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Encephalitis Lethargica

Encephalitis lethargica (EL) is a form of encephalitis which is largely characterized by sleep and movement disorders, and postencephalitic parkinsonism in survivors. It is a rare disease. Notably, between 1917 and 1926, there was an outbreak of EL.


Encephalitis lethargica (EL) is a rare form of encephalitis that garnered attention during an epidemic of the disease between 1917 and 1926. The cause of EL is still not known [1]. It is sometimes referred to as the sleepy sickness or sleeping sickness.

The illness was mainly characterized by lethargy and somnolence, although there were significant variations in presentation. Some patients presented with insomnia, mania, psychosis, or even coma. Patients with EL suffered for years. It was estimated that the disease affected over a million people [2] [3].

Common clinical features included movement disorders which in the acute phase of the illness included muscular rigidity, tremor, and abnormal eye movements. Other associated manifestations were fever, visual disturbances, myalgias, weakness, and slow physical and cognitive functioning. In patients that survived the disease, one of the most prominent sequelae was postencephalitic parkinsonism (PEP). PEP could be distinguished from Parkinson's disease (PD) based on an early age of onset and because the associated tremor was not the typical pill-rolling tremor seen in PD. PEP also caused pyramidal signs and respiratory distress.

Since the aforementioned epidemic, there have been a few sporadic cases recorded [2]. Speculations about the etiology of EL have mostly revolved around a possible link with the Spanish influenza virus that caused a pandemic around the same time as EL. Some atypical enteroviruses have also been suspected. EL is diagnosed clinically, although there are brain changes that can be visualized by magnetic resonance imaging (MRI). There were as many as 28 proposed types of the disease, based on clinical presentation and symptomatology [4].

  • He had almost recovered when he developed fatigue and hypersomnia and was diagnosed with encephalitis again, supported by mild pleocytosis in cerebrospinal fluid and subcortical white matter lesions in the frontal lobes.[ncbi.nlm.nih.gov]
  • Ward, On doing nothing: Descriptions of sleep, fatigue, and motivation in encephalitis lethargica, Movement Disorders, 26, 4, (599-604), (2011). David J. Burn, Commentary on the postencephalitic cases of Dr.[oadoi.org]
Intermittent Fever
  • He was diagnosed with encephalitis lethargica with somnolence, akinetic mutism, and ophthalmoplegia after intermittent fever. Cerebrospinal fluid pleocytosis and positive oligoclonal bands were documented.[ncbi.nlm.nih.gov]
Respiratory Abnormalities
  • The diagnostic clinical criteria for EL like illness include subacute hypersomnolence and ophthalmoparesis followed by Parkinsonism, oculogyric crisis, neuropsychiatric disorders and central respiratory abnormality.[ncbi.nlm.nih.gov]
  • The chronic phase was characterized by parkinsonism, but sleep disturbances, oculomotor abnormalities, involuntary movements, speech and respiratory abnormalities, and psychiatric disorders were also common features.[academic.oup.com]
Persistent Vomiting
  • Clinical features of note were a presentation with vertigo, persistent vomiting and sleep disturbance including marked daytime somnolence and vivid nightmares.[ncbi.nlm.nih.gov]
  • She went on to develop gross supranuclear gaze palsy, neck rigidity, bradykinesia, blepharospasm, profound somnolence and anarthria but no tremor, weakness or impairment of cognition. She died after an illness lasting 12 months.[ncbi.nlm.nih.gov]
  • Dyskinesias In addition to parkinsonism, 11 patients had evidence of dyskinetic movement disorders: dystonia ( n 6, of whom five had generalized dystonia); chorea/hemiballismus ( n 2); motor tics ( n 2); stereotypies ( n 2); facial grimacing and blepharospasm[brain.oxfordjournals.org]
Motor Restlessness
  • He suffered extreme motor restlessness, dystonic posturing, intractable blinking, and compulsive touching of his body. He became progressively more bradykinetic with a stooped gait and developed rest tremor. There was no rigidity.[brain.oxfordjournals.org]
  • Persistence of enterovirus RNA in muscle biopsy samples suggests that some cases of chronic fatigue syndrome result from a previous, inflammatory viral myopathy.[ncbi.nlm.nih.gov]
  • A 10-year-old boy presented with fever, headache, vomiting, and hypersomnolence. An akinetic-rigid syndrome with tremor, dysphagia, dysphonia, and sialorrhea, as well as pyramidal signs, developed.[ncbi.nlm.nih.gov]
  • Definition Encephalitis lethargica is a disease characterized by high fever, headache, double vision, delayed physical and mental response, and lethargy. In acute cases, patients may enter coma.[ninds.nih.gov]
  • Last updated April 18, 2018 Encephalitis Lethargica (EL) is a disease characterized by high fever, headache, double vision, delayed physical and mental response, extreme tiredness (lethargy), and sometimes coma.[dovemed.com]
  • Summary of Case A 31 year-old female presented at our centre with headache and fever. She had suffered from a headache for about 3 weeks, and 2 weeks previously, her symptoms were aggravated by nausea and vomiting.[esciencecentral.org]
Vocal Tic
  • tic called klazomania Neck rigidity Behavioural changes including psychosis Causes The exact cause of this condition is not clear.[news-medical.net]
  • Klazomania (a vocal tic) is sometimes present.[en.wikipedia.org]
  • tics, stereotypies Mutism, catatonia, obsessive–compulsive disorder, trichillomania Hyperventilation 35, M Hypersomnolence Present Bradykinesia, rigidity, rest tremor – Obsessive–compulsive disorder, depression Ophthalmoplegia 69, M Sleep inversion Present[brain.oxfordjournals.org]
Pill Rolling Tremor
  • PEP could be distinguished from Parkinson's disease (PD) based on an early age of onset and because the associated tremor was not the typical pill-rolling tremor seen in PD. PEP also caused pyramidal signs and respiratory distress.[symptoma.com]
  • There were other clinical differences, including the absence in pEP of the characteristic “pill-rollingtremor of IP. pEP generally progressed more rapidly and in spurts, in contrast to the slow and steady progression of IP.[doi.org]
  • Occurrence of depression, mania, obsessive-compulsive disorder, and hyperactivity in post-encephalitic patients anticipated current concepts of the role of the basal ganglia in mood, personality, and obsessional syndromes.[ncbi.nlm.nih.gov]
  • Hyperactivity 2.6. Physical inertia 3. People Affected 3.1. More common in males under 40 3.2. Since the late 1500s, there have been scattered reports of outbreaks in Europe 3.3.[mindmeister.com]
  • Behavior disorders, resembling those of attention-deficit-hyperactivity and oppositional defiant disorders, and termed ’organic drivenness,’ were described as complications of encephalitis following the influenza pandemic of 1918 (Hohman, Ebaugh, 1922[pediatricneurologybriefs.com]
  • We describe 2 recent cases of EL characterized by an acute encephalitis with mixed movement disorders (dystonia-Parkinsonism plus stereotypy) and psychiatric disorders (agitated catatonia, coprolalia, and echo phenomena).[ncbi.nlm.nih.gov]


