Encephalitis lethargica (EL) is a rare disease that is also known as von Economo encephalitis. It affects the midbrain and basal ganglia, and the exact aetiology is unknown.
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 aetiology is unknown but there is lymphocyte infiltration of the midbrain and basal ganglia.
Autoantibodies reactive against human basal ganglia antigens present in the majority of EL patients.
Brain MRI demonstrates inflammatory changes localised 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 von Economo in 1916 during an epidemic affecting 500,000 people worldwide in 1916-1927. There have been no further epidemics of EL since the 1920s, although sporadic cases have continued to be reported.
General imaging differential considerations include:
- 1. K. von Economo. Encepahlitis lethargica. Wiener klinische Wochenschrift, May 10, 1917, 30: 581-585. Die Encephalitis lethargica. Leipzig and Vienna, Franz Deuticke, 1918
- 2. Dale RC, Church AJ, Surtees RA et-al. Encephalitis lethargica syndrome: 20 new cases and evidence of basal ganglia autoimmunity. Brain. 2004;127 (1): 21-33. doi:10.1093/brain/awh008 - Pubmed citation
- 3. Morris S. Dickman, MD von Economo Encephalitis Arch Neurol. 2001; 58; 1696-1698
- 4. Lopez-Alberola R, Georgiou M, Sfakianakis GN et-al. Contemporary Encephalitis Lethargica: phenotype, laboratory findings and treatment outcomes. J. Neurol. 2009;256 (3): 396-404. doi:10.1007/s00415-009-0074-4 - Pubmed citation