Lesional demyelinations of the central nervous system

Multiple sclerosis and other demyelinating diseases of the central nervous system (CNS) produce lesions (demyelinated areas in the CNS) and glial scars or scleroses. They present different shapes and histological findings according to the underlying condition that produces them. Demyelinating diseases are traditionally classified in two kinds: demyelinating myelinoclastic diseases and demyelinating leukodystrophic diseases. In the first group a normal and healthy myelin is destroyed by a toxic, chemical or autoimmune substance. In the second group, myelin is abnormal and degenerates. The second group was denominated dysmyelinating diseases by Poser Therefore, since Poser demyelinating diseases normally refers to the myelinoclastic part. Demyelinating diseases of the CNS can be classified according to their pathogenesis into five non-exclusing categories: demyelination due to inflammatory processes, viral demyelination, demyelination caused by acquired metabolic derangements, hypoxic–ischaemic forms of demyelination and demyelination caused by focal compression. The four non-inflammatory possibilities are: viral demyelination, metabolic demyelination (Leukodystrophy and its sub-conditions, Adrenoleukodystrophy and Adrenomyeloneuropathy ), hypoxic–ischaemic forms of demyelination (Susac's syndrome, leukoaraiosis) and, demyelination caused by focal compression. All these four types of demyelination are non-inflammatory and different to MS even if some leukoencephalopathies can produce similar lesions Idiopathic inflammatory demyelinating diseases Typical lesions are similar to those of MS, but there are four kinds of atypical inflammatory demyelinating lesions: Ring-like (antibody-mediated), megacystic (tumefactive), Balo-like, and diffusely-infiltrating lesions. The list of the diseases that produce CNS demyelinating lesions is not complete, but it includes: Standard multiple sclerosis, the most known and extended variant.