However, we think that the present patient may not have NMOSD, because of the following reasons: 1) anti-AQP-4 IgG was seronegative; 2) a mildly elevated IgG index also supports ADEM, because the IgG index value is typically not elevated in NMOSD; 3) most core clinical features necessary to fulfill NMOSD were lacking, such as optic neuritis, area postrema syndrome (hiccup, nausea and vomiting), narcolepsy or acute diencephalic syndrome, or acute brainstem syndrome. Here, AQP4 is linked to optic neuritis.