<prompt> Progressive multifocal leukoencephalopathy sparesWhite matter of cerebrumWhite matter of parietal lobeWhite matter of periventricular areaSpinal cord and optic nerve  <response>: Progressive multifocal leukoencephalopathy PML is a demyelinating disease which results from the reactivation of John Cunningham virus JC virus infecting oligodendrocyteswhich provide suppo and insulation to axons in CNS The term Leukoencephalopathy refers to all of the brain white matter diseases Toxic leukoencephalopathy or toxicspongiform leukoencephalopathy is a rare condition that is characterized by progressive damage -pathy to white matter -leuko- in the brain -encephalo-, paicularly myelin, due to causes such as exposure to drug abuse, environmental toxins, or chemotherapeutic drugs 