Magnetic Resonance Imaging of Inner Ear and Internal Auditory Canal Structures in the Presence of a Cochlear Implant

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OBJECTIVE: To determine whether the internal auditory canal (IAC) can be visualized using magnetic resonance imaging (MRI) in users of a cochlear implant (CI) model that can safely undergo MRI at 3 T. PATIENTS: Four normally hearing controls and three individuals unilaterally implanted with a HiRes Ultra 3D (Advanced Bionics LLC, California, USA). INTERVENTIONS: Participants underwent 3 T MRI using sequences appropriate for the postoperative surveillance of the IAC. Images in normally hearing individuals were acquired after placing a fully functional, unpowered, CI underneath a swimming cap at each of eight candidate scalp positions, four on each side of the head. Images were compared to a control condition without a CI present. and CI users were imaged with similar sequences. MAIN OUTCOME MEASURES: In normally hearing controls, the likely impact of the artifact on detection of pathology for multiple neuroradiological locations as rated by two independent radiologists. In CI users, a qualitative assessment of the diagnostic usability of images. RESULTS: Visibility of the ipsilateral IAC and cochlea varied among the three CI users, with images from one participant deemed largely usable, while those from the other two participants exhibited less diagnostic certainty, likely due to differences in implant locations and cranial/neuroanatomical variations. Ratings of images in normally hearing participants showed that more middle-to-anterior CI locations were associated with reduced likelihood of overlooking gross abnormalities. CONCLUSION: Through meticulous surgical placement, bilateral IAC visualization may be achievable for monitoring chronic health conditions such as tumor surveillance in high-risk patients, and as a safety monitoring outcome measure in clinical trials.

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