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Sub acute sclerosing panencephalitis

Sub acute sclerosing panencephalitis (SSPE) (also known as Dawson disease) is a rare chronic, progressive and fatal encephalitis that affects primarily children and young adults, caused by a persistent infection of immune resistant measles virus.

Epidemiology 

Only 1 in 100,000 people infected with measles develop SSPE, with a latency of typically a decade 2 (4 and 23 years 1) and thus a typical age of onset of 9 - 13 years of age 2. The marked decline of SSPE in first world nations is yet another example of the benefit of widespread vaccination.

Clinical presentation

Clinical presentation is gradual, progressive neuropsychological deterioration, consisting of personality change, seizures, myoclonus, ataxia, photosensitivity, ocular abnormalities, spasticity, and coma.

Pathology

Histopathologically, SSPE demonstrates the same changes seen in other chronic viral cerebral infections, such as HIV encephalitis and post-infectious encephalomyelitis 2.

Markers

CSF analysis : may show elevated levels of 

  • gammaglobulin
  • anti measles anti bodies.
EEG 
  • a characteristic "burst-suppression" pattern is often seen

Radiographic features

Features depend on the stage of disease. In the acute setting patchy asymmetric regions of white matter involvement are present, typically in the temporal and parietal lobes. Gradually more extensive white matter involvement develops with additional involvement of the corpus callosum and basal ganglia. Eventually a generalised encephalomalacia develops 1 and parenchymal loss may be seen in later stages. 

  • T1 C+ (GAD) : enhancement of affected regions may occur early in the course of the disease.
MR spectroscopy

May demonstrate 1:

  • decreased NAA : from neuronal loss
  • increases in choline : from demyelination
  • increase myo-inositol : from active gliosis
  • elevated lactate : from macrophagic infiltration

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