AQP4 and neuromyelitis optica: On day 13, serum AQP4-immunoglobulin G (IgG)) was found to be strongly positive (titers > 75 U/ml), thus fulfilling the diagnostic criteria of NMO with AQP4-IgG.8 The patient could not even brush her teeth on day 6 but was able to eat her meals without assistance on day 13.