الفهرس 
Biology and Structure of the White MatterOnly 14 pages are availabe for public view
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Abstract
Pediatric white matter disorders are complex, numerous and result from a vast array of causes ranging from white matter injury or inflammation to congenital metabolic disorders.
Virtually all categories of pathology may cause white matter abnormalities. White matter abnormalities may be seen in congenital, inflammatory, neoplastic, posttraumatic, metabolic, toxic, vascular, degenerative and demyelinating diseases. The primary white matter disorders are classically divided into two groups: dysmyelinating disorders (usually metabolic), in which normal myelin fails to form, and the demyelinating diseases, in which normal myelin has formed and is later destroyed by a myelinoclastic process.
Leukoencephalopathies constitute a large group of inherited and acquired diseases that predominantly involve the cerebral white matter. The enzyme defects leading to dysfunction and breakdown of myelin have been identified in an increasing number of genetic leukoencephalopathies that have their onset in infancy or childhood. Nevertheless, approximately 30% of leukoencephalopathies remain of unknown etiology, despite extensive clinical, imaging, and laboratory investigations.
Two main pathophysiologic mechanisms may affect myelin and lead to white matter abnormalities. “Hypomyelination” is defined as a deficit in the formation of myelin, whereas “demyelination” is defined as loss or destruction of previously formed myelin.
In order to diagnose these disorders laboratory investigations should include hormonal,amino acids and fatty acids levels while radiologically MR imaging is highly sensitive in determining the presence and assessing the severity of underlying white matter abnormalities in patients with leukodystrophy. Although the findings are often nonspecific, systematic analysis of the finer details of disease involvement may permit a narrower differential diagnosis, which the clinician can then further refine with knowledge of patient history, clinical testing, and metabolic analysis. MR imaging has also been extensively used to monitor the natural progression of various white matter disorders and the response to therapy.
Depending on the type of leukodystrophy and the symptoms, treatment may include: Medications, Physical, occupational, and/or speech therapy, Nutritional programs, Education and Recreational programs
Haematopoietic stem cell transplantation: In a few of the leukodystrophies (as lysosomal storage diseases and adrenoleukodystrophy), HSCT with bone marrow, cord blood, peripheral blood, or certain fetal tissues may help stop the progression of the disease. Disease phenotype and the extent of disease at the time of transplantation are of fundamental importance in determining outcomes.
Enzyme replacement therapy: Replacement of the abnormal or absent enzyme is being explored for a few of the leukodystrophies. Research is being done in this area.
Gene therapy: gene therapy strategy aiming at transferring the disease gene into autologous hematopoietic stem cells using lentiviral vectors has been developed and has already entered into the clinics for X-linked adrenoleukodystrophy and metachromatic leukodystrophy. Long-term follow-up has shown that hematopoietic stem cells gene therapy can arrest the devastating progression of X-linked adrenoleukodystrophy.
Researches should continue to support the effectiveness and clear the outcome of all these recent modalities of treatment.