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Purpose: A new generation of cochlear implant (CI) magnets and specific surgical techniques (e.g., implant positioning) has changed the relationship between a CI and magnet resonance imaging (MRI). MRI allows a pain free in vivo evaluation of the inner ear fluid state and internal auditory canal after the insertion of an electrode. The aim of this study is to evaluate how the patient's head position in the MRI scanner influences the CI magnet-related artefact. Methods: We performed in vivo measurement of MRI artefacts at 3 T with a CI system containing a bipolar diametrical magnet. The implant magnet was positioned with a head bandage at different positions from the nasion and external auditory canal in three volunteers. We used a turbo spin echo (TSE) T2w sequence on the axial and coronal planes and observed three positions: (1) regular position, (2) chin to chest (anteflexion), and (3) hyperextension (retroflexion). Results: By comparing the positions, anteflexion of the cervical spine in a chin-to-chest position allowed us to place the artefact in a more apical position from the IAC in the coronal plane. The hyperextension of the cervical spine position shifts the artefact father towards the cochlea's direction. Conclusion: The head's position can influence the location of MRI artefacts. In cases where the artefact diminished the IAC or cochlea, anteflexion of the cervical spine in the chin-to-chest position of the head in the MRI scanner should be attempted to allow a visualization of the IAC. [ABSTRACT FROM AUTHOR]

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Cochlear implant surgery has become a successful procedure for deaf patients to restore their hearing again. Some of the patients, however, complain of persisting dizziness after the surgery which can have a major impact on their quality of life. Neurotological tests of the vestibular system were applied in a total of 18 cochlear implantees pre- and postoperatively. In addition, vestibular evoked myogenic potentials were evoked intraoperatively to investigate possible interferences of the electrically stimulated cochlear implant electrode (eVEMP) with vestibular receptor cells of the saccule in more detail. After cochlear implantation, the saccular function was impaired in the majority of the patients. However, eVEMPs could be recorded intraoperatively in all patients by intracochlear, high-level electrical stimulation via the cochlear implant electrode. In essence, acute, short-term dizziness after cochlear implantation seems to result primarily from a transient vestibular deficit of various origins. In contrast to this, chronic, persisting dizziness after cochlear implant surgery is largely based on a dysfunction of the saccular macula which is an integral component of the otolith system. This saccular impairment is induced most likely by the insertion trauma of the cochlear implant electrode when advancing it into the inner ear. A possible coactivation of the inferior vestibular nerve by the electrical stimulation might play an additional role in the pathogenesis of the persisting postsurgical dizziness. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]