Electrode Array Displacement into the Fallopian Canal in Revisions of Long-standing Cochlear Implants


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Abstract

Objective:To describe extracochlear extension of revision cochlear implant arrays into the Fallopian canal.Patients:Two adult patients with extension of revision cochlear implant arrays into the Fallopian canal.Interventions:Computed tomography (CT), selective deactivation of non-functional electrodes.Main Outcome Measures:Facial nerve function, facial nerve stimulation, cochlear implant electrode position, radiography, functional hearing.Results:Two patients presented with failure of their long-standing cochlear implants (CIs). One patient with presumed postviral hearing loss presented with declining function and increasing facial stimulation from an implant placed 30 years previous. A second with postmeningitic hearing loss presented with a draining mastoid fistula from an implant placed 7 years before. Both patients were reimplanted with minimal insertion resistance via the established electrode tract, yet demonstrated facial nerve stimulation during intraoperative telemetry and on device activation. Postoperative CTs of each patient showed exit of the electrode from the cochlea into the tympanic or labyrinthine Fallopian canal. Both patients can use their devices effectively with selective electrode deactivation.Conclusions:Our cases illustrate the potential association of long-standing electrodes with otic capsule changes, allowing extracochlear malposition of subsequent arrays. This can occur despite apparently uneventful reinsertion of a flexible array without undue force. Previously reported histopathology confirms the potential for a reactive osteitis from arrays that may contribute to this phenomenon. Intraoperative facial stimulation with neural telemetry testing can raise suspicion of a malpositioned array involving the Fallopian canal. Such cases can be effectively managed with selective deactivation of malpositioned electrode contacts.

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