a fulminating demyelinating disorder of the central nervous system that affects mainly children and young adults. Almost always preceded by a respiratory infection, characterized by the abrupt onset of fever, headache, confusion, and nuchal rigidity, soon followed by focal seizures, hemiplegia, or quadriplegia, brainstem findings, and coma; the CSF shows evidence of an inflammatory process; due to the massive destruction of the white matter of one or both hemispheres, often accompanied by similar destruction of the white matter of the brainstem and cerebellar peduncles; of unknown etiology. Syn: acute hemorrhagic leukoencephalitis, acute necrotizing hemorrhagic leukoencephalitis.