AQP4 and myeloid sarcoma: First, MRI facilitates diagnosis, with differentiation of NMOSD from MS, MOGAD, and other mimics in combination with serologic testing for AQP4 and MOG antibodies, preferably by employing cell-based assays.18,19 Second, MRI findings such as spinal cord atrophy, and spinal cord and optic nerve lesion length, may provide prognostic information about NMOSD disease course20, , , –24 to help direct optimal therapy including institution of newer high-efficacy therapies.