Measles encephalitis

There are different forms of measles encephalitis which occur at different times in relation to the onset of rash:

• post-infectious encephalomyelitis occurs at around one week after onset of the rash
  • infectious virus is rarely found in the brain
  • condition is associated with demyelination and is thought to have an auto-immune basis
• acute measles encephalitis of the delayed type occurs in immunocompromised patients
  • may occur without a preceding measles-like illness although there may be a history of exposure to measles several weeks or months previously
  • characterised by acute neurological compromise and deterioration of consciousness, seizures and progressive neurological damage
• subacute sclerosing pancencephalitis
  • a rare, fatal, late complication of measles infection. One case of SSPE occurs for every 25,000 measles infections
  • in children infected under the age of two, the rate is one in 8000 infections
  • developing measles under one year of age carries a risk of SSPE 16 times greater than in those infected over five years of age
  • median interval from measles infection to onset of symptoms is around seven years but may be as long as two to three decades
  • SSPE may follow an unrecognised measles infection. Wild measles virus has been found in the brain of SSPE cases including those with no history of measles disease

Reference:

1. Immunisation Against Infectious Disease - "The Green Book".Chapter 21 Measles (August 2006)