Leukoencephalopathy

A CT demonstrating leukoencephalopathy most likely due to small vessel ischemia. Arrow marks just one of many areas.

The term Leukoencephalopathy is a broad term for leukodystrophy-like diseases.^[1] It is applied to all brain white matter diseases, whether their molecular cause is known or not. It can refer specifically to any of these diseases:

• Progressive multifocal leukoencephalopathy
• Toxic leukoencephalopathy
• Leukoencephalopathy with vanishing white matter
• Leukoencephalopathy with neuroaxonal spheroids
• Reversible posterior leukoencephalopathy syndrome
• Megalencephalic leukoencephalopathy with subcortical cysts. It can also refer to gene MLC1 or Megalencephalic leukoencephalopathy with subcortical cysts 1, a human gene related to the former disease.
• Hypertensive leukoencephalopathy

The classification of leukoencephalopathies is a matter of debate. Some authors divide leukoencephalopathies into hereditary disorders and acquired disorders. The hereditary demyelinating disorders are then classified according to the localization of the underlying metabolic defect, and they include the Leukodystrophies when myelin growth is the underlying problem.

The acquired demyelinating disorders are classified according to their underlying causes into five groups: noninfectious–inflammatory, infectious–inflammatory, toxic–metabolic, hypoxic–ischemic (vascular problems like Binswanger's disease), and traumatic.^[2]

This classification is diffuse sometimes. For example CADASIL is at the same time hereditary and hypoxic.

References

1. Lyon, G.; Fattal-Valevski, A.; Kolodny, E. H. (2006). "Leukodystrophies". Topics in Magnetic Resonance Imaging 17 (4): 219–242. doi:10.1097/RMR.0b013e31804c99d4. PMID 17414998.
2. Marjo S. van der Knaap and Jaap Valk, eds. New York: Springer; 2005, Magnetic Resonance of Myelination and Myelin Disorders, 3rd ed.