Multi-mode grounding stimulation with anodic monophasic pulses to treat/prevent anomalous facial nerve stimulation in cochlear implant: case report

Background: Cochlear implants (CIs) are a well-established treatment for individuals with severe-to-profound sensorineural hearing loss, benefiting both children and adults. However, a subset of CI users may experience unintended stimulation of non-cochlear nerves, particularly the facial nerve, resulting in involuntary facial movements triggered by sound. This phenomenon, termed anomalous facial nerve stimulation (AFNS), has a reported incidence of 5.6% (range: 0.68–43%) according to a systematic review. Risk factors for AFNS include otosclerosis, cochlear or inner ear malformations, facial nerve dehiscence, and cochlear ossification or obliteration. Device-related contributors such as lateral wall electrodes and high stimulation levels also play a role. Management typically begins with conservative programming adjustments to minimize current levels and off-cochlea dispersion. If these measures fail, deactivating specific electrodes responsible for AFNS is considered. While such interventions often preserve auditory function, performance may decline in certain cases, leading some individuals to discontinue CI use. In severe scenarios, explantation, with or without reimplantation, has been documented. Case presentation: Two clinical cases of CI users with severe-to-profound sensorineural hearing loss are described. The first case, a 57-year-old woman suffering chronic otitis media since childhood, required explantation because of severe AFNS and reimplantation with a device delivering using multi-mode grounding (MMG) stimulation with anodic monophasic pulses (AMP). The AFNS was controlled and she return to use CI with acceptable functional gain. The second case, a 27-year-old woman with bilateral otospongiosis, exhibited intraoperative facial nerve stimulation during bipolar monophasic testing, but this was prevented postoperatively using MMG + AMP. Conclusions: For CI users at risk of facial nerve stimulation (e.g., otosclerosis, cochlear malformations, facial nerve canal dehiscence, or cochlear ossification), careful device selection and programming strategies are essential to minimize current spread. CI systems with MMG and AMP can effectively manage FNS when conservative methods fail. In severe cases, explantation and reimplantation using this technology may be the better therapeutic approach.