Acute demyelinative lesions

In the CNS, the major demyelinating disorder is multiple sclerosis (MS). MS should be differentiated from other disorders in which the histologic appearance of the lesions and the relapsing and remitting clinical course are similar. Acute MS lesions, in addition to plentiful foamy macrophages with increased proteases, have perivascular FCA-positive lymphocytes, EMA-positive and... 

A number of animal diseases caused by viruses involve primary demyelination and often are associated with inflammation. These diseases are studied as animal models, which may provide clues about how a viral infection could lead to immune-mediated demyelination in humans [1, 5, 6]. Canine distemper virus causes a demyelinating disease, and the lesions in dog brain show a strong inflammatory response with some similarities to acute disseminated encephalomyelitis in man [ 1 ]. Visna is a slowly progressive demyelinating disease of sheep caused by a retrovirus [ 1 ]. 

The classic example of demyelination of the CNS is multiple sclerosis (MS), in which a chronic inflammatory lesion is characterised by a sharply demarcated plaque containing preserved axons denuded of myelin. Demyelination also occurs in infectious diseases such as progressive multifocal leucoencephalopathy and acute disseminated leucoencephalitis, but it is the disseminated focal form of MS that will be addressed in this review article. 

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