Abnormal cochlear enhancement in Norrie disease.

Norrie disease (ND) is a rare x-linked disease with retinal and cochlear vascular abnormalities. Clinically, it is characterized by congenital blindness and progressive sensorineural hearing loss during adolescence. We present images of a 3 year old child with ND and normal hearing demonstrating bilateral cochlear enhancement on brain MRI, a finding which has not been previously reported. ND mouse models show progressive degeneration of the endolymph-producing stria vascularis (SV); we hypothesize that these changes allow gadolinium leakage into the endolymph. Our images indicate that cochlear enhancement precedes changes in hearing and suggest that temporal bone/internal auditory canal MR imaging should be considered in the evaluation of ND. Future studies are needed to characterize the temporal evolution of this cochlear enhancement and how it corresponds with hearing loss. Mouse models suggest that it may be a transient phenomenon and diminish as the SV degenerates further. As ND gene therapy trials approach clinical use, cochlear enhancement could aid candidate selection and provide insight into treatment effect.