26. Purulent meningitis
Staining: HE
Organ: Brain + meninges
Description:
Two types of tissue can be seen: eosinophilic brain parenchyme containing neurons and a basophilic exudate surrounding it.
The exudate contains many neutrophils. Some places the exudate “infiltrates” into the parenchyme slightly.
Diagnosis: Purulent meningitis
Theory:
While there are some places where the exudate appears to infiltrate into the brain parenchyme, it’s actually in the perivascular space and not inside the parenchyme. There is no inflammation of the brain, so no encephalitis. The inflammation is only of the meninges.