Imaging of the visual pathway in optic neuritis

Author(s): Pfueller Caspar

Optic Neuritis (NMO, Devic syndrome) is a rare autoimmune inflammatory disease of the Central Nervous System (CNS) that is clinically characterized by primarily severe damage to the optic nerve and spinal cord. For a long time, NMO was considered a variant of Multiple Sclerosis (MS). However, recent mounting evidence points to a distinct pathogenesis. An important step was the discovery of a highly specific biomarker for NMO, the so-called NMO-IgG, whose target antigen turned out to be Aqua Porin-4 (AQP4) of the most abundant water channel in the body central nervous system. Since then, various tests for the detection of anti-AQP4 antibodies have been developed, which facilitate the differentiation of NMO from clinically relevant MS. Anti-AQP4 antibodies are detectable in 60-90% of NMO patients with a specificity of 91-100%. Contrary to previous belief, NMO is now considered a relapsing disease in 80-90% of patients. With the discovery of AQP4 antibodies, the clinical spectrum of NMO has expanded and now AQP4-Positive Persistent Transverse Myelitis (LETM) and AQP4-positive Recurrent Optic Neuritis are considered is part of the NMO Spectrum Disorders (NMOSD).