Multiple sclerosis is an autoimmune demyelinating disease of the central nervous system that leads to a progressive deterioration of the neurological functions. The concept of primary myelin and oligodendrocyte damage with axon sparing (axon-myelin dissociation) has been recently reconsidered with the demonstration that neuro-axonal lesions are an early phenomenon, linked to the inflammatory process, observed outside demyelinated areas, and correlated with the progression of the disease. Neurodegeneration in MS, long considered as a late process following recurrent episodes of demyelination, is now accepted as an early and major trigger of MS pathogenesis on which research should focus in the