III. Meningitis (Leptomeningitis)
C. Pathological changes:
1. Acute pyogenic meningitis (usually bacterial):
- Purulent exudate in subarachnoid space and along vessels, includes neutrophils and bacteria; the severity of the exudate varies with the organism
- Inflammatory infiltrate in walls of arteries and veins (vasculitis); in severe cases ischemia may result from subsequent thrombosis
- Cellular infiltration of cranial nerves and spinal roots
- Edema may occur in brain tissue
2. Acute aseptic (viral) meningitis: lymphocyte infiltrate; mild |