The reversed internal magnet of cochlear implant after magnetic resonance imaging

Prospective study on magnetic resonance imaging in cochlear implant patients

PURPOSE

Monocentric, prospective study to investigate whether concomitant support of cochlear implant (CI) patients by CI-trained otolaryngologists and application of a standardized head bandage can minimize potential complications during magnetic resonance imaging (MRI).

METHODS

Thirty-seven patients with 46 CIs underwent MRI with a prophylactic head bandage. All participants and the otolaryngologist at the CI center completed pre- and post-MRI questionnaires documenting body region scanned, duration of MRI and bandage wear, field strength during the scan, and any complications. If pain was experienced, it was assessed using a visual analog scale (1-10).

RESULTS

MRI was performed without adverse events in 37.8% of cases. Magnet dislocation requiring surgical revision occurred in 2% of cases. Pain was reported in 86% of cases, often due to the tightness of the dressing. Patients with rotating, MRI-compatible magnets reported significantly less pain than participants with older-generation implants. In 11% of cases, the MRI was discontinued.

CONCLUSION

Serious complications during MRI in cochlear implant patients are rare. Pain is the most common adverse event, probably mainly due to the tight bandage required by most implant types. With newer generations of magnets, these patients experience less pain, no dislocation of the magnets, and no need for bandaging. Although magnet dislocation cannot be completely prevented in older generations of implants, it appears to be reduced by good patient management, which recommends examination under the guidance of physicians trained in the use of hearing implants.

Magnetic Resonancy Imaging Safety in Active Osseointegrated (Osia®) and Cochlear Implants: New Technology Creating Confusion

OBJECTIVE

There is increased confusion regarding MRI-compatible CIs and BAHAs. This report describes two cases when patients underwent MRIs with non-MRI compatible devices.

RESULTS

One patient with bilateral Cochlear Osias experienced dislocation of both internal magnets after 1.5 Tesla MRI. Both magnets were outside the silastic sheath, with the left magnet flipped. A second patient with a legacy CI experienced similar internal magnet dislocation and inversion after 3 Tesla MRI.

CONCLUSIONS

This study describes internal magnet dislocation/inversion with the Cochlear Osia and a legacy CI after MRI. Our findings suggest the need for improved patient education and simplified radiology guidelines. Laryngoscope, 134:393-396, 2024.

Impact of Cochlear Implant With Diametric Magnet on Imaging Access, Safety, and Clinical Care

Objectives/Hypothesis

Review safety and effectiveness of magnetic resonance imaging (MRI) of patients implanted with a cochlear implant (CI) containing a diametric magnet housed within the undersurface of the device.

Study Design

Retrospective chart review with additional review of MRI at a tertiary‐care children's hospital.

Methods

Seven patients with mean age of 8.4 years (range = 1.3–19 years) with a diametric magnet in situ during MRI. The intervention comprised one or more sessions of 1.5 T or 3.0 T MRI without a head wrap. The main outcome measures were the occurrence of magnet‐related complications including discomfort and magnet displacement, use of anesthesia or sedation, and clinical usefulness of MRI studies.

Results

Seven CI recipients underwent 17 episodes of 1.5 or 3.0 T MRI with an in situ diametric magnet. Thirteen of 17 (76%) MRI sessions were completed in awake patients. No patients had device‐related discomfort. No magnet‐related complications occurred. Thirteen of 14 (93%) brain studies were clinically useful despite artifacts.

Conclusions

The diametric magnet enabled MRI with magnet in situ without the discomfort or magnet displacement associated with removable axial magnets. The reduction in MRI magnet‐related complications occurred because torque is not directed perpendicular and outward from the plane of the magnet, and the magnet is securely contained within its housing. The design of this device increased access and reduced the need for sedation or anesthesia.

Level of Evidence

4 Laryngoscope, 131:E952–E956, 2021

First MRI With New Cochlear Implant With Rotatable Internal Magnet System and Proposal for Standardization of Reporting Magnet-Related Artifact Size

OBJECTIVE

To report on the first known magnetic resonance imaging (MRI) with a new cochlear implant (CI) with rotatable internal magnet system, to review the literature on MRI in cochlear implantees, and to advocate for standardization of reporting magnet-related artifact size.

STUDY DESIGN

Case report and review of literature.

SETTING

Tertiary care hospital.

RESULTS

A patient with congenital rubella and bilateral profound hearing loss was incidentally found to have a petroclival meningioma. After resection and radiosurgery, she underwent cochlear implantation with the Advanced Bionics HiRes Ultra 3D device (Advanced Bionics LLC, Valencia, CA) with rotatable internal magnet system, due to need for imaging surveillance of residual meningioma. During 1.5 T MRI brain scan without a head wrap, she experienced no adverse events. The images obtained were adequate for visualization of residual tumor. Implant recipients with non-rotatable magnets who undergo MRI, with or without recommended head wrap, may suffer various complications. All images in patients with retained internal magnets are subject to magnet-related artifact, but reports regarding its size are variable and lack detail on how measurements are made.

CONCLUSIONS

MRI in patients with a new CI device with rotatable magnet system may be performed without discomfort or device dislodgement at 1.5 T, even without a head wrap, though external magnet replacement may require multiple attempts due to internal magnet realignment. Despite significant artifact, the structure of interest may still be visualized for accurate diagnosis. Measuring magnet-related artifact size should be standardized by reporting artifact in radii at the image level of maximal signal loss.

Magnetic resonance imaging with cochlear implants and auditory brainstem implants: Are we truly practicing MRI safety?

