Leukoencephalopathy (leukodystrophy-like diseases) is all of the 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. [Source: Wikipedia ]