<unk> . Its sequelae and treatment – Constantin Von Economo, 1931: front page The causes of<unk>  are uncertain. Some studies have explored its origins in an autoimmune response, and, separately or in relation to an immune response, links to pathologies of infectious disease – viral and bacterial, e.g., in the case of influenza, where a link with encephalitis is clear. Postencephalitic Parkinsonism was clearly documented to have followed an outbreak of<unk>  following the 1918 influenza pandemic; evidence for viral causation of the Parkinson's symptoms is circumstantial (epidemiologic, and finding influenza antigens in<unk>  patients), while evidence arguing against this cause is of the negative sort (e.g., lack of viral RNA in postencephalitic Parkinsonian brain material). In reviewing the relationship between influenza and<unk>  (EL), McCall and coworkers conclude, as of 2008, that "the case against influenza is less decisive than currently perceived… there is little direct evidence supporting influenza in the etiology of EL," and that "almost 100 years after the EL epidemic, its etiology remains enigmatic." Hence, while opinions on the relationship of<unk>  to influenza remain divided, the preponderance of literature appears skeptical. The German neurologist Felix Stern, who examined hundreds of<unk>  patients during the 1920s, pointed out that their<unk>  typically evolved over time. The early symptoms would be dominated by sleepiness or wakefulness. A second symptom would lead to an oculogyric crisis. The third symptom would be recovery, followed by a Parkinson-like syndrome. If patients of Stern followed this course of disease, he diagnosed them with<unk> . Stern suspected<unk>  to be close to poliomyelitis, without evidence. Nevertheless, he experimented with the convalescent serum of survivors of the first acute syndrome. He vaccinated patients with early-stage symptoms, telling them that it might be successful. Stern is author of the definitive 1920s book, Die Epidemische Encephalitis. In 2010, in a substantial Oxford University Press compendium reviewing the historic and contemporary views on EL, its editor, Joel Vilensky, of the Indiana University School of Medicine, quotes another researcher, writing in 1930, who states, "we must confess that etiology is still obscure, the causative agent still unknown, the pathological riddle still unsolved…", and goes on to offer the following conclusion, as of that publication date:Subsequent to publication of this compendium, an enterovirus was discovered in<unk>  cases from the epidemic. In 2012, Oliver Sacks, the author of the book "Awakenings", about institutionalized survivors, acknowledged this virus as the probable cause of the disease. Other sources have suggested Streptococcus pneumoniae as a cause.
Encephalitis lethargica
Japanese encephalitis
Powassan encephalitis
Eastern equine encephalitis
Saint Louis encephalitis
Brain fever
Tick-borne encephalitis
Limbic encephalitis