Systematic Review of the Impact of Magnetic Resonance Imaging on Diametric Magnet Cochlear Implants

Objective Review the properties, safety, and artifacts of current cochlear implants (CI) with freely rotatable magnets during MRI scans. Databases Reviewed PubMed, Cochrane, and Web of Science; last accessed September 2023. Methods The study was BSMH IRB exempted. MESH term “magnetic resonance imaging” and phrases of “Med-el Synchrony,” “Cochlear Nucleus Profile Plus,” “Advanced Bionics HiRes Ultra 3D,” “rotatable magnet cochlear,” “rotatable magnet,” “diametric magnet,” “diametric magnet cochlear implant,” and “MRI-safe cochlear implant” using “AND” function. Non-English, non-human, non-implanted CI, and cadaveric studies were excluded. Methodological quality was assessed using the Mixed Methods Appraisal Tool, and quality of the evidence was evaluated using the GRADE criteria. Results The review included 18 studies. Fifteen assessed pain as a complication, with two reporting its occurrence: two cases for Synchrony and one for Ultra 3D. Demagnetization did not occur in the 12 studies that reported on it. One magnet displacement was noted with the Ultra 3D implant out of the 16 reporting studies. Artifacts were reported by 11 studies, with most scans retaining most to limited diagnostic usability. One Synchrony device required explantation due to artifact, and one was explanted before MRI. Conclusion Of the CI models reviewed with diametric magnets, Med-El Synchrony may enable MRI usage with fewer safety concerns when following the manufacturer's recommendations. However, clinical reports of freely rotatable CI safety during MRI scans are sparse and contain incomplete data. MRI artifacts from CI still pose concerns for image quality but can be minimized with appropriate implant location and scanning protocols.