Objective: To evaluate the safety and image quality of 1.5-T MRI in patients with cochlear implants and retained internal magnets.
Study Design: Retrospective case series from 2012 to 2014.
Setting: Single tertiary academic referral center.
Patients: All cochlear implant recipients undergoing 1.5-T MRI without internal magnet removal.
Intervention(s): MRI after tight headwrap application.
Main Outcome Measures: Patient tolerance, complications, and characteristics of imaging artifact.
Results: Nineteen ears underwent a total of 34 MRI scans. Two patients did not tolerate imaging with the headwrap in place and required magnet removal before rescanning. One subject experienced two separate episodes of polarity reversal in the same device from physical realignment (i.e., flipping) of the internal magnet requiring surgical repositioning. Three patients were discovered to have canting of the internal magnet after imaging. In all three cases, the magnet could be reseated by applying gentle firm pressure to the scalp until the magnet “popped” back into place. These patients continue to use their device without difficulty and have not required surgical replacement. In patients receiving head MRI, the ipsilateral internal auditory canal and cerebellopontine angle could be visualized without difficulty in 94% of cases. There were no episodes of cochlear implant device failure or soft tissue complications.
Conclusion: Under controlled conditions, 1.5-T MRI can be successfully performed in most patients without the need for cochlear implant magnet removal. In nearly all cases, imaging artifact does not impede evaluation of the ipsilateral skull base. Patients should be counseled regarding the risk of internal magnet movement that may occur in up to 15% of cases, even with tight headwrap application. If internal magnet polarity reversal occurs, a trial of reversing the external magnet can be considered. If canting or mild displacement of the internal magnet occurs, an attempt at reseating can be made by applying gentle firm pressure to the scalp over the internal magnet. If conservative measures fail, the magnet should be surgically repositioned to minimize interruption of device use and to prevent scalp complications.
*Departments of Otolaryngology–Head and Neck Surgery, †Neurologic Surgery, and ‡Radiology, Mayo Clinic School of Medicine, Rochester, Minnesota, U.S.A.
Address correspondence and reprint requests to Matthew L. Carlson, M.D., Department of Otolaryngology–Head and Neck Surgery, Mayo Clinic, 200 First St SW, Rochester, Minnesota, 55905, U.S.A.; E-mail: email@example.com
C.L.W.D. is a consultant for Advanced Bionics Corp., Cochlear Corp., and MED-EL GmbH. No funding or other support was required for this study.
IRB Approval: 14-004344