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MRI Without Magnet Removal in Neurofibromatosis Type 2 Patients With Cochlear and Auditory Brainstem Implants

Walton, Joanna*; Donnelly, Neil P.*; Tam, Yu Chuen; Joubert, Ilse; Durie-Gair, Juliette*; Jackson, Cay; Mannion, Richard A.§; Tysome, James R.*; Axon, Patrick R.*; Scoffings, Daniel J.

doi: 10.1097/MAO.0000000000000330
Cochlear Implants

Objective: To assess the impact on image quality of MRI without magnet removal in cochlear implant (CI) and auditory brainstem implant (ABI) users with neurofibromatosis type 2 (NF2).

Study Design: Prospective cohort.

Setting: Tertiary center for cochlear and auditory brainstem implantation.

Patients: Thirteen patients (10 ABI, 3CI) with NF2 underwent a total of 76 MRI scans.

Interventions: MRI without magnet removal.

Main Outcome measure: Ability to visualize the ipsilateral and contralateral cerebellopontine angles (CPAs) and internal auditory meati (IAM) with head MRI.

Results: Of the 76 scans, 40 were of the head, 28 of the spine and 8 of other regions. Scanning was performed with a tight head bandage and plastic card. There were no cases of altered implant function or demagnetization of the device magnet.

A grading system was used to assess the view of the ipsilateral IAM-CPA. In 85% of head scans, the view was unimpaired (Grade 0). In 13%, there was distortion (Grade 1). In 2% (1 case), the view was entirely obscured by artifact (Grade 2). Views of the contralateral CPA and IAM were unimpaired in all cases. The best 3 sequences for the depiction of the ipsilateral IAM-CPA (percent graded as 0) were as follows: axial 3D inversion recovery prepared fast spoiled gradient echo (100%), 2 mm coronal T1W of the IAM-CPA (88.9%), and 2 mm axial T1W of the IAM-CPA (76.9%).

Conclusion: MRI scanning without magnet removal is safe and well tolerated in NF2 patients with auditory implants. With appropriate MRI sequences, the image quality is not significantly impaired.

*Otology and Skull Base Unit, †Cambridge Hearing Implant Program, ‡Department of Radiology, and §Department of Neurosurgery, Cambridge University Hospital, Cambridge, U.K.

Address correspondence and reprint requests to Joanna Walton, M.B.B.S., B.Sc. (Med), M.S., F.R.A.C.S. (ORL-HNS), ENT Department, Clinic 10, Box 48 Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0QQ, ENT Department, Addenbrookes Hospital, Cambridge; E-mail: drjoannawalton@gmail.com

The authors disclose no conflicts of interest.

Copyright © 2014 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company