There are multiple ways to categorize CNS infections:

• anatomically
• aetiologically
• based on age group
• based on risk factors

The anatomical approach:

• Meningitis
  • Inflammation of the meninges
  • Mostly viral or bacterial
• Encephalitis
  • Inflammation of brain parenchyma
  • Mostly viral
• Meningoencephalitis
  • Inflammation of both meninges and brain tissue
• Myelitis
  • Inflammation of the spinal cord
• Space occupying mass lesion
  • Bacterial, fungal or parasitic
• Neurosurgery-related infection
  • Bacterial

The aetiological approach:

• bacteria - there are various bacteria that can cause CNS infections

Neurosyphilis – NOT generally diagnosed through microscopy

Acid-fast bacilli (TB)

• viruses -enterovirus, herpes simplex virus, varicella zoster virus, mumps virus (look at virology lecture)
• fungi- cryptococcal meningitis or locally invasive fungal infections (e.g. from sinusitis)