Changes observed in multiple sclerosis using magnetic resonance imaging reflect a focal pathology distributed along axonal pathways.

Multiple sclerosis has long been recognized as a multifocal inflammatory demyelinating disease of the central nervous system. The fact that patients with multiple sclerosis can develop a secondary progressive phase of their disease which is resistant to anti-inflammatory therapies, together with the fact that brain atrophy can develop in patients with a relatively low volume of white matter lesions, has led to suggestions that multiple sclerosis may be a degenerative disease. However, primary degenerative disorders are not usually associated with recurrent episodes of inflammatory demyelination. Support for neurodegeneration in MS being associated with focal lesions comes from topographical mapping of the spatial relationship of axonal injury and tissue loss to lesions using advanced image analysis methods.