Subacute sclerosing panencephalitis
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Subacute sclerosing panencephalitis (SSPE)—also known as Dawson disease—is a rare form of chronic, progressive
brain inflammation Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations ...
caused by slow infection with certain defective strains of hypermutated
measles virus ''Measles morbillivirus'' (MeV), also called measles virus (MV), is a single-stranded, negative-sense, enveloped, non-segmented RNA virus of the genus ''Morbillivirus'' within the family ''Paramyxoviridae''. It is the cause of measles. Human ...
. The condition primarily affects children, teens, and young adults. It has been estimated that about 2 in 10,000 people who get measles will eventually develop SSPE. However, a 2016 study estimated that the rate for unvaccinated infants under 15 months was as high as 1 in 609. No cure for SSPE exists, and the condition is almost always fatal. SSPE should not be confused with
acute disseminated encephalomyelitis Acute disseminated encephalomyelitis (ADEM), or acute Demyelinating disease, demyelinating encephalomyelitis, is a rare autoimmune disease marked by a sudden, widespread attack of inflammation in the brain and spinal cord. As well as causing the ...
, which can also be caused by the measles virus, but has a very different timing and course. SSPE is caused by the wild-type virus, not by vaccine strains.


Signs and symptoms

SSPE is characterized by a history of primary
measles Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than , cough, ...
infection, followed by an asymptomatic period that lasts 7 years on average but can range from 1 month to 27 years. After the asymptomatic period, progressive neurological deterioration occurs, characterized by behavior change, intellectual problems,
myoclonic seizures Myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching of a muscle or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus (myo "muscle", clonic "jerk") describes a medical sign and, generally, is ...
, blindness,
ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...
, and eventually death.


Progression

Symptoms progress through the following 4 stages: * Stage 1: There may be personality changes, mood swings, or depression. Fever, headache, and memory loss may also be present. This stage may last up to 6 months. * Stage 2: This stage may involve jerking, muscle spasms, seizures, loss of vision, and dementia. * Stage 3: Jerking movements are replaced by writhing (twisting) movements and rigidity. At this stage, complications may result in
blindness Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment†...
or death. * Stage 4: Progressive
loss of consciousness Loss may refer to: Arts, entertainment, and media Music * ''Loss'' (Bass Communion album) (2006) * ''Loss'' (Mull Historical Society album) (2001) *"Loss", a song by God Is an Astronaut from their self-titled album (2008) * Losses "(Lil Tjay son ...
into a
persistent vegetative state A persistent vegetative state (PVS) or post-coma unresponsiveness (PCU) is a disorder of consciousness in which patients with severe brain damage are in a state of partial arousal rather than true awareness. After four weeks in a vegetative stat ...
, which may be preceded by or concomitant with
paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...
, occurs in the final stage, during which breathing, heart rate, and blood pressure are affected. Death usually occurs as a result of
fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...
,
heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...
, or the brain’s inability to control the
autonomic nervous system The autonomic nervous system (ANS), formerly referred to as the vegetative nervous system, is a division of the peripheral nervous system that supplies viscera, internal organs, smooth muscle and glands. The autonomic nervous system is a control ...
.


Pathogenesis

A large number of
nucleocapsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...
s are produced in the
neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...
s and the
glial cell Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form mye ...
s. In these cells the viral
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s that encode
envelope protein A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes. Numerous human pathogenic viruses in circulation are encase ...
s have restricted expression. As a result, infectious particles like the M protein are not produced, and the virus is able to survive persistently without evoking an immune response. Eventually the infection will lead to SSPE.


Diagnosis

According to the
Merck Manual ''The Merck Manual of Diagnosis and Therapy'', referred to as ''The Merck Manual'', is the world's best-selling medical textbook, and the oldest continuously published English language medical textbook. First published in 1899, the current print e ...
:
"SSPE is suspected in young patients with dementia and neuromuscular irritability. EEG, CT or MRI, CSF examination, and measles serologic testing are done. EEG shows periodic complexes with high-voltage diphasic waves occurring synchronously throughout the recording. CT or MRI may show cortical atrophy or white matter lesions. CSF examination usually reveals normal pressure, cell count, and total protein content; however, CSF globulin is almost always elevated, constituting up to 20 to 60% of CSF protein. Serum and CSF contain elevated levels of measles virus antibodies. Anti-measles IgG appears to increase as the disease progresses. If test results are inconclusive, brain biopsy may be needed."


Treatment

If the diagnosis is made during stage 1 it may be possible to treat the disease with oral
isoprinosine Inosine pranobex ( BAN; also known as inosine acedoben dimepranol (INN) or methisoprinol) is an antiviral drug that is a combination of inosine and dimepranol acedoben (a salt of acetamidobenzoic acid and dimethylaminoisopropanol) in a ratio of ...
(Inosiplex) and intraventricular
interferon alfa Interferon alfa (INN) or HuIFN-alpha-Le, trade name Multiferon, is a pharmaceutical drug composed of natural interferon alpha (IFN-α), obtained from the leukocyte fraction of human blood following induction with Sendai virus. Interferon alfa conta ...
, but the response to these drugs varies from patient to patient, and the only accepted treatments are supportive measures such as
anticonvulsants Anticonvulsants (also known as antiepileptic drugs or recently as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of b ...
. Following onset of stage 2, the disease is invariably fatal.


Prognosis

In the classic presentation of the disease death occurs in 1 to 3 years, but faster and slower progressions can occur. Faster deterioration in cases of acute fulminant SSPE leads to death within 3 months of diagnosis. Although the prognosis is bleak for SSPE past stage 1, there is a 5% spontaneous remission rate—this may be either a full remission that may last many years or an improvement in condition giving a longer progression period or at least a longer period with the less severe symptoms. * *


Epidemiology

SSPE is a rare condition, although there is still relatively high incidence in Asia and the Middle East. However, the number of reported cases is declining since the introduction of the measles vaccine—eradication of the measles virus prevents the SSPE mutation and therefore the progression of the disease or even the initial infection itself.


References


Further reading

*


External links

* * *
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Subacute sclerosing panencephalitis
* {{DEFAULTSORT:Subacute Sclerosing Panencephalitis Inflammations Rare diseases Viral encephalitis Measles Neurodegenerative disorders Unsolved problems in neuroscience Slow virus diseases Rare infectious diseases de:Masern#Subakute sklerosierende Panenzephalitis