cochlear implant recipients fitted with triphasic pulse patterns

Abstract

Purpose: To assess the effect of triphasic pulse pattern stimulation strategy on the audiological performance of cochlear implant recipients with unintended facial nerve stimulation (FNS), and to compare the audiological and speech outcomes before and after switching to triphasic stimulation. Methods: A retrospective study of patients who have changed their fitting maps from biphasic to triphasic pulse pattern stimulation because of FNS after cochlear implantation (CI). All identified patients with FNS after CI from 2017 to 2019 were included in this study. The medical records of 11 patients (16 ears) were queried for demographic and radiological data, pure tone audiometry, speech reception thresholds, speech discrimination score at 65 dB, maximum comfortable levels, thresholds, and dynamic range. Then, these parameters were compared in the two conditions, biphasic and triphasic. Results: Using triphasic pulse stimulation only or combined with switch-off of few channels, complete resolution of FNS was achieved. Triphasic pulse pattern stimulation was associated with better speech discrimination scores (75.25 ± 26.13%) compared to the biphasic pulse (58.25 ± 26.13%). This triphasic strategy also showed higher maximum comfortable levels (36.62 ± 1.63 qu) than biphasic strategy (31.58 ± 2.5 qu). Moreover, the dynamic range was wider using triphasic pulse strategy. In general, the triphasic pulse pattern resulted in successful suppression of facial nerve stimulation with suitable maximum comfortable levels and better speech discrimination. Conclusion: Triphasic pulse pattern stimulation is an appropriate tool in controlling FNS following cochlear implantation with wider dynamic range. We recommend that all patients with facial nerve stimulation after CI surgery be switched to a triphasic pulse program prior to considering further surgery.