Multi-Magnet Cochlear Implant Technology and Magnetic Resonance Imaging: The Safety Issue.

Despite the spread of novel-generation cochlear-implant (CI) magnetic systems, access to magnetic resonance imaging (MRI) for CI recipients is still limited due to safety concerns. The aim of this study is to assess and record the experiences of Hires Ultra 3D (Advanced Bionics) recipients who underwent an MRI examination. A multicentric European survey about this topic was conducted focusing on safety issues, and the results were compared with the current literature. We collected a total of 65 MRI scans performed in 9 otologic referral centers for a total of 47 Hires Ultra 3D recipients, including, for the first time, 2 children and 3 teenagers. Preventive measures were represented by scanning time and sedation for children. Head wrapping was used in eight cases, and six of the eight cases received local anesthesia, even if both measures were not needed. Only three patients complained of pain (3/65 examinations, 4.6%) due to the tight head bandage, and one of the three cases required MRI scan interruption. No other adverse events were reported. We believe that these results should encourage MRI execution in accordance with manufacturer recommendations for Ultra 3D recipients.

Advanced Bionics HiRes Ultra and Ultra 3D Series Cochlear Implant Recall: Time Course of Anomalies.

OBJECTIVES: To estimate median survival time until the appearance of anomalies indicating a potential implant failure associated with fluid ingress in implanted cochlear implant (CI) devices of the initial version of Advanced Bionics HiRes Ultra and HiRes Ultra 3D series. STUDY DESIGN: Retrospective review. METHODS: Cochlear implantation was performed in a standard fashion. Implant integrity was tested at follow-up visits by measuring impedance and electrically evoked compound action potential (ECAP). Additional tests such as electrical field imaging (EFI) were conducted by the manufacturer. Based on these tests, the presence or absence of an anomaly was classified. RESULTS: Of the 349 devices implanted at this institution, 181 showed anomalies in accordance with the special failure mode and for this reason, 120 implants were already explanted. The median survival time without anomalies was 1062 days. So far, the suspicion of device failures has been confirmed in all cases in which a post-implantation analysis was already available. CONCLUSIONS: Regular tests at the follow-up visits are necessary to monitor the integrity of CIs. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:2484-2490, 2022.

MRI-induced artifact by a cochlear implant with a novel magnet system: an experimental cadaver study.

PURPOSES: To primarily evaluate MRI-induced effects for Ultra 3D cochlear implantation in human cadavers in terms of artifact generation and MR image quality. METHODS: Three human cadaveric heads were submitted to imaging after unilateral and bilateral cochlear implantation. The 1.5 T MR examination protocol was chosen in accordance with our institutional protocol for the assessment of brain pathology. The maximal signal void size was measured according to each sequence and plane. Two experienced neuro-radiologists and one experienced otoneurosurgeon independently evaluated the MR image quality findings. A 4-point scale was used to describe the diagnostic usefulness of 14 brain structures. RESULTS: Shape and size of the artifacts were found to be highly related to MRI sequences and acquisition planes. MRI sequences and processing algorithms affected the ability to assess anatomical visibility. Image quality appeared either high or assessable for diagnostic purposes in 9 out of 14 of the ipsilateral structures, in at least one plane. Anatomical structures contralateral to the cochlear implant were highly visible in all conditions. Artifact intrusion clearly improved after application of metal artifact-reduction techniques. In the case of bilateral cochlear implant, a mutual interaction between the two implant magnets produced an additional artifact. CONCLUSIONS: We performed the first cadaver study aimed at systematically evaluating the MRI-induced artifacts produced by a cochlear implant with a novel four bar magnet system. Specific brain structures can be assessable for diagnostic purposes under 1.5 T MRI, with the cochlear implant magnet in place.