Beh?et disease (BD) is rare in childhood. We report a 9-year-old boy with neuro-Beh?et disease who presented diplopia and weakness on the left side after a cerebral concussion. Brain magnetic resonance imaging (MRI) revealed hyperintensity of the right mesodiencephalic junction on T2-weighted and fluid attenuated inversion recovery images. Prednisolone administration resulted in complete remission and normalization of abnormal MRI finding. Brain MRI is a useful diagnostic tool when the neurological sign is the first symptom of subclinical BD.