MRI during cochlear implant assessment: Should we image the whole brain?

OBJECTIVES: Magnetic resonance imaging (MRI) is a standard part of a cochlear implant assessment in most centres. While there is ample literature on the temporal bone-specific imaging that is required, the role of whole brain imaging has not been as fully studied. We present the first report of the incidence of associated brain abnormalities in the whole cochlear implant population, including adults and consider their significance.

METHODS: We retrospectively reviewed 51 (12 adults and 39 children) sequential cases since we added whole brain MRI sequences to our cochlear implant assessment protocol. We reviewed the scans for abnormalities of the cochlea and cochlear nerve and a neuroradiologist reviewed the images of the whole brain sequences for further abnormalities.

RESULTS: We identified abnormalities on the whole brain sequences in 21 (41%) of these patients, 5 of 12 adults (42%) and 16 of 39 children (41%). Thirty-six (71%) patients subsequently had at least one implant inserted, 13 with abnormalities on whole brain MRI (36%) and 23 without. Of the 15 patients who did not undergo subsequent implantation, 8 had positive findings on their whole brain MRI sequence (53%). There was no statistical difference in the probability of finding an abnormality on the whole brain MRI between those who did and those who did not go on to have an implant (P = 0.35). There were abnormalities within the inner ear in five patients.

DISCUSSION: The abnormalities detected on the whole brain images are heterogenous and of wide ranging clinical significance ranging from truly incidental findings to abnormalities that are so severe that they may predict a very poor prognosis such that an implant may contribute little.