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Symptoms are initially that of pharyngitis followed by lethargy, extrapyramidal movements (parkinsonism and dyskinesias), neuropsychiatric
disturbance (obsessive, compulsive disorder, catatonia, mutism, apathy and conduct disorders), and ocular movement disorder (oculogyric crises).
The exact etiology is unknown, but there is lymphocyte infiltration of the midbrain and basal ganglia. It is thought that there may be an autoimmune component, possibly triggered after a viral infection.
Autoantibodies reactive against human basal ganglia antigens present in the majority of encephalitis lethargica patients.
Brain MRI demonstrates inflammatory changes localized to the deep grey matter
in 40% of patients.
- T1: low signal
- T2/FLAIR: high signal in the basal ganglia (including the substantia nigra), midbrain, thalamus, cerebral peduncle and/or temporal cortex
- T1 C+ (Gd): leptomeningeal and focal patchy enhancement
- DWI/ADC: isointense without restriction of ADC
- PET-CT: increased glucose metabolism in the basal ganglia
Treatment and prognosis
Treatment approaches to encephalitis lethargica include immunomodulating therapies and steroids.
History and etymology
First described by Constantin Freiherr von Economo (1876-1931), a Romanian psychiatrist and neurologist, in 1916 during an epidemic affecting 500,000 people worldwide in 1916-1927 4,8. There have been no further epidemics of encephalitis lethargica since the 1920s, although sporadic cases have continued to be reported 7.
In 1973, the book "Awakenings", by the Anglo-American neurologist Oliver Sacks (1933-2015) was published. The Hollywood film of the same name came out in 1990, starring, Robin Williams as Dr Sacks, and Robert De Niro as one of his patients. The book, and movie, documented a group of postencephalitic patients in a long term care facility and their initial miraculous response to L-DOPA 5-7.
General imaging differential considerations include: