Magnet Dislocation: An Increasing and Serious Complication Following MRI in Patients with Cochlear Implants

Abstract

Purpose: Cochlear implantation (CI) represents the gold standard in the treatment of children born deaf and postlingually deafened adults. Initial magnetic resonance imaging (MRI) was contraindicated in CI users. Meanwhile, there are specific recommendations concerning MRI compatibility depending on the type of CI system and the device manufacturer. Some CI systems are even approved for MRI with the internal magnet left in place. The aim of this study was to analyze all magnet revision surgeries in CI patients at one CI center and the relationship to MRI scans over time. Materials and Methods: Between 2000 and 2013, a total of 2027 CIs were implanted. The number of magnet dislocation (MD) surgeries and their causes was assessed retrospectively. Results: In total 12 cases of MD resulting from an MRI scan (0.59?%) were observed, accounting for 52.2?% of all magnetic revision surgeries. As per the labeling, it was considered safe to leave the internal magnet in place during MRI while following specific manufacturer recommendations: MRI intensity of 1.5 Tesla (T) and compression head bandage during examination. Conclusion: A compression head bandage in a 1.5?T MRI unit does not safely prevent MD and the related serious complications in CI recipients. We recommend a Stenvers view radiograph after MRI with the internal magnet in place for early identification of MD, at least in the case of pain during or after MRI examination. MRI in CI patients should be indicated with restraint and patients should be explicitly informed about the possible risks. Recommendations regarding MRI compatibility and the handling of CI patients issued with MRI for the most common CI systems are summarized. Key Points: ??MRI in CI patients: manufacturer recommendations must be followed. ??Magnet dislocation due to MRI is a serious complication. ??In case of suspected magnet dislocation: Use Stenvers view radiograph for diagnosis. ??Instant presentation to a CI center is mandatory for proper management of dislocation. ??Immediate CI revision surgery must be performed in the case of magnet dislocation. Citation Format: ??Hassepass F, Stabenau V, Arndt S et?al. Magnet Dislocation: An Increasing and Serious Complication Following MRI in Patients with Cochlear Implants. Fortschr R?ntgenstr 2014; 186: 680???685

Implementation of a comprehensive MR safety course for medical students

“…Alternatively, situations do occur where, despite the fact that an implant is known not to be MRI‐compatible, there are circumstances where the MRI risk is clinically acceptable. For example, many cochlear implants are fixed with ferromagnetic materials and are prone to displacement even when scanning other parts of the body with MRI . The increasing frequency of cochlear implants requires a team of physicians to evaluate the patient's risk of implant displacement (and subsequent need for surgical revision) with the medical necessity of the MRI for whatever serious, unrelated condition the patient may have.…”

“…There are additionally some devices that will malfunction once exposed to such a powerful magnetic field because the forces cause permanent and irreparable damage. Finally, there are new implants that have not been tested or labeled yet for MRI compatibility . This can pose a unique challenge requiring close collaboration between the radiology team, the ordering physician, and the physician who placed the implant.…”

“…For example, many cochlear implants are fixed with ferromagnetic materials and are prone to displacement even when scanning other parts of the body with MRI. 15 The increasing frequency of cochlear implants requires a team of physicians to evaluate the patient's risk of implant displacement (and subsequent need for surgical revision) with the medical necessity of the MRI for whatever serious, unrelated condition the patient may have. A critical decision must be made depending on the area being scanned, particulars about the implant, and the patient's likelihood to tolerate revision (meaning, how stable they are for surgery if the implant is displaced while in the MRI).…”

“…Finally, there are new implants that have not been tested or labeled yet for MRI compatibility. 15 This can pose a unique challenge requiring close collaboration between the radiology team, the ordering physician, and the physician who placed the implant. Therefore, any MRI safety module for medical students should contain a thorough description of implant safety.…”

Magnetic resonance safety

“…Even non-ferromagnetic implants can cause heating due to eddy currents that propagate in metals exposed to oscillating magnetic fields [102,103]. Especially orthopedic implants such as external fixation systems can cause heating in an MRI scanner [6,144,7,145,149,4,103,10,107] and some of the new implants or devices have not been tested or labeled for MRI compatibility [150]. It is therefore essential to establish a close collaboration between the radiology team, the ordering physician, and the physician who placed the implant [13].…”