الفهرس 
AnatomyOnly 14 pages are availabe for public view
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Abstract
Demyelinating diseases are a group of diseases which involve damage to, and destruction of myelin sheaths that surround many nerve fibres. The axons of these fibres may be damaged as well. The mechanism of myelin damage may be different in different diseases, but they have been grouped together under the general term of ”demyelinating diseases”. They are predominantly white matter diseases and the demyelination is often perivenous. A well-demarcated area of demyelination is known as a ”plaque”. They often show a predilection for the subependymal region and the area beneath the pia mater, which covers the surface of the brain. The blood vessel within the centre of the area of demyelination is usually patent. The group of diseases associated with specific metabolic defects influencing the formation of myelin have now been separated under the general term “dysmyelinating disorders or leukodystrophies”.
Demyelination can be regarded as either primary or secondary, the primary form destroys or damages myelin or myelin-forming cells and axons are relatively normal, at least in the early stages, the primary demyelinating diseases are multiple sclerosis and its variants, neuromyelitis optica and monophasic disorders as: optic neuritis, acute transverse myelitis, acute disseminated encephalomyelitis, and acutehemorrhagic leukoencephalitis & While the secondary form in which myelin destruction occurs as a secondary phenomenon and usually show a pattern that is not particularly perivenous, the secondary demyelinating diseases are: Marchiafava-Bignami, central pontine myelinolysis, leukodystrophies, vitamin B12 deficiency, and progressive subcortical ischemic demyelination.
The range of causes is wide and includes various virus infections, immunological disorders, nutritional or metabolic disorders, toxins (including some used in therapy such as anti-mitotic agents and radiotherapy), genetic factors, and following prolonged oedema or hypoxia.
In recent decades, the use of neuroimaging techniques has resulted in outstanding progress in the diagnosis and management of neurological diseases, and this is particularly true of those diseases that affect the white matter of the brain and spinal cord, as there is marked overlap in the clinical presentation of the demyelinating diseases, they can clearly be distinguished by neurological investigations including: neurophysiologic, neuroimaging and laboratory investigation, therefore, the diagnosis depends upon a mixture of clinical and pathological features.
Neuroimaging studies provide important insights into the white matter diseases. MR imaging is exquisitely sensitive for detecting brain abnormalities. Particularly in the evaluation of demyelinating diseases.