Central Nervous System Inflammation Overview

Introduction

• Although the CNS is well protected, its defences against organisms that have already invaded are less well developed. This is due to:
  1. Minimal antibody production
  2. Cerebrospinal fluid providing a good culture medium for invading organisms.
  3. Inflammatory cell, antibody and drug entry to the CNS being impeded by the blood-brain barrier.

Classification of Inflammation

• CNS inflammation may manifest as encephalitis or meningitis.
  • These often co-exist.
• The aetiology CNS inflammation may be:
  • Infectious
    • Bacteria
    • Fungi
    • Protozoa
    • Viruses or non-infectious.
    • Infectious agents vary geographically.
  • Non-infectious
    • No infectious cause can be found in 60% of meningitis cases.
• Inflammation may also be broadly classified based on the nature of the exudate present.
  • Fibrinous
    • Caused by bacteria infection (including Mycoplasma).
  • Suppurative
    • Caused by bacteria and fungi.
  • Granulomatous
    • Caused by bacteria or fungi.
  • Lymphoplasmacytic
    • Caused by viruses.
  • Haemorrhagic
    • This is rare.
    • Usually associated with septicemia or infarcts.

Clinical Signs of CNS Inflammation

• Signs often reflect multiple levels of neurological involvement.
• Generalised forebrain signs are seen.
• Neck pain may be seen alone, or with other signs.

Diagnosis

• History, physical and neurological examination.
• Fundic examination may give clues as to whether a systemic infection is present.
• CSF examination may help define the problem.

Treatment

• Treatment is directed at a specific cause, if one can be found.
  • If a cause cannot be found, trimethoprim, clindamycin or doxycycline plus or minus corticosteroids may be used.