OBJECTIVE

Our objective is to evaluate the safety in patients with cochlear implants (CIs) and auditory brainstem implants (ABI) undergoing 1.5 Tesla (T) magnetic resonance imaging (MRI). Secondly, we want to raise awareness on CI and MRI safety, and advocate for continued improvement and advancement to minimize morbidity for our CI patients.

METHODS

Retrospective case series from 2006 to 2018 at a single tertiary academic center. Data was collected on patients with CI or auditory brainstem implants undergoing MRI. Outcomes collected include demographic data, age at time of MRI, MRI characteristics, complications, CI manufacturer, and image quality.

RESULTS

Eighteen patients with CI or ABI collectively underwent a total of 62 MRI scans. Five of 15 (33%) CI patients with magnet had complications: five total of 24 MRI scans (21%). Two patients had magnet removal prior to 29 MRI scans without complications. Four of five MRI-related complications were equipped with a U.S. Food and Drug Administration-approved head wrap. Three of five required a trip to the operating room to explore and reposition the CI magnet; two could not complete MRI secondary to pain. Of the complications, two were Cochlear (Sydney, Australia), two Advanced Bionics (Valencia, CA), and one MED-EL (Innsbruck, Austria). Synchrony model (MED-EL) had 0 of seven complications, with a total of 19 MRI scans, which features a freely rotating and self-aligning magnet.

CONCLUSION

Our series offers a diverse number of CI manufacturers and is in accordance with other literature that CI MRI-related adverse events are occurring at an unacceptable frequency. We can promote CI MRI safety through our institutions' MRI CI patient protocols, raise awareness that diagnostic MRI benefits must outweigh CI-related complications, and advocate for continued industry technological innovation.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:482-489, 2019.

Comparison of MRI in pediatric cochlear implant recipients with and without retained magnet

OBJECTIVE

To report and compare medical, radiological, and audiological outcomes in pediatric cochlear implant recipients who underwent 1.5 and 3 Tesla strength MRI with and without retained magnet.

METHODS

Retrospective chart review at a tertiary care pediatric hospital and review of literature. Patients were identified via electronic medical records database search and were included if they had MRI after cochlear implant.

RESULTS

Of twelve instances of MRI in pediatric cochlear implant recipients at our institution, two minor complications and one major complication were recorded. The rate of complication was equal between patients who underwent MRI with and without retained magnet. All minor complications resulted from MRI with retained magnet whereas the only major complication resulted from magnet removal. Two novel complications are reported, including: magnet removal resulting in silastic tear necessitating reimplantation and magnet dislocation with spontaneous reduction. Magnet removal significantly decreased the size of artifact, but did not alter the diagnostic utility of the MRI. While audiological measures varied chronologically from MRI scans, they did not appear to be appreciably altered by MRI.

CONCLUSION

MRI with and without magnet retention appear to carry risks of both major and minor complications. For the regions of interest for each scan, MRI quality was not appreciably altered by magnet status. Audiological measures appear unaffected by magnet status during MRI however, this may reflect natural variation.

A Rare Complication of Cochlear Implantation After Magnetic Resonance Imaging: Reversion of the Magnet

Cochlear implants are mechanical devices used for patients with severe sensory-neural hearing loss, which has an inner magnet. It is proven that 1.5 Tesla magnetic resonance imaging (MRI) scanners are safe to use in patients with cochlear implant. In our patient, the authors aim to introduce a rare complication caused after a 1.5 Tesla MRI scanning and the management of this situation; the reversion of the magnet of the implant without displacement and significance of surgery in management.

[Factors for Degaussing of a Cochlear Implant Magnet in the MR Scanner]

This study examined the conditions influencing degauss of the magnet using magnetic resonance imaging (MRI). Poly methyl methacrylate (PMMA) was used to fix the measurement magnets to the MRI bed at angles from 0° to 180° for the magnetic flux vector of static magnetic field. The PMMA was moved in the MRI magnetic field. Magnetic flux density was measured before and after bed movement, and the rate of degauss was calculated. The contents examined are as follows: (1) the angle of the magnetic flux vector of the measurement magnets for the magnetic flux vector of the static magnetic field, (2) the number of movements, (3) moving velocity, and (4) the movement on the spatial gradient of magnetic field. Mann-Whitney U test was used for statistical analysis of the data. In conclusion, the effect of the angle of the magnetic flux vector of the implant magnet was high under the conditions of degauss in this study. Therefore, during the MRI examination of a patient with a cochlear implant magnet, the operators identified the directions of the magnetic flux vector and static magnetic field of the implant magnet.

The Safety of MR Conditional Cochlear Implant at 1.5 Tesla Magnetic Resonance Imaging System

In magnetic resonance imaging (MRI) examination of the patients with the cochlear implant, only limited data have a mention for safety information in the instruction manual supplied by the manufacturers. Therefore, imaging operators require more detailed safety information for implant device. We conducted detailed examination about displacement force, torque, and demagnetizing of the cochlear implant magnet based on American Society for Testing and Materials (ASTM) standard using the PULSAR and CONCERTO (MED-EL) with 1.5 tesla MRI system. As a result, the displacement force and the torque of the implant magnet were less than the numerical values descried in the manual. Therefore, these have almost no effect on the body under the condition described in a manual. In addition, the demagnetizing factor of the cochlear implant magnet occurred by a change magnetic field. The demagnetization depended on the direction of a line of magnetic force of the static magnetic field and the implant magnet. In conclusion, the operator must warn the position of the patients on inducing in the magnet room.