FACIAL-NERVE STIMULATION BY A COCHLEAR IMPLANT IN A HEMODIALYSIS PATIENT WITH BONE OF LOW MINERAL DENSITY

Facial nerve stimulation by an activated cochlear implant was noted in a 56-year-old patient who had undergone cochlear implant with a Nucle us 22 implant 2 years previously as treatment for total sensorineural hearing loss following meningitis at age 54. Past history was complica ted by total renal failure for which hemodialysis had been required du ring the past 13 years. Facial spasm occurred 5 months postoperatively with activation of the basal electrodes (channels 13 and 15 of the im plant). The facial stimulation was eliminated by deprogramming these e lectrodes. High-resolusion computed tomography (CT) scanning was unabl e to demonstrate lucency of the otic capsule and cochlear ossification , but basal electrodes of the implant could be identified near the lab yrinthine segment of the facial nerve. To further evaluate bone change s in the patient, the total and regional bone mineral density (BMD) of the head and radius was measured by dual energy X-ray absorptiometry. All BMD values of the patient were markedly low when compared to thos e of 62 other hemodialysis patient. These findings demonstrate that fa cial nerve stimulation can occur in the presence of low impedance due to cortical bone changes induced by long-term hemodialysis.