Definition: A form of bacterial meningitis characterized by the presence of pus in the subarachnoid space.
Features:
Intense neutrophilic (polymorphonuclear) inflammatory response
Thick exudate in CSF
Turbid or cloudy CSF appearance
CSF findings:
↑↑ White blood cells (neutrophils)
↓ Glucose (hypoglycorrhachia)
↑ Protein
High opening pressure
Usually caused by: pyogenic bacteria (e.g., S. pneumoniae, H. influenzae, N. meningitidis)
In short: Meningitis is the umbrella term.
Purulent meningitis is a severe, bacterial subtype with pus formation and high inflammatory burden.