Post-encephalitic parkinsonism is a disease believed to be caused by a viral illness that triggers degeneration of the nerve cells in the
substantia nigra
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra app ...
. Overall, this degeneration leads to clinical
parkinsonism
Parkinsonism is a clinical syndrome characterized by tremor, bradykinesia (slowed movements), rigidity, and postural instability. These are the four motor symptoms found in Parkinson's disease (PD), after which it is named, dementia with Lewy bo ...
.
Historically, starting in 1917 an epidemic of
encephalitis lethargica
Encephalitis lethargica is an atypical form of encephalitis. Also known as "sleeping sickness" or "sleepy sickness" (distinct from tsetse fly-transmitted sleeping sickness), it was first described in 1917 by neurologist Constantin von Economo a ...
, also called von Economo's encephalitis or "sleepy-disease" occurred, possibly related to the 1918
Spanish flu
The 1918–1920 influenza pandemic, commonly known by the misnomer Spanish flu or as the Great Influenza epidemic, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was ...
pandemic; however, even with the use of modern molecular diagnostic tests on appropriate corpses, no firm link between encephalitis lethargica with influenza has been made. Although parkinsonism was occasionally seen during the acute
encephalitic phase of encephalitis lethargica, it was often encountered in the post-encephalitic phase. The onset of post-encephalitic
parkinsonism can be delayed by several years from the resolution of encephalitis lethargica.
The brain regions affected contain
neurofibrillary tangles
Neurofibrillary tangles (NFTs) are aggregates of hyperphosphorylated tau protein that are most commonly known as a primary biomarker of Alzheimer's disease. Their presence is also found in numerous other diseases known as tauopathies. Little is k ...
, similar to those seen in
Alzheimer's disease
Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
. Nevertheless, the senile plaques common in Alzheimer's disease are not found.
References
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External links
{{Diseases of the nervous system
Extrapyramidal and movement disorders