MRI in patients with auditory implants equipped with implanted magnets-an update : Overview and procedural management

Abstract

More than 100,000 patients with cochlear implants live in Germany. In addition, numerous patients have auditory bone conducted, middle-ear conducted or brainstem conducted implants equipped with implanted magnets. At the same time, the number of patients being examined by magnetic resonance imaging (MRI) is increasing. Therefore, MRI compatibility of these implants is an essential quality feature. This article provides information about technical innovations and new auditory devices since November 2013 that have medical-technical certification in the European Union and the USA. We communicate the restrictions of the manufacturers and aselective literature search in PubMed using the following keywords: MRI compatibility/MRI safety + cochlear implant/auditory brainstem implant/Bonebridge/Sophono alpha/Vibrand Soundbridge/BAHA attract. We included all publications of this search concerning MRI compatibility of hearing implants complemented by papers cited in the primary articles. In rare cases, high electromagnetic field intensities as used in MRI can cause shearing movements up to dislocation of the implant or the magnet of the device. As aresult the implant function could fail. Image artifacts in head MRIs can be reduced by using appropriate MRI sequences. Nevertheless, possible artifacts and the hereby reduced validity of the skull MRI results have to be considered when indicating the examination. Meanwhile, all innovations of these auditory devices are licensed to 1.5 T MRI examination, some implants up to 3.0 T MRI magnetic field intensity. For older devices, the necessary safety measures listed in the article published by Nospes, Mann and Keilmann in November 2013 should be used. Respecting the manufacturer's instructions, MRI scans without removal of the magnet in patients with these auditory implants is safe. However, due to possible defects/dislocations of the implant that may occur and the reduced quality of the skull MRI images, the indication for MRI in devices with MRI certification should only be performed under close consultation between the investigating physicians, the implanting team supervising the patient and the radiologist. All other possible diagnostic procedures should be exhausted first.