Performing MRI Scans on Cochlear Implant and Auditory Brainstem Implant Recipients: Review of 14.5 Years Experience.

OBJECTIVE: To assess the complication rate of magnetic resonance imaging (MRI) using 1.5 T scanners on cochlear implant (CI) and auditory brainstem implant (ABI) recipients over 14.5 years. METHODS: Prospective study conducted in a tertiary referral center for cochlear and auditory brainstem implantation, including patients with neurofibromatosis 2. The primary outcome was complications related to MRI scanning in implant recipients, including failure to complete MRI sessions. The secondary outcome was magnet void size due to MRI scanning with magnet in situ. RESULTS: Ninety-seven patients (21 ABI recipients, 76 CI recipients of whom 23 were bilateral) underwent a total of 428 MRI sessions consisting of 680 MRI procedures, which generated 2,601 MRI sequences (excluding localizers). Of these, 28/428 (6.5%) MRI sessions were performed with magnet removed, and the remaining 400/428 (93.4%) with the magnet in situ. The overall complication rate per session was 15/428 (3.5%). The majority of complications were accounted for by patient discomfort, in some cases requiring abandoning the scan session, but 5 magnet dislocations were also recorded. There were no cases of implant device failure or excessive demagnetization of the receiver stimulator magnet.For CI and ABI recipients, the implant caused large voids of around 110 mm × 60 mm with the magnet in situ which reduced to 60 mm × 30 mm when the magnet was removed. However, it was usually possible to visualize the internal acoustic meatus and cerebellopontine angle by positioning the implant package higher and further forward compared with conventional positioning. CONCLUSION: MRI scanning in ABI and CI recipients is generally safe and well tolerated without magnet removal, and carries a low rate of complications. However, patients should be fully informed of the possibility of discomfort, and precautions such as local anesthetic injection and head bandaging may reduce the likelihood of adverse events.

MRI without magnet removal in neurofibromatosis type 2 patients with cochlear and auditory brainstem 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.