Brain and spinal cord atrophy in NMOSD and MOGAD: current evidence and future perspectives.

Neuromyelitis optica spectrum disorder (NMOSD) is a severe form of inflammation of the central nervous system (CNS) including acute myelitis, optic neuritis and brain syndrome. Currently, the classification of NMOSD relies on serologic testing, distinguishing between seropositive or seronegative anti-aquaporin-4 antibody (AQP4) status. However, the situation has recently grown more intricate with the identification of patients exhibiting the NMOSD phenotype and myelin oligodendrocyte glycoprotein antibodies (MOGAD). NMOSD is primarily recognized as a relapsing disorder; MOGAD can manifest with either a monophasic or relapsing course. Significant symptomatic inflammatory CNS injuries with stability in clinical findings outside the acute phase are reported in both diseases. Nevertheless, recent studies have proposed the existence of a subclinical pathological process, revealing longitudinal changes in brain and spinal cord atrophy. Within this context, we summarise key studies investigating brain and spinal cord measurements in adult NMOSD and MOGAD. We also explore their relationship with clinical aspects, highlight differences from multiple sclerosis (MS), and address future challenges. This exploration is crucial for determining the presence of chronic damage processes, enabling the customization of therapeutic interventions irrespective of the acute phase of the disease.