Magnetic resonance imaging at 1.5 T after cochlear implantation

To assess the safety of 1.5 T magnetic resonance imaging (MRI) in patients with cochlear implants (CIs) with internal magnets.

Retrospective review of CI patients who underwent an MRI at Johns Hopkins.

Sixteen patients with a mean age of 43 ± 22 years with a CI underwent a total of 22 clinically indicated 1.5 T MRI. Devices from 3 major CI manufactures were represented.

Binding of CI with mold material and gauze was performed before MRI. Some patients were also administered a sedative. Intravenous gadolinium contrast was used in all but 1 patient.

Patients were assessed with regard to the ability to complete the MRI, the size of the artifact caused by the device, the ability to make a diagnosis from the studies, the post-MRI CI function, and the magnet's position.

No CI malfunction, displacement, or magnet displacement was observed after MRI. One patient was unable to tolerate the procedure because of pressure at the site of the device. One patient required intravenous sedation to complete the study. The CI generally produced an artifact on brain MRI, with a mean maximal anterior-posterior dimension of 6.6 cm and a lateral dimension of 4.8 cm around the site of the device. The contralateral internal auditory canal was visualized in all patients, and the ipsilateral internal auditory canal was at least party visible in all but 1 patient.

Patients can safely undergo 1.5 T MRI after CI if the device is tightly bound before scanning. Magnet displacement was not observed, and we think the risk to be minimal compared with the risk and inconvenience of removing the magnet before the study.