AQP4 and neoplastic disease or syndrome: • Presence of at least one typical clinical demyelinating CNS event (e.g., ON, TM, ADEM)• Positive serum MOG-IgG antibody test; borderline titers require supporting radiological or CSF features• Exclusion of alternative diagnoses including MS, AQP4-positive NMOSD, and infectious or neoplastic disorders (1)