Subacute-sclerosing panencephalitis (SSPE) is a persistent infection of the brain with measles virus, occurring in children and young adults. It is a type of viral encephalitis meaning the brain becomes irritated and swollen. It usually occurs a long time after measles infection, developing between 6 to 12 years after the initial infection with the virus. Cases can also follow immunisation with measles vaccine but this is much less common than after natural measles. The incidence of SSPE following natural measles infection is approximately 4 to 11 cases per 100,000 people. The incidence after measles immunisation is less than 1 case per 1,000,000.
Last updated September 2020 by Dr A Riordan, Consultant Paediatrician, Alder Hey Children’s Hospital, Liverpool, UK.
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The onset of the illness is subtle. The first signs are behavioural disturbances or a decline in school performance. Progression of the illness will vary from child to child, but evidence that this is a more serious illness usually begins with loss of motor control (ability to move around) and coordination. This often starts with characteristic jerking movements, which may at first appear as clumsiness. These jerking movements are known as myoclonic seizures. Tonic clonic seizures (falling to the floor and limbs jerking) may also occur. As the condition worsens, problems with swallowing, speech and vision may occur. SSPE can be life-threatening.
Sadly the majority of children die within 5 to 10 years after the onset of symptoms. Children who survive may do so with considerable intellectual and physical impairment.
The exact causes of SSPE are not known. Most children who develop SSPE are known to have had an attack of measles, usually many years before. The risk of developing SSPE is greater if children have measles when aged less than one year old or if they are immune suppressed.
Blood tests and a lumbar puncture will be carried out if SSPE is suspected, and MRI scans may show changes to the brain. An electroencephalogram (EEG) may show characteristic periodic activity (Rademecker complex).
There is no cure for SSPE, antiviral drugs and drugs that boost the immune system may slow the progression of the disease. Treatment with Inosiplex (isoprinosine) may be of benefit in slowly progressive cases. Occasionally, more aggressive treatments may be used, including antivirals (ribavirin) and immune modulating drugs (interferons). These can be injected into the fluid around the brain (intrathecal therapy), which may help to reduce the inflammation. These treatments have rarely been shown to recover loss of function and have side effects, but they may stabilize the disease for several years.. It is possible that with further research new drugs that might reduce or ‘dampen down’ the brain’s response to the re-activation of the measles virus may eventually be found. Medication to control seizures and reduce muscle stiffness can improve the child’s quality of life.
Information and support in the UK for subacute-sclerosing panencephalitis is provided by the Encephalitis Society (see entry Encephalitis).