The evolution of criteria for assessing disease activity and progression in multiple sclerosis (or the "saga of acronyms").

Therapeutic advances in multiple sclerosis have led to the evolution of criteria used to assess disease activity and progression. The concept of NEDA aims for the complete absence of clinical and radiological activity but is very strict and difficult to sustain. MEDA was proposed as a more realistic goal, allowing minimal disease activity. Disability progression can no longer be assessed using the EDSS alone, leading to the development of composite measures such as NEP and NEPAD. Studies have shown that most disability worsening occurs independently of relapses, giving rise to the key concept of PIRA, and then PIRMA. This silent progression begins early and is driven by neurodegenerative and chronic inflammatory mechanisms. New concepts (SAW) further characterize this slow progression. An integrated framework separating inflammatory activity (NEIDA) from smouldering progression (NESDA) is now proposed to better guide therapeutic strategies.