Systematic Review of the Adverse Events in Patients with Cochlear Implants following MRI

Cochlear implants (CIs) are increasingly used for the treatment of sensorineural hearing loss. MRI is an essential diagnostic technique, but concerns about adverse events related to CIs have prompted device and imaging protocol innovations. The transition from axial to diametric internal magnets has significantly improved MRI safety. Despite regulatory approvals for MRI use with CIs under specified conditions, adverse events continue to be reported. In addition, many patients still have CIs with axial internal magnets.

Our goal was to summarize the types and frequencies of adverse events experienced by patients with Cis undergoing MRI and to identify factors influencing these outcomes.

A comprehensive literature search was conducted across EMBASE, MEDLINE, Ovid HealthStar, Amedsys, and gray literature up to March 16, 2024.

Fourteen observational studies (10 retrospective, 4 prospective) involving human subjects and published in English were included. Case reports, book chapters, conference abstracts, reviews, and in vitro studies were excluded.

Two independent reviewers assessed and extracted data on patient demographics, internal magnet type (axial versus diametric), MRI field strength, and adverse events. Subanalyses were performed when data permitted.

Across 814 MRIs in 668 CI ears, 167 adverse events were reported (20% prevalence). Pain was the most common (51%), followed by magnet displacement (22%) and polarity reversal (2%). No adverse events were reported in patients with diametric magnets. Events were more frequent with axial magnets and predominantly occurred with 1.5T scanners, though usage bias toward 1.5T limits comparison. Mitigating measures (eg, head wrapping, anesthesia, anxiolytics) were commonly used but were not universally effective. Pediatric populations were underrepresented and not analyzed separately.

Heterogeneity in study design, MRI protocols, reporting of adverse events, and lack of standardization in patient characteristics limit generalizability. Imaging sequence parameters and scan duration were often unspecified.

Adverse events during MRI in patients with CIs are not uncommon, particularly with axial magnets. Diametric magnets demonstrate improved safety profiles. Standardization of imaging protocols, patient preparation, and device-specific guidelines is essential to minimize risks. Future studies should document MRI parameters and patient characteristics when reporting adverse events to further assess for related or causative factors.