n. inflammation of the brain. It may be caused by a viral or bacterial infection or it may be part of an allergic response to a systemic viral illness or vaccination (see encephalomyelitis). Viral encephalitis is endemic in some parts of the world; it may also occur epidemically or sporadically. One form – encephalitis lethargica – reached epidemic proportions shortly after World War I and was marked by headache and drowsiness, progressing to coma (hence its popular name – sleepy sickness). Encephalitis can cause postencephalitic parkinsonism. Another type of encephalitis that occurs sporadically is due to the herpes simplex virus.
Subjects: Medicine and health