Identification of Auditory Brainstem Paddle Migration Arising from Fat Atrophy Utilizing MRI

Objective To demonstrate magnetic resonance imaging's (MRI's) utility in investigating auditory brainstem implant (ABI) performance degradation. Design Case study. Setting Academic medical center. Participant This report presents a patient with neurofibromatosis type 2 and an ABI with durable, limited open-set speech who developed nonauditory side effects and a complete lack of auditory perception. ABI paddle placement was assessed with 1.5 Tesla (T) Siemens MRI, and device function was assessed utilizing integrity tests. Main Outcome Measure The etiology of ABI performance degradation utilizing 1.5 T Siemens MRI. Results On initial postoperative 1.5 T Siemens MRI, the ABI paddle approximated the cochlear nucleus. Approximately 1 year later, the patient experienced ABI performance degradation and dizziness. Although ABI device integrity testing was normal, follow-up 1.5 T Siemens MRI revealed lateral ABI paddle migration from the foramen of Luschka toward the flocculus, likely due to observed fat atrophy from the prior craniotomy reconstruction, suggesting a possible etiology for the observed ABI degradation. Conclusion This report presents MRI's ability to successfully delineate postoperative fat atrophy, ABI paddle migration in relation to the brainstem, and residual tumor in a patient with ABI degradation.