The main objective of this study was to evaluate the frequency of anti-AQP4 Ig G in patients with idiopathic inflammatory demyelinating diseases such as NMO and high risk syndromes for neuromyelitis optica spectrum disorder (NMOSD) such as monophasic or multiphasic recurrent transverse myelitis and optic neuritis as well as brain lesions at onset of disease either monophasic/multiphasic, monofocal, or multifocal. Here, GAN is linked to neuromyelitis optica.