Abstract
Cochlear implants (CI) have now become a standard method of treating severe to profound hearing loss. Recently, the number of patients with CI has been rapidly increasing as the big benefits of CI become more widely known. Magnetic resonance imaging (MRI) has also become a routine diagnostic imaging modality, used in the diagnosis of common conditions, including stroke, back pain, and headache. We report our recent experience with a case in which internal magnet of the cochlear implant was reversed after 1.5-T lumbar spine MRI. This complication is managed successfully by reversing the orientation of the external magnet in the head coil.
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Introduction
Cochlear implants (CI) have now become a standard method of treating severe to profound hearing loss. Recently, the number of patients with CI has been rapidly increasing as the big benefits of CI become more widely known. Magnetic resonance imaging (MRI) has also become a routine diagnostic imaging modality, used in the diagnosis of common conditions affecting large segments of the population, including stroke, back pain, and headache. MRI uses pulses of radio waves within magnetic fields to generate images. Currently, MR instruments operating at 1.5-T field strength are common .
CI manufacturers developed several strategies to increase the compatibility and safety of MRI scanning in CI users . Current US Food and Drug Administration guidelines allow limited use of MRI in CI recipients. The Pulsar, Sonata, and Concerto devices (Med-El Corporation, Innsbruck, Austria) are approved for 0.2-T MRI scanning with magnet in place. The Hi-Res 90K implant (Advanced Bionics Corporation, Sylmar, CA) is approved for up to 1.5-T MRI after surgical removal of the magnet. Nucleus devices (Cochlear Americas, Englewood, CO) are approved for up to 3-T MRI without magnet (CI24 series, CI422 and CI500) and for up to 1.5-T MRI with magnet in place .
We report our recent experience with a case in which internal magnet of the cochlear implant was reversed after 1.5-T lumbar spine MRI, along with a literature review. This study was approved by the institutional review board of our hospital.
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Case reports
A 73-year-old woman with bilateral severe hearing loss underwent left Nucleus 24R Contour Advance (Cochlear Corporation, Sydney, Australia) in our hospital 7 years ago. Her auditory performance was excellent with categories of auditory performance (CAP) of 7. She had recently complained of back pain and underwent a 1.5-T lumbar spine MRI without a head compression bandage and consulting ENT specialist at another hospital. While undergoing MRI, she suddenly complained of pain and discomfort in the left temporal area. MRI scan was stopped immediately. She felt a button-like material vertically against her skull and pressed it herself. After then, the external device pushed out to the inner device. She visited our hospital promptly; we could not find any displacement of the inner device and magnet in skull lateral view ( Fig. 1 ). When we reversed the external device, it could pull the inner device ( Fig. 2 ). However, when the external device was reversed, sound perception was somewhat decreased. We decided reversing the orientation of the magnet of the external device because she did not want to undergo operation for reversing the magnet of the inner device. After reversing the polarity of the external device magnet, her auditory performance completely recovered. On follow-up, she is without any problem over 2 years.
