leukoencephalitis
noun
leu·ko·en·ceph·a·li·tis
variants:
or chiefly British leucoencephalitis \ ˌlü-kō-in-ˌsef-ə-ˈlīt-əs 
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plural leukoencephalitides\ -ˈlit-ə-ˌdēz
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Medical Definition of leukoencephalitis
: inflammation of the white matter of the brain