Introduction: Axon pathology in multiple sclerosis is an emerging concept, not because it is unknown but because it has been forgotten. However, clinical, functional and pathological aspects have clearly shown that it is damaged at a very early stage in development of the plaque of demyelination. There is sufficient clinical, radiological and pathological evidence to permit definition of axonal damage as the central element of the pathology and clinical features of multiple sclerosis.
Development and conclusions: Throughout this article we will see how the axon is affected in multiple sclerosis, how this affects the inflammatory response and which parameters allow us to measure axonal damage and its relation to disability. Finally we will see how a new physiopathogenic concept of multiple sclerosis appears, based on the axonal lesion, and how this fits current clinico-pathological concepts better.