First MRI With New Cochlear Implant With Rotatable Internal Magnet System and Proposal for Standardization of
Nathan D Cass1, Justin M Honce2, Alexandra L O'Dell3
1Department of Otolaryngology.
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.
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