Subacute sclerosing panencephalitis is characterized by the insidious onset of diffuse cerebral dysfunction associated later with myoclonus and typical electroencephalographic changes. The disease progresses relentlessly to coma and death within 2 years. We report a case of acute onset and rapid course associated with atypical CSF, EEG and MRI features simulating acute disseminated encephalomyelitis. Brief review of relevant literature is presented.