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

Abstract

BACKGROUND\nMore 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.\n\n\nMETHODS\nThis 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 a\xa0selective literature search in PubMed using the following keywords: MRI compatibility/MRI safety\u202f+\u2009cochlear 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.\n\n\nRESULTS\nIn 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 a\xa0result 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\u202fT MRI examination, some implants up to 3.0\u202fT 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.\n\n\nCONCLUSION\nRespecting 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.