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Dr Amir Rezaee and Dr Frank Gaillard et al.

Leptomeningitis, which are more commonly referred to as meningitis, refers to inflammation of the subarachnoid space (i.e. arachnoid mater and pia mater) caused by an infectious or noninfectious process.   


  • pyogenic meningitis
    • elderly
      • Streptococcus pneumoniae
      • Listeria monocytogenes
      • Neisseria meningitidis
      • Gram negative bacilli 
    • adults
      • Streptococcus pneumoniae
      • Neisseria meningitidis
      • Group B streptococcus
    • children
      • Neisseria meningitidis
    • infants
      • Streptococcus pneumoniae
      • Neisseria meningitidis
    • neonates
      • Group B streptococcus
      • Escherichia coli
      • Listeria monocytogenes
  • viral meningitis
    • Enterovirus
  • mycobacterial meningitis
  • fungal meningitis

For a further discussion related to other aetiological agents and other infective processes in the CNS, please refer to CNS infectious diseases

Aseptic meningitis

Radiographic features

  • may be normal
  • subtle hydrocephalus
  • hyperdensity around basal cisterns (especially in tuberculosis
  • leptomeningeal enhancement
  • complications or sources of the meningitis
  • T1: may be normal; sulci may appear less hypointense than normal
  • T1 C+ (Gd): leptomeningeal enhancement
  • FLAIR: demonstrates hyperintense signal in CSF space, especially in the sulci
  • FLAIR C+ (Gd): has shown to be more sensitive and specific than T1 C+ (Gd) sequence in spotting leptomeningeal enhancement 6
  • MR angiography: arterial narrowing or occlusion


The complications of meningitis can be remembered using the mnemonic HACTIVE.

See also

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