Cortical gray matter lesions in multiple sclerosis

Abstract Multiple sclerosis (MS) and neuromyelitis optica (NMO) are the two main autoimmune and inflammatory diseases of the central nervous system. MS is considered an 'oligodendrocytopathy' with undefined autoantibodies, whereas NMO is considered an 'astrocytopathy' with aquaporin-4 antibodies. Both have long been considered autoimmune diseases that primarily affect the white matter (WM). However, recent interest in gray matter (GM) pathology is emerging. Pathological evaluations reveal that substantial cortical demyelination is prominent at all stages or courses of MS. In addition, the neurodegeneration in MS is present not only in GM demyelination but also in normal-appearing GM. NMO involves cortical neurodegeneration and unique dynamics of astrocytes; however, no cortical demyelination is seen. Thus, MS and NMO are distinct diseases with unique pathological features in the brain WM and GM. Although the cause of GM and WM lesions in MS and NMO has not been fully determined, improved knowledge about the pathomechanisms in affected brains is desired. This would result in a more targeted pharmacotherapeutic approach to these diseases.