AQP4 and encephalitis: Brain MRI features suggestive of encephalitis was seen in 39%–46% of the patients, but the HIS score was not associated with MRI abnormalities, suggesting that factors other than high CSF ab titers, such as concurrent abs against MOG, AQP4, GFAP (19, 26), or other surface antigens not identified, or T-cell-mediated injury may contribute to MRI abnormalities.