Although the diagnosis is clinical, there are measurable and observable changes in the nervous system. About half of patients with encephalitis lethargica have lymphocytes in their cerebrospinal fluid (CSF), as well as elevated proteins [5]. Autoantibodies against the basal ganglia cells are found in EL. Often there is evident grey matter inflammation on magnetic resonance imaging (MRI). Nuclear medicine has also been utilized for diagnostic purposes.

EL can be initially diagnosed as a psychiatric or neurological condition such as substance intoxication or epilepsy. Consequently, many patients with EL were regarded as having a psychiatric disorder before the diagnosis of EL became clear.

Literature has proposed certain criteria for the diagnosis of EL and these include acute or subacute encephalitis, flu-like symptoms, hypersomnia, ophthalmoplegia, and psychiatric symptoms. These features should be present with no other illness that could explain their existence.

Lymphocytic Infiltrate
  • Post-mortem examination in the two fatal cases showed changes of lymphocytic meningitis and focal diencephalic lymphocytic infiltration, although these changes were mild relative to the effects of the clinical illness.[ncbi.nlm.nih.gov]
  • 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.[radiopaedia.org]
  • Histopathology in one case demonstrated striatal encephalitis with perivenous B- and T-lymphocytic infiltration.[ndcn.ox.ac.uk]
  • Neuropathology of postencephalitic parkinsonism shows marked neuronal loss and gliosis throughout the brainstem, but particularly in the substantia nigra and, to a lesser extent, locus coeruleus.[academic.oup.com]
  • In contrast, pEP showed extensive and severe bilateral diffuse degeneration and gliosis of substantia nigra and locus ceruleus in the absence of Lewy bodies, with damage to other parts of the brainstem and widespread presence of globose neurofibrillary[doi.org]
White Matter Lesions
  • He had almost recovered when he developed fatigue and hypersomnia and was diagnosed with encephalitis again, supported by mild pleocytosis in cerebrospinal fluid and subcortical white matter lesions in the frontal lobes.[ncbi.nlm.nih.gov]


  • The effect of corticosteroid treatment remains controversial in encephalitis; however, some EL syndrome patients exhibit an excellent response to corticosteroid treatment.[ncbi.nlm.nih.gov]
  • José Fidel Baizabal‐Carvallo, Francisco Cardoso and Joseph Jankovic, Myorhythmia: Phenomenology, etiology, and treatment, Movement Disorders, 30, 2, (171-179), (2014).[oadoi.org]


  • Encephalitis lethargica associated with Parkinsonism in childhood is rare and usually carries a poor prognosis.[ncbi.nlm.nih.gov]
  • Prognosis The course of encephalitis lethargica varies depending upon complications or accompanying disorders. x Prognosis The course of encephalitis lethargica varies depending upon complications or accompanying disorders.[ninds.nih.gov]
  • Prognosis The course of encephalitis lethargica varies depending upon complications or accompanying disorders.[brainfacts.org]
  • What is the Prognosis for Encephalitis Lethargica? Prognosis of encephalitis lethargica varies but complete recovery occurs in just 20% of cases. Mortality rate in case of encephalitis lethargic is around 2% to 12%.[epainassist.com]


  • Cell Biology, Indiana University School of Medicine, Fort Wayne, Indiana 46805, USA. vilensk@ipfw.edu Abstract Postencephalitic parkinsonism has been considered unique among disorders with parkinsonian features because it is believed to have a unitary etiology[ncbi.nlm.nih.gov]
  • The precise etiology of this disorder remains a conundrum. Most investigators suspect a viral etiology.[indiana.pure.elsevier.com]


  • Abstract Since encephalitis lethargica's (EL) prevalence in the 1920s, epidemiologic and clinical debate has persisted over whether EL was caused by, potentiated by, or merely coincident with the Spanish influenza pandemic.[ncbi.nlm.nih.gov]
  • Clinically, epidemiologically, and morphologically they represent distinct entities, and EL has disappeared.[doi.org]
Sex distribution
Age distribution


  • Observations of deferred onset and "tardy" hyperkinesias presaged current theories of the pathophysiology of tardive dyskinesia.[ncbi.nlm.nih.gov]
  • Giovanni Fabbrini, Giovanni Defazio, Carlo Colosimo, Philip D Thompson and Alfredo Berardelli, Cranial movement disorders: clinical features, pathophysiology, differential diagnosis and treatment, Nature Clinical Practice Neurology, 10.1038/ncpneuro1006[oadoi.org]


  • Prevention of encephalitis lethargica is also possible by prevention of some related infections.[epainassist.com]
  • MacNalty thought the patients had a new disease, being unaware of von Economo’s publication because war prevented journal circulation.[n.neurology.org]
  • The NINDS supports research on disorders that affect the brain, such as encephalitis lethargica, with the goal of finding ways to prevent and treat them. (The disease was the subject of the book and film, “Awakenings.”)[neurologycolorado.com]
  • The patient is unable to prevent herself from falling asleep, even in the middle of performing a nose-touching manoeuvre. My first download was incomplete, thanks to the archivist for fixing the problem.[archive.org]



  1. Dourmashkin RR. What caused the 1918–30 epidemic of encephalitis lethargica? J R Soc Med. 1997;90(9):515–520.
  2. National Institute of Neurological Disorders and Stroke. Encephalitis Lethargica Information Page. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/All-Disorders/Encephalitis-Lethargica-Information-Page. Accessed October 11, 2017.
  3. Tappea D, Alquezar-Planas DE. Medical and molecular perspectives into a forgotten epidemic: Encephalitis lethargica, viruses, and high-throughput sequencing. J Clin Virol. 2014;61(2):189-195.
  4. Vilensky JA, Goetz CG, Gilman S. Movement disorders associated with encephalitis lethargica: a video compilation. Mov Disord. 2006;21(1):1-8.
  5. McCall S, Henry JM, Reid AH, Taubenberger JK. Influenza RNA not detected in archival brain tissues from acute encephalitis lethargica cases or in postencephalitic Parkinson cases. J Clin Neuropathol Exp Neurol. 2001;60(7):696–704.

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Last updated: 2019-07-11 20